Head & Neck Surgery - Otolaryngology
4th Edition

141
Surgery of the Mastoid and Petrosa
Richard A. Chole
Hilary A. Brodie
Abraham Jacob
History
Surgery of the mastoid and petrosa developed as a treatment for suppurative ear disease (1). Infections of the ear were recorded as early as 380 BC in the Hippocratic Canon. Near the turn of the 16th century, Fabricius Hildanus reported a case of spontaneous drainage from a postauricular abscess for which he advocated early incision and drainage. Riolan the Younger described a procedure akin to mastoidectomy in 1649, and John Luis Petit performed the first surgical trephination of the mastoid in 1774. Petit described exposing the mastoid cortex, performing a trephination, and then enlarging the surgically created fistula. J.G.H. Fielitz reported five such cases in 1785. The procedure fell into disrepute, however, after the sensational death of the Danish physician Johanne Gust Von Berger in 1792. He died of meningitis 12 days after a mastoidectomy performed by Koelpin and Callisen. Fortunately, however, Schwartze repopularized the operation in 1873. Since then, technologic advancements such as the operating microscope, the high-speed drill, and specialized microsurgical instruments have led to significant advances in the treatment of mastoid disease. Regions of the skull base previously thought to be inaccessible such as the petrous apex, the course of the facial nerve, the endolymphatic sac, and the cerebellopontine angle were now within reach. Indications for these procedures (Table 141.1) include acute otologic infections (Chapter 138), chronic infections with or without cholesteatoma (Chapters 138 and 140), trauma (Chapter 139), facial nerve disorders (Chapter 144), vestibulopathy (Chapter 156), and tumors of the skull base (Chapter 136).
Surgical Technique: Mastoidectomy
Incisions
The two principal incisions used for access to the mastoid cortex are the postauricular incision of Wilde and the endaural incision of Lempert. The postauricular incision provides better overall exposure and allows complete access to the mastoid tip. In adults, the incision is placed 8 to10 mm posterior to the postauricular sulcus where it is hidden by the pinna. This incision can be placed more posteriorly for wider exposure as might be necessary during translabyrinthine access to the cerebellopontine angle. It should not be placed directly in the postauricular crease, however, because this creates a deep, difficult to clean postauricular furrow. In children younger than 2 years, the inferior portion of this incision must be placed more posteriorly than in adults (Fig. 141.1). This is because the tympanic ring in children is underdeveloped, mastoid pneumatization is incomplete, and the stylomastoid foramen is quite shallow. Therefore, the facial nerve is vulnerable to injury. The surgeon should also keep in mind that congenital anomalies of the temporal bone can result in highly variable facial nerve position.
The postauricular incision is first outlined with a marking pen and infiltrated with a mixture of local anesthetic and epinephrine. The skin and subcutaneous tissues are incised sharply down to the temporalis fascia (superior to the inferior temporal line) and down to the periosteum overlying the mastoid cortex (inferior to the inferior temporal line). The ear flap is elevated anteriorly to identify the posterior edge of the external ear canal. Additional elevation
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superior to the ear canal exposes the root of the zygoma. Posterior to the ear canal, the postauricular muscle and pericranial soft tissues are incised and elevated in the same plane as described above. This dissection is carried to the mastoid tip. Care must be taken not to dissect anterior to the tip because this endangers the facial nerve in the stylomastoid foramen. Unless the mastoid tip is to be removed, the sternocleidomastoid muscle’s insertion onto the tip should not be severed. This minimizes postoperative discomfort. Thus far, the skin and soft tissues of the pinna have been laid anteriorly, but the periosteum still remains attached to the mastoid cortex.
TABLE 141.1 CLINICAL INDICATORS FOR MASTOIDECTOMY
Strategy
Indicators (one of the following)
   Persistent or recurrent otorrhea
   Persistent or recurrent ear pain
   Conductive hearing loss
   Tympanic membrane perforation and/or cholesteatoma
   Acute mastoiditis with osteitis
   Neoplasm of temporal bone
   Fracture of temporal bone with CSF leak
   Facial nerve paralysis requiring decompression of the facial nerve
Laboratory tests (as indicated)
Audiogram
Other tests (as indicated)
Type of anesthesia (as indicated)
Location of service (as indicated)
Process
Criteria for discharge
   Recovery from anesthesia
   Absence of significant vertigo
   Absence of signs of meningitis or toxic shock syndrome
Outcome
Results
Follow-up
   Healing of mastoid cavity if present
   Healing of surgical wound
   Resolution of presenting symptoms
   Evaluation of hearing
CSF, cerebrospinal fluid.
The American Academy of Otolaryngology–Head and Neck Surgery and the American Society for Head and Neck Surgery have published Clinical Indicators for surgical procedures. These Clinical Indicators are educational statements that have been drafted to assist surgeons in their practice and to promote discussion. These Indicators are not practice guidelines nor do they represent standards of practice with which individuals must conform.
The mastoid cortex is now exposed to start the drilling process. A T-shaped incision is made through the soft tissues and periosteum overlying bone. The superior limb of the “T” is placed along the inferior temporal line (inferior margin of the temporalis muscle) starting at a point just superior to the anterior-superior ear canal. This incision extends posteriorly as far as is needed for adequate exposure. Aninferior limb to the “T” is fashioned from the mastoid tip to the superior limb just described. Periosteal elevators are then used to elevate the periosteum of the mastoid cortex toward the posterior margin of the ear canal (Fig. 141.2). Superior to the ear canal, the periosteum should be elevated anteriorly along the zygomatic root. Inferior to the ear canal, the surgeon should elevate periosteum to the anterior margin of the superior aspect of the mastoid tip. If the tip is to be removed, the surgeon must remove all the periosteum from its surface. Taking a few moments to get this anterior extension superiorly and inferiorly will allow the ear to be held forward easily when using self-retaining retractors. The periosteum can also be elevated somewhat down the ear canal to release tension and prevent a canal laceration.
Figure 141.1 Placement of postauricular incisions in adults (A) and infants (B).
The suprameatal spine of Henle marks the lateral extent of the posterior-superior bony ear canal. Self-retaining retractors should be placed to hold the auricle forward. The surgeon has raised two anteriorly based flaps: (a) the pinna and subcutaneous tissues and (b) the deeper musculoperiosteal tissues. This deeper flap can be used to partially obliterate the mastoidectomy cavity at the end of a canal-wall-down mastoidectomy (2). After an intact canal wall mastoidectomy, however, both layers should be closed to maintain a patent meatus and a properly positioned auricle.
Endaural incisions were first described by Kessel in 1885 and later popularized by Lempert (3) in 1938. These incisions expose a limited portion of the mastoid cortex. First, a posterior canal wall incision is made from the 12-o’clock to the 6-o’clock position just medial to the bony cartilaginous junction (Lempert I incision). From the 12-o’clock position of the Lempert I incision, a medial to lateral incision is
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made into the incisura between the tragus and root of the helix (Lempert II incision). A relaxing incision is then made at the inferior margin of the Lempert I incision (in a medial to lateral direction). This allows the posterior ear canal and conchal skin to be mobilized (Fig. 141.3). The skin, soft tissues, muscle, and periosteum over the mastoid cortex are elevated using Lempert elevators and a self-retaining retractor placed. Indications for this incision include simple mastoidectomy in very poorly pneumatized temporal bones, atticotomies, canalplasties, and in some tympanoplasties. The endaural incision is closed in a layered fashion approximating deep tissues and then skin.
Figure 141.2 The periosteum is elevated off the mastoid cortex, exposing the posterior wall of the external auditory canal.
Surface Landmarks
The inferior temporal line (linea temporalis) defines the inferior limit of the temporalis muscle and provides a topographic landmark for the floor of the middle cranial fossa. Inferior to the temporal line is a protuberance atthe posterosuperior margin of the ear canal called the suprameatal spine of Henle. Macewen triangle (cribrose area) is a depressed pit just posterior to the spine of Henle and serves as a topographic landmark for the underlying mastoid antrum. The antrum is typically located 15 mm medial to the cribrose area. The zygomatic root is palpable superior to the ear canal. The bony ear canal is made up of both tympanic and squamous bone. The anterior, inferior, and posterior-inferior walls of the external auditory canal are formed by the tympanic bone. The region between the tympanosquamous and tympanomastoid suture lines (i.e., the posterior-superior bony ear canal) is made of squamous bone. The canal skin in this region is thicker and more vascular than the inferior canal skin. When creating a laterally based conchal flap, this thickened “vascular strip”
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is elevated and preserved. The surface anatomy of the adult and young child’s temporal bone differs. Children younger than 2 years have immature tympanic rings and poorly developed mastoids (Figs. 141.4 and 141.5). In children or adults with canal atresia, maldevelopment of the tympanic bone may result in a facial nerve that exits directly from what appears to be the mastoid cortex (4).
Figure 141.3 A: Endaural incision. B: Separation of bony cartilaginous junction. C: Mastoid exposure via an endaural incision.
Figure 141.4 Surface anatomy of the adult temporal bone.
Types of Mastoidectomy
The ear canal is made up of a cylinder of skin contained within a bony cylinder. In the normal ear, the tympanic membrane is the medial boundary for those cylinders. During routine office examination, it is not possible to see the epitympanum or mastoid region when the canal wall is intact. This is because the scutum blocks visualization of the epitympanum, and the posterior canal wall blocks access to the mastoid cavity. Therefore, removing the superior and posterior aspects of the bony canal allows direct access to the epitympanum and mastoid. This has the advantage of more thorough postoperative examination of the ear in the office. However, it leaves patients with cavities that require lifelong maintenance.
Figure 141.5 Surface anatomy of the infant temporal bone.
Mastoidectomy procedures can be categorized as canal-wall-up and canal-wall-down operations. Canal-wall-up procedures include the so-called simple mastoidectomy and the complete mastoidectomy with and without a facial recess approach. Canal-wall-down operations include the radical mastoidectomy, the modified radical mastoidectomy (MRM), and the Bondy MRM. The radical mastoidectomy removes the posterior and superior bony ear canal as well as the tympanic membrane, malleus, and incus. The stapes is usually preserved. The eustachian tube is packed, and no middle ear space remains. The entire cavity becomes lined with squamous epithelium. The radical mastoidectomy is “modified” when a tympanic membrane and mucosa-lined middle ear space are reconstructed. This is accomplished by placing a graft from the anterior annulus to the facial ridge. Ossicular reconstruction can also be performed during a MRM. The Bondy MRM is performed when disease spares the middle ear and only involves the epitympanum and mastoid. The scutum and posterior bony ear canal are removed to exteriorize the antrum and epitympanum, but the middle ear is not entered. Tympanoplasty and ossicular reconstruction can be performed whether the canal wall is taken down or left intact.
Figure 141.6 Axial section of a right adult temporal bone. VII, seventh cranial nerve; VIII, eighth cranial nerve; APA, anterior petrous apex; Ca, carotid artery; CT, chorda tympani; EAC, external auditory canal; ET, eustachian tube; Fn, facial nerve; IAC, internal auditory canal; KS, Körner septum; LSC, lateral semicircular canal; PPA, posterior petrous apex; PSC, posterior semicircular canal.
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Simple Mastoidectomy
A simple mastoidectomy has limited usefulness; it is most commonly used to drain acute mastoid infections that do not respond to antibiotics. The procedure involves removing the mastoid cortex, drilling through the lateral air cells, and entering the antrum. The remainder of the air cell system is not drilled.
Complete Mastoidectomy
The complete mastoidectomy affords access to the antrum, attic, labyrinth, endolymphatic sac, and vertical segment of the facial nerve (Fig. 141.6). All the air cells along the tegmen, sigmoid sinus, facial nerve, and semicircular canals are removed. The epitympanum is made accessible though the aditus ad antrum, and the incus and head of the malleus can be inspected directly. The incus and the head of the malleus may be removed for greater access to the supratubal recess.
Using the postauricular incision, the ear is laid forward and the mastoid cortex exposed as described above. The temporal line, spine of Henle, cribrose area, and posterior ear canal are used as the initial landmarks for drilling. The location of the mastoid antrum can be approximated by the intersection of a horizontal and vertical line drawn tangential to the superior and posterior margins of the external auditory canal. A large cutting burr and suction/irrigation are used to begin the mastoidectomy. Cortical bone is removed inferior to the middle fossa dura (tegmen mastoideum); the posterior edge of the bony ear canal is delineated; and the sigmoid sinus is identified. It is important to widely saucerize the mastoidectomy bowl by removing any overhanging edges. This permits more light to enter the cavity and allows the surgeon to bring in his instruments at an angle rather than directly along his line of sight. After determining the level of the tegmen, all air cells lateral to the sigmoid sinus should be removed to see the blue hue of the sinus through thin bone. The sinodural angle, marking the posterior-superior limit of the mastoid cavity, is then opened. Drilling proceeds medially along the tegmen toward the epitympanum. Keeping this anterior-superior portion of the dissection as the deepest portion of the cavity avoids inadvertent injury to the facial nerve. Korner septum is a plate of bone lateral to the antrum, and it represents the posterior extension of the petrosquamous suture line within the mastoid (5) (Fig. 141.7). The superior aspect of Korner septum must be removed to enter the mastoid antrum. The floor of the antrum, the horizontal semicircular canal, is a vital landmark that must be clearly visualized (Fig. 141.8). The labyrinth, made of otic capsule bone, usually appears slightly yellow when compared with the surrounding (white) membranous bone.
Once the antrum is entered, the dissection moves anteriorly into the epitympanum to find the incus. The posterior ear canal must be thinned although excessive thinning may lead to delayed dissolution of this structure. Identifying the posterior incudal ligament (often seen as a white streak through thin bone just inferior to the fossa incudus) is a useful landmark. In addition, by flooding the antrum with clear irrigant, the surface of the fluid forms a lens that
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will bend light from the microscope and allow the surgeon to see the incus before actually coming upon it (Fig. 141.8). Touching the incus with a rotating burr must be avoided because transmission of high-frequency mechanical energy to the inner ear can cause sensorineural hearing loss. Once the body of incus is identified, removing the bone lateral to the ossicles (between the tegmen tympani and superior ear canal) opens the epitympanum. Carrying this dissection anteriorly will expose the head of the malleus.
Figure 141.7 Körner septum. A: Axial section view of Körner septum. B: Lateral surgical view of Körner septum. SS, sigmoid sinus.
Figure 141.8 Simple mastoidectomy. A: Axial section view of mastoid cavity. B: Lateral surgical view of mastoid cavity. Ct, chorda tympani; Dr, digastric ridge; Fn, facial nerve; LSC, lateral semicircular canal; PSC, posterior semicircular canal.
Having found the antrum, the horizontal semicircular canal, and the incus, attention can now be directed to finding the facial nerve. The bony external auditory canal is
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progressively thinned from a lateral to medial direction. As this dissection proceeds medially, facial recess air cells anterior to the facial nerve will be encountered. The second genu of the facial nerve is immediately anterior and inferior to the midpoint of the horizontal canal, just medial to the short process of the incus. A 4-mm diamond burr and copious irrigation are used to make wide strokes from the incus superiorly toward the stylomastoid foramen along the presumed course of the facial nerve. Adequate irrigation prevents thermal injury to the nerve. The nerve should be visualized through thin bone but not completely exposed. As the facial nerve is traced inferiorly, the branch-point of the chorda tympani nerve will be found (Figs. 141.8 and 141.9). The chorda can then be traced anteriorly and superiorly.
Figure 141.9 Facial recess approach. A: Axial view. B: Surgical view. Ct, chorda tympani; Fn, facial nerve; Fr, facial recess; LSC, lateral semicircular canal; PSC, posterior semicircular canal; SS, sigmoid sinus; SSC, superior semicircular canal.
All of the cells within the mastoid tip should be exenterated. The posterior belly of the digastric muscle inserts medially on the mastoid tip. Identifying the muscle through egg-shelled bone is referred to as the “digastric ridge,” which is actually a surgically created landmark (Fig. 141.8). The fascia enveloping the digastric muscle is continuous anteriorly with the fibrous tissue surrounding the facial nerve at the stylomastoid foramen. Therefore, following the digastric ridge anteriorly in the mastoid tip is one way to find the facial nerve. Infralabyrinthine (retrofacial) air cells are those cells medial to the facial nerve, superior to the jugular bulb, and inferior to the posterior semicircular canal. They should be exenterated if disease is found within them or if either the jugular bulb or endolymphatic sac needs to be exposed.
Following a complete mastoidectomy the surgeon should thoroughly irrigate the cavity to remove bone dust, which may otherwise result in ossicular fixation. The complete mastoidectomy cavity should consist of a well-defined tegmen tympani and tegmen mastoideum superiorly, a clearly delineated sigmoid sinus posteriorly, an open sinodural angle, well-visualized semicircular canals, an intact posterior ear canal wall, and the facial nerve seen through thin bone.
Complete Mastoidectomy with a Facial Recess Approach
The facial recess is an aerated extension of the posterior-superior middle ear space. Medial to the tympanic annulus and lateral to the fallopian canal, it allows access to the middle ear from the mastoid cavity. Some surgeons use the term “posterior tympanotomy” to describe a facial recess approach. The facial recess is a triangular opening bordered posteromedially by the facial nerve, anterolaterally by the chorda tympani nerve, and superiorly by the fossa incudis (Fig. 141.9). An open facial recess provides access to the ossicles, stapedial tendon, round window, tympanic segment of the facial canal, and cochleariform process (6).
There are numerous indications for performing a posterior tympanotomy. These include transmastoid cochlear implantation, presence of cholesteatoma within both the middle ear and mastoid, chronic otomastoiditis with
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granulation tissue or cholesterol granuloma, and tumors within the middle ear and mastoid.
In the anterior epitympanum, a projection of bone extending inferiorly from the tegmen tympani (the cog) can obscure disease in the supratubal recess (7). The presence of granulation tissue, cholesteatoma, or tumor in the anterior epitympanum and supratubal recess requires removal of the incus, head of the malleus, and the cog for exposure. The incudostapedial joint must first be disarticulated through the facial recess before removing the incus and malleus head. Opening the facial recess can also improve aeration of the mastoid by providing an alternate route for air from the eustachian tube to enter the mastoid (other than the aditus ad antrum). Inadequate aeration or loculation of the mastoid cavity may result in recurrent retraction pocket formation, mucocele formation, or chronic otomastoiditis. One way to test for adequate aeration of the mastoid cavity is to fill the middle ear with saline and watch for flow into the mastoid. When the incus has been removed, rarely is a facial recess approach required for aeration.
When thinning the posterior canal wall, the facial recess is encountered medially. It is first noted as a color change (darker appearing bone) anterior to the facial nerve just inferior to its second genu. The facial nerve lies medial and inferior to the tip of the short process of the incus. The second genu of the facial nerve usually forms an angle of 95 to 125 degrees; it usually makes a gentle curve rather than an abrupt turn. The nerve may descend directly through the mastoid in a caudal direction, or it may deviate from the vertical by 5 to 35 degrees. The temporal bone is a three-dimensional structure. The facial nerve travels laterally as it moves inferiorly through its vertical segment. The nerve is lateral to the posteroinferior tympanic annulus in 65% of cases (8).
The surgeon should be aware of potential facial nerve anomalies. Dehiscence of the facial nerve is reported to occur in 55% to 57% of temporal bones (9). The facial nerve is dehiscent approximately 50% of the time in its tympanic segment just superior to the oval window. Other areas of possible dehiscence include the geniculate ganglion, facial recess, tympanic sinus, and the retrofacial region inferior to the labyrinth. Bone erosion secondary to cholesteatoma may also create dehiscence in the fallopian canal. Before encountering the nerve, the vasa nervorum can be appreciated through the egg-shelled bone overlying the nerve. The most common site of injury to the facial nerve in mastoid surgery is inferior to the lateral semicircular canal just beyond the second genu (9).
TABLE 141.2 OPEN VERSUS CLOSED TECHNIQUES FOR MASTOIDECTOMY
  Advantages Disadvantages
Intact wall Physiologic tympanic membrane position Residual cholesteatoma may be occult
Deep middle ear Recurrent cholesteatoma may occur in attic
No mastoid bowl Delayed canal breakdown
Incomplete exteriorization of facial recess
Second stage often required
Canal-wall-down Residual cholesteatoma visible on follow-up Mastoid bowl maintenance can be a lifelong problem
Recurrent cholesteatoma is rare Middle ear is shallow and difficult to reconstruct
Total exteriorization of facial recess Position of pinna may be altered
Second stage sometimes required
At a variable point along its descent toward the stylomastoid foramen, the facial nerve gives off the chorda tympani nerve. This nerve travels in an anterior, superior, and lateral direction. Facial nerve anomalies can include a chorda that branches from the facial nerve after it exits from the stylomastoid foramen, a bifid facial nerve, or a nerve coursing through the middle ear space just inferior to the oval window (10). Once the chorda tympani nerve is identified, the bone between the chorda and the facial nerve may be removed with a small diamond burr and copious irrigation. This opens the facial recess (Fig. 141.9). If additional exposure is required, the chorda may be sacrificed and the facial recess extended inferiorly—an extended facial recess approach. Care must be taken to identify the fibrous annulus of the tympanic membrane and to avoid inadvertent injury to the eardrum or medial ear canal.
Intact Canal Versus Canal-Wall-Down Mastoidectomy
Both the open (canal-wall-down) and the closed (intact canal with facial recess) procedures have advantages and disadvantages. Judgment as to which procedure to perform depends on the nature of the disease, the reliability of the patient, and the experience of the surgeon (Table 141.2).
The intact canal wall approach offers several advantages over open (canal-wall-down) techniques. First, there is no mastoid cavity to care for. Patients with cavities often require regular office debridement, may have a difficult time fitting hearing aids, need to adhere to water precautions, and have meatoplasties that may be cosmetically unappealing. An intact canal procedure also allows for a more physiologic ossicular reconstruction with a deeper, better-aerated middle ear. Some authors, however, have found no significant benefit in
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hearing results for intact canal wall mastoidectomy compared with canal-wall-down procedures (11,12).
There are several potential disadvantages to the intact-canal-wall approach. First, there is an increased risk of residual or recurrent disease. Widely varying results using a canal-wall-up mastoidectomy have been reported in the literature. However, most of the larger series reveal residual cholesteatoma in 20% to 35% of cases and recurrent disease in 5% to 20% (12,13,14,15,16,17,18,19,20). This is in contrast to results for open procedures in which there is a 2% to 17% rate of residual disease and a 0% to 10% chance for recurrence (12–14,19–22). The most common site for residual disease is the sinus tympani (18). A second potential although uncommon problem with the intact canal wall procedures is delayed breakdown of the posterior canal wall. This is due to compromised blood supply from overthinning the bone. A third disadvantage is an inability to see the mastoid cavity in the office for surveillance. Some surgeons routinely perform a “second look” operation 6 to 12 months after the initial procedure. A staged ossicular reconstruction can also be done at that time. Careful patient selection is vital. Intact-canal procedures should be performed in reliable patients who will follow-up regularly in the office.
Radical Mastoidectomy
The radical mastoidectomy is the most aggressive of the open cavity mastoid procedures. The classical radical mastoidectomy involves a canal-wall-down mastoidectomy combined with complete removal of the tympanic membrane, annulus, malleus, incus, and all middle ear mucosa. The eustachian tube is stripped of mucosa and obliterated with packing (fascia, muscle or bone). The goal of radical mastoidectomy is to establish a dry, open cavity devoid of secretory epithelium. Before the advent of tympanoplasty, this radical procedure was by far the most common open procedure. However, it is rarely performed today. Most surgeons prefer to do a MRM with reconstruction of a middle ear space and sound conduction apparatus. If disease permits, a graft can be placed isolating the eustachian tube and round window from the middle ear, creating a cava minor reconstruction. However, there are still some indications for a radical mastoidectomy. These include unresectable cholesteatoma with extension down the eustachian tube, cholesteatoma with erosion into the cochlea or labyrinth, or patients who have had multiple failed MRMs.
Figure 141.10 Completed canal-wall-down modified radical mastoidectomy. A: Axial view.B: Surgical view with location of endolymphatic sac.
The procedure involves performing a complete (intact canal) mastoidectomy with identification of all the landmarks discussed previously. The superior and posterior canal walls are then removed with a cutting burr and suction-irrigation. Prior to encountering the ossicles, the incudostapedial joint is separated and the head of the malleus and incus are removed. The canal wall can then be lowered to the level of the facial nerve. The stapes is preserved. A diamond burr with copious irrigation is used as the facial nerve is approached. All the mastoid and middle ear mucosa is stripped, and the eustachian tube is packed with muscle, fascia, or synthetic materials. The mastoid tip is removed below to the level of the digastric ridge. Care should be taken to lower the facial ridge, remove overhanging edges, and lower the inferior canal wall so as to prevent a dependent mastoid tip. To reduce the depth of the cavity, the perimeter is well saucerized.
Modified Radical Mastoidectomy
The radical mastoidectomy operation has been “modified” when a middle ear space is reconstructed (Fig. 141.10). The
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MRM begins with a complete mastoidectomy. The decision to take the canal wall down is then based on the extent of disease (Table 141.2). Most of the bone lateral to incus can be removed quickly with a large cutting burr and the scutum made flush with the anterior canal wall. Because the facial nerve is medial to the incus, it is protected. The bone immediately lateral to the ossicles must be removed carefully with microinstruments rather than the drill. This avoids direct contact between the rotating burr and ossicular chain. Alternately, the incudostapedial joint may be separated and the incus and head of the malleus removed. The posterior and inferior portions of the remaining ear canal are then removed. The bone, lateral to the facial nerve, called the “facial ridge,” is drilled down to the level of the nerve.
A few technical points deserve mention. Once the bulk of the posterior ear canal has been removed with cutting burrs, the vertical segment of the facial nerve is found by lowering the facial ridge with a diamond burr. The nerve should be seen through thin bone. Actual exposure of the facial nerve should be avoided, however, because this puts it at risk. With radical mastoidectomies and MRMs, the mastoid cortex must be well saucerized and the mastoid tip removed. This precludes a deep cavity with overhanging edges that can be difficult to cleanse. Saucerization makes the cavity shallow by allowing surrounding soft tissues to prolapse inward. The inferior portion of the tympanic ring should be lowered so it is flush with the hypotympanum. This prevents the formation of a dependent mastoid tip that collects debris. An anterior canal wall canalplasty should be performed to better expose the anterior tympanic sulcus. An incision is made in the anterior canal wall just lateral to the tympanic annulus, the skin is raised in a retrograde manner back to the bony cartilaginous junction, and the bone sculpted as necessary. One should use a large diamond burr with constant suction-irrigation to avoid entering the glenoid fossa.
After mastoid surgery has been completed, the middle ear space is reconstructed. A fascia graft is laid from the anterior annulus to and over the facial ridge. The graft must be well supported by absorbable Gelfoam. Surgeons may elect to place Silastic or Gelfilm over the promontory to prevent adhesions between the drum and middle ear mucosa. Although the middle ear is shallow in open techniques, there is usually sufficient space to perform an ossiculoplasty.
The Bondy Modified Radical Mastoidectomy
The Bondy procedure (23), first suggested by Körner (5) in 1899, is a variation of the MRM. Therefore, by definition, this is a canal-wall-down procedure. It can be performed through either an endaural or postauricular incision. This operation is used in cases of large attic cholesteatomas in which the middle ear has been spared of disease. An atticotomy is performed first. The entire scutum is removed toexpose the epitympanum, marsupialize the cholesteatoma, and debride its keratin content. The medial wall of the cholesteatoma matrix is left in place over the body of the incus and head of the malleus in the epitympanum. This seals the middle ear space. If the cholesteatoma is seen extending around the ossicles, the surgeon must be prepared to perform a more traditional MRM.
If involvement of the middle ear is in question preoperatively, a high-resolution computed tomography (CT) scan of the temporal bone with axial and coronal views may help determine whether a Bondy procedure is indicated. This operation is reserved for those ears with large primary acquired cholesteatomas in which hearing is preserved and the ossicular chain is free of disease. A Bondy mastoidectomy is a particularly useful technique in cases with cholesteatoma and a labyrinthine fistula, especially in an only hearing ear. After the procedure, keratin can be debrided in the office while leaving the medial matrix of the cholesteatoma intact over the fistula. The surgeon must be vigilant, however, during each office examination. If cholesteatoma appears to extend into the middle ear, this finding should be verified with CT imaging. A traditional MRM would then become necessary.
Meatoplasty and Mastoid Obliteration
The most important factors in avoiding a chronically draining cavity are adequate removal of disease during surgery, designing a properly shaped mastoid cavity, and creating a wide external auditory meatus.
Mastoid Obliteration
Following canal-wall-down mastoidectomy, the patient is left with a cavity. The keratinizing squamous epithelium that lines the mastoid bowl is prone to collecting debris and should be cleaned on a regular basis. Many patients must adhere to lifelong water precautions to minimize risk of infection. Some technical considerations help to limit postoperative complications in a canal-wall-down mastoidectomy (2,24,25,26,27,28,29,30). Wide saucerization of the mastoid bowl allows the surrounding soft tissues to prolapse into and partially obliterate the cavity. Lowering the facial ridge and performing a generous meatoplasty also helps. Avoiding a dependent mastoid tip prevents accumulation of debris in this difficult to clean area. Lowering the bony canal wall and inferior annulus flush with the hypotympanum facilitates in-office access to the dependent areas of the mastoid.
Some surgeons obliterate the mastoidectomy cavity in more formal ways. Originally described by Mosher (27), the Palva flap has been used successfully in obliterating mastoid cavities (2). This flap is a long, laterally based postauricular musculoperiosteal flap that is rotated into cavity at the end of the procedure. Postmortem histologic examination of temporal bones from patients who underwent mastoid
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obliteration with the Palva flap has demonstrated viable muscle, fat, collagen, and richly vascularized tissue years after the procedure. There can be some atrophy, however, over the 5-year period after mastoidectomy. This may result in progressive widening of some cavities (29,31). Other potential flaps that could be used to obliterate the mastoid bowl include an anteriorly based temporalis muscle flap or a temporalis fascia flap based on superficial temporal artery pedicle (the Hong Kong flap) (25,32). Such flaps provide bulk, cover exposed bone, recruit a blood supply, and provide a surface for epithelial migration. Palva (30) has advocated the use of bone pâté and bone chips for obliterating the mastoid defect. It is important to collect the bone pâté from cortical bone, before entering the diseased portions of the mastoid. This pâté is laid into the cavity at the end of the case and flaps rotated over it. All bone pâté must be completely covered by fascia or the Palva flap. Osteoneogenesis then results in further reduction of the size of the mastoid cavity (31) over time.
Grote and Blitterswijk (32) have described reconstructing the posterior canal wall with porous hydroxyapatite. It is packaged as a preformed prosthesis, which can then be covered with a vascularized flap (33,34). Others have used cartilage for canal wall reconstruction. Montandon et al. (24) recommended combining the canal-wall-up procedure with mastoid obliteration using a fat graft as a means of avoiding recurrent disease. They also exteriorize the attic into the ear canal.
Meatoplasty
Enlarging the external auditory meatus is a necessary part of canal-wall-down procedures. It promotes aeration and epithelialization, facilitates effective postoperative care, and makes office debridement of the cavity much easier. An adequate meatoplasty also reduces the depth of the bowl. Several techniques to enlarge the external auditory meatus have been devised. Each involves removing some conchal cartilage and drapes the posterior meatal skin into the mastoid bowl (Fig. 141.11).
An excellent meatoplasty can be performed by connecting superior and inferior Lempert endaural incisions with the postauricular incision. The superior cut is brought out laterally into the tragal incisura while the inferior cut is curved just medial to the antitragus. This creates a laterally based composite flap made of conchal cartilage and meatal skin. Varying amounts of this cartilage can be removed (through the postauricular incision), leaving behind thin conchal skin that drapes into the mastoid bowl. Adequate resection of cartilage and appropriate positioning of the posterior canal skin are vital. The meatus can be maintained open by placing absorbable sutures from the remaining conchal cartilage and perichondrium to the postauricular periosteum. Three sutures are usually placed: one posterosuperiorly, one directly posterior, and the third posteroinferiorly. The sutures are not tied until all three have been properly placed. These tacking sutures prevent postoperative protrusion of the auricle and collapse of the meatus.
This meatoplasty technique can be adapted to individual reconstructive needs. Portmann (35) describes a three-flap technique that maximizes canal epithelium in appropriate cases. The meatus can be enlarged superiorly by only removing cartilage at the base of the helix as it joins the concha. The surgeon should tailor the extent of cartilage removal to the size and shape of the postmastoidectomy cavity.
Endoscopy
Endoscopes often see where the microscope cannot. The surgeon’s view through the operating microscope depends on a clear line of sight. A 1.7- to 2.8-mm, 30-degree rigid telescope, however, can look around a corner to visualize the facial recess, sinus tympani, or epitympanum. It can also be used to assess the depth of retraction pockets and determine the extent of cholesteatomas. Some authors have advocated the use of endoscopes for second-look procedures following intact canal wall tympanomastoidectomies (36,37,38). Rosenberg et al. (37) reported that endoscopic findings correlated well with open surgical exploration in ten out of ten patients. The role of endoscopy will continue to expand in the otologic and neurotologic applications as surgeons become more comfortable with their use and larger studies confirm their efficacy.
Endolymphatic Shunt
In 1927, Guild (39) proposed that endolymph in the inner ear may flow from the cochlea to the endolymphatic sac. It was near this time that Portmann (40) first incised the endolymphatic sac in the treatment of Ménière disease. Interestingly, however, not until a decade later did Hallpike and Cairns (41) demonstrate the histopathology of endolymphatic hydrops in patients with Ménière disease. Since then multiple procedures have been designed to “shunt” endolymph from the endolymphatic sac for the treatment of intractable Ménière disease. House (42) advocated shunting endolymph from the sac to the subarachnoid space by placing a specially designed shunt tube through the medial wall of the endolymphatic sac. Shea (43) described drainage of endolymph from the sac into the mastoid cavity using a Teflon film. Shambaugh (44) believed decompression of the sac without incision yielded the same results. Shunts from the endolymphatic sac into the mastoid have been established using Silastic strips or specially manufactured valves (45,46). Successful control of vertigo is reported in a majority of patients regardless of the technique used, but some have questioned the efficacy of these procedures (47) (see Chapter 156).
Exposure of the endolymphatic sac requires a complete mastoidectomy. The facial nerve is clearly identified and
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traced from the second genu through its vertical segment. The posterior semicircular canal is identified, and the posterior fossa plate between the sigmoid sinus and the posterior semicircular canal is thinned. The inferior crus of the posterior semicircular canal does not extend more than 12 mm inferior to the tip of the incus (48). The sigmoid sinus is followed inferiorly toward the jugular bulb. As the posterior fossa plate is thinned, the endolymphatic sac comes into view just posteroinferior to the posterior semicircular canal. This structure appears as a thickened, white area of dura. The bone overlying the sac must be removed, and its lateral wall is incised (Fig. 141.12). Because the “lumen” of the endolymphatic sac is a labyrinth of small, interconnected lumina, space for the shunt is created by blunt dissection. The surgeon should place a sickle knife or similar instrument into the sac and palpate the operculum. An anterior sigmoid sinus may completely overlie the endolymphatic sac. In such cases, the sinus can be decompressed and retracted posteriorly for visualization of the sac. One should be vigilant for the presence of a high jugular bulb. This does not usually impair access to the sac but its presence limits the amount of space available to the surgeon inferior to the posterior semicircular canal. The patient should be well secured to the bed; decompressing the posterior fossa plate and endolymphatic sac often requires that the patient be rotated maximally toward the surgeon.
Figure 141.11 Meatoplasty following canal-wall-down mastoidectomy. A: Axial view of unoperated temporal bone. SS, sigmoid sinus; Tm, tympanic membrane. B: Axial view of temporal bone after canal-wall-down mastoidectomy.C: Axial view after meatoplasty and partial obliteration of mastoid bowl with muscle-periosteal flap.
Figure 141.12 Transmastoid exposure of endolymphatic sac. LSC, lateral semicircular canal; PSC, posterior semicircular canal.
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Petrous Apicectomy
Infections of the mastoid and middle ear can spread to the anterior and medial segment of the temporal bone known as the petrous apex. Petrous apicitis is classically characterized by deep retroorbital pain, abducens nerve palsy, and otorrhea (Gradenigo syndrome). Cranial nerves V, VI, and VII may become involved (49,50). Surgical access to the petrous apex becomes necessary for drainage of expanding cholesterol granulomas and mucosal cysts, exenteration of infected air cells, removal of cholesteatomas, and biopsy of various mass lesions.
The petrous apex takes the form of a truncated pyramid (Fig. 141.13) divided into an anterior and posterior portion by a coronal plane through the internal auditory canal. Thirty percent of posterior petrous apices and 9% of anterior apices are pneumatized (50). The petrous tip is in close relation to Dorello canal and Meckel cave. Dorello canal, formed by the petrous apex, clivus, and petrosphenoidal (Gruber) ligament, contains the abducens nerve. The trigeminal fossa (Meckel cave), in the floor of the middle cranial fossa, houses the trigeminal (Gasserian) ganglion. Given this anatomy, it is easy to see why diseases here can compromise cranial nerves V and VI.
The classic procedures designed to access the posterior petrous apex include the transmastoid infralabyrinthine approach and the translabyrinthine approach. Procedures used to access the anterior petrous apex include the infracochlear approach, the transotic approach, the middle fossa approach, and an anterior approach through theglenoid fossa (Fig. 141.14). Other procedures including the transcanal anterior approach (51), endoscope-assisted approach (52), and an image-guided approach through the sphenoid sinus (53) have also been described. Sparing the otic capsule surgically is preferred in patients with serviceable hearing.
Fortunately, most lesions in the petrous apex require drainage rather than en bloc resection. An isolated middle cranial fossa approach can be used when the disease involves the anterior petrous apex but spares the middle ear and mastoid. Unfortunately this approach does not allow for dependent drainage. Details regarding the middle fossa approach are beyond the scope of this chapter. In brief, however, the pathology is approached from an extradural, superior direction after creating a temporal craniotomy. The temporal lobe is retracted superiorly. The internal auditory canal is delineated with small diamond burrs as the key surgical landmark. Bone anterior to the internal auditory canal and medial to the carotid artery is removed to access the lesion.
The classic infracochlear approach provides direct surgical access to the petrous apex. A postauricular incision is made and the ear raised forward in the usual manner. A wide superiorly based tympanomeatal flap is elevated using canal incisions in the 10-o’clock and 2-o’clock positions. The flap should be relatively long so as to cover the enlarged tympanic ring created by the procedure. This flap is folded into the anterior-superior quadrant and a canaloplasty is performed lowering both the inferior tympanic ring and the floor of the external auditory canal. Theinfracochlear air cell tract must then be identified. It is initially bordered by the basal turn of the cochlea superiorly, the vertical segment of the internal carotid artery anteriorly, and the jugular bulb inferiorly. A 1- or 2-mm diamond burr and
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suction irrigation are used to open the air cells of this tract. Once the biopsy or drainage procedure is complete, a silastic stent can be placed into the pathway to facilitate aeration. The tympanomeatal flap is returned to its anatomic position, and the ear is closed in the usual manner. A high-riding jugular may prohibit use of this approach.
Figure 141.13 A: Superior view of base of skull. B: The petrous apex with the relative location of the internal auditory canal and labyrinth. C: Petrous apex divided into the anterior and posterior portions. APA, anterior petrous apex; PPA, posterior petrous apex.
The transmastoid, infralabyrinthine approach to the petrous apex necessitates a complete mastoidectomy and precise delineation of the facial nerve. The canal wall may be maintained in patients with adequate mastoid development and pneumatization. The infralabyrinthine air cell tract is located inferior to the posterior semicircular canal, superior to the jugular bulb, and medial to the facial nerve. This tract is opened in an anterior and medial direction. The route passes inferior to the internal auditory canal and through the cochlear aqueduct, which must be plugged to prevent a postoperative cerebrospinal fluid (CSF) leak. The lesion in question should be exteriorized or biopsied, and
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a silastic stent placed. Adequate review of preoperative high-resolution CT scans will determine whether this tract is present and of reasonable caliber for access.
Figure 141.14 A: Access to the posterior apex air cells. B: Access to the petrous apex via the infra-labyrinthine air cell tract. C: Anterior approach to the anterior petrous apex through the glenoid fossa. D: Axial view of the temporal bone demonstrating the approaches to the petrous apex. VII, seventh cranial nerve; VIII, eighth cranial nerve; APA, anterior petrous apex; C, carotid artery; CO, cochlea; ET, eustachian tube; PPA, posterior petrous apex. (From Chole RA. Petrous apicitis: surgical anatomy. Ann Otol Rhinol Laryngol 1985;94:251, with permission.)
Patients with large lesions and no serviceable preoperative hearing are candidates for the transotic approach. This route provides superior access for complete removal of mass lesions such as cholesteatomas. The procedure begins with a radical mastoidectomy and removal of the stapes suprastructure. The semicircular canals are drilled away as is the cochlea. Great care is taken to delineate and protect the facial nerve (superior and posterior), petrous carotid (anterior), jugular bulb (inferior), and internal auditory canal. The surgeon dissects in an anterior and medial direction. Should a patent cochlear aqueduct be encountered, it must be plugged with bone wax at the end of the case. After removing the mass in question, most surgeons choose to obliterate the cavity with fat, plug the eustachian tube, and close off the external auditory canal.
Gerek and colleagues (51) describe a transcanal approach for drainage of limited lesions in the anterior petrous apex. Using cadaver dissections, they suggest elevation of a wide, superiorly based tympanomeatal flap followed by a generous anterior and inferior canalplasty. The vertical segment of the petrous carotid is exposed and traced for 5 to 10 mm. The cortical bone anterior to the cochlea, between it and the internal carotid artery, is then drilled. These authors report that an air cell tract to the anterior petrous apex is present in this location with mean anterior-posterior diameter, height, and length of 4.7, 3.2, and 14.7 mm, respectively.
If greater exposure of the anterior apex is required, the complete apicectomy of Ramadier and Lempert may be performed (54,55,56). The glenoid fossa must be exposed and the mandibular condyle can either be removed or displaced anteriorly. This provides access to the medial wall of the glenoid fossa. In the classically described procedure, the anterior external auditory canal wall is removed. However, it can be preserved in most cases. The position of the petrous carotid must be kept in mind as the medial wall of the glenoid fossa is removed using diamond burrs and suction-irrigation. All bone between the carotid artery and the dura of the middle cranial fossa is removed (Fig. 141.14C). Complete exenteration of the anterior petrous apex is impossible without performing a labyrinthectomy, but, in most cases, drainage of infected cells is sufficient to reverse the suppurative process (Fig. 141.14D).
Complications and Emergencies (Table 141.3)
Facial Nerve Injury
The facial nerve is at risk in its labyrinthine, tympanic, and mastoid segments during otologic surgery. The nerve not only takes a tortuous, sometimes-anomalous course through the temporal bone, but its canal may also be dehiscent. Heat generated by a diamond burr can injure the nerve without direct mechanical trauma. Constant suction-irrigation helps dissipate thermal energy and prevent this complication. Landmarks such as the antrum, horizontal semicircular canal, short process of the incus, fossa incudus, cochleariform process, oval window, pyramidal process, chorda tympani, and digastric ridge help to locate the nerve. However, such landmarks may be absent or altered during procedures for congenital atresia or cases requiring revision surgery. Intraoperative facial nerve monitoring may be helpful in reducing the risk of iatrogenic trauma.
TABLE 141.3 COMPLICATIONS: MASTOID SURGERY
Perioperative complications
   Facial nerve injury
   Sensorineural hearing loss
   Postoperative infection
   Dysgeusia
   Brain herniation
   Cerebrospinal fluid leakage
   Bleeding
Delayed complications
   Posterior canal breakdown
   Perichondritis
   Blue-domed cyst
   Mucosalization of mastoid bowl
   Stenosis of external canal
If the facial nerve is traumatized during surgery, the extent of injury should be assessed both by direct observation and electrical testing. The region of the suspected injury should be examined by decompressing the nerve 5 to 10 mm proximal and distal to the site of injury. It should be exposed in a 180-degree fashion. If facial muscle contraction can be elicited by stimulation with 0.5 mA or less proximal to the injured area, further treatment is unnecessary. Systemic corticosteroids may be helpful in the postoperative period to minimize swelling. If facial movement can be elicited by stimulation of the nerve distally but not proximal to the injury, the extent of nerve disruption determines the next course of action. If only a few fibers are damaged, they may simply be returned to their anatomic position. Significant disruption of the nerve, however, requires either direct reanastomosis or cable grafting. When greater than 50% of the facial nerve was disrupted, Green and colleagues obtained a House-Brackmann Grade III recovery using direct reanastomosis and Grade IV with cable grafting (57). Direct repair may require facial nerve rerouting, which itself may compromise nerve function.
Unexpected facial paralysis noted postoperatively requires prompt attention. Weakness without frank paralysis has a good prognosis and can be treated with a tapering course of steroids. However, complete facial paralysis in patients where the nerve was never formally identified presents a diagnostic dilemma. Local anesthetics administered
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preoperatively may be responsible for immediate postoperative facial palsy. Therefore, surgical exploration should be deferred for a few hours and the patient reassessed. If complete paralysis persists, early exploration is indicated. The nerve must be clearly identified, and, if traumatized, the surgeon should decompress it or perform the necessary repair.
Hearing Loss
Iatrogenic hearing loss may be conductive or sensorineural. Undetected disruptions of the tympanic membrane or ossicular chain may cause a conductive hearing loss. Sensorineural hearing loss can result from a variety of causes. Acoustic trauma from a loud drill or suction squeal near the footplate may cause hearing loss. Transmission of high frequency mechanical energy from contact between the drill and the ossicular chain also causes sensorineural hearing loss. If such contact is unavoidable, the surgeon should first disarticulate the incudostapedial joint. Inadvertent entry into the inner ear (semicircular canal, oval or round window, cochlea, etc.) and loss of perilymph/endolymph may result in hearing loss. The surgeon must be especially cautious when operating on an only hearing ear (58). If faced with cholesteatoma matrix overlying the stapes footplate or a horizontal semicircular canal fistula, removing this matrix may result in a sensorineural hearing loss. The options here include completely removing the cholesteatoma, exteriorizing the matrix, or simply leaving a small part of cholesteatoma behind. The surgeon may elect the latter option and perform a second operation in 6 to 12 months. At that time, the residual cholesteatoma matrix (now a small pearl) can be removed. This second procedure is usually safer because the field is no longer infected and visualization much improved.
Vestibular Injury
Injury to the labyrinth during tympanomastoid surgery can result from direct trauma or from postoperative infection. Ears affected by serous labyrinthitis often recover function over time and may benefit initially from steroid therapy. Suppurative labyrinthitis, however, usually destroys vestibular function. Complete unilateral vestibulopathy usually results in acute vertigo. This resolves over the next few days to weeks as central compensation occurs. Some patients are left with mild disequilibrium that improves slowly with vestibular rehabilitation. Chronic disequilibrium may occur in those patients who do not undergo successful central compensation. Some patients may also experience delayed benign positional vertigo. These patients may be treated with repositioning maneuvers and vestibular rehabilitation.
Infection
Postoperative infection continues to pose a threat to successful outcomes in otologic surgery. Immediate concerns include dehiscence of the postauricular incision, failure of the tympanoplasty grafts, and necrosis of the external auditory canal skin flaps. Perichondritis requires debridement of necrotic cartilage and administration of parenteral antibiotics. Other potential complications include suppurative labyrinthitis, facial nerve palsy, epidural or subdural abscess, meningitis, sigmoid sinus thrombosis, otitic hydrocephalus, and brain abscess. If an ear is grossly infected preoperatively, antibiotics may be administered based on cultures and sensitivity data. Intraoperative irrigation with antibiotic solutions may also be of benefit. For most otologic procedures, however, preoperative prophylactic antibiotic therapy is not indicated. In a recent review by Verschuur and colleagues, they concluded that there was no role for the use of prophylactic antibiotics in clean and clean-contaminated otologic procedures (59).
Dysgeusia
Dysgeusia resulting from injury to the chorda tympani nerve may be quite distressing to some patients. Symptoms such as a metallic taste in the mouth usually improve with time, but patients must be warned that these taste alterations may persist. This may be of particular concern for those needing a keen sense of taste or flavor in their professions. Traumatized chorda tympani nerves tend to result in more prolonged dysgeusia than cutting the nerve.
Cerebrospinal Fluid Leakageand Encephalocele
The terms meningocele, encephalocele, and meningoencephalocele refer to herniation of meninges, brain matter, or both outside their normal confines. In the course of thinning the tegmen tympani and tegmen mastoideum, small areas of dura may become exposed. This is generally of little consequence. However, if larger areas of dura are exposed or lacerated, CSF, meninges, and brain tissue may enter into the mastoid cavity. Elderly patients are at particular risk because the dura tends to thin with advancing age.
Encephaloceles usually present with CSF otorrhea, CSF rhinorrhea, a persistent clear effusion behind an intact tympanic membrane, hearing loss due to mass effect (fluid and brain matter), or infections such as meningitis and encephalitis. A CSF leak can occur, however, without herniation of meninges or brain matter. High-resolution CT scans with axial and coronal views help define bony defects in the tegmen or posterior fossa plate, and magnetic resonance imaging (MRI), with its excellent soft tissue resolution, distinguishes brain from fluid, cholesteatoma, or cholesterol granuloma. MRI is also useful in evaluating the integrity of the dura. β2-transferrin assays, capable of detecting minute quantities of CSF, help with thediagnosis.
Conservative options for managing CSF leaks include bed rest, stool softeners, and placement of a lumbar drain
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for controlled CSF removal. When such measures fail or if the patient becomes infected, surgical options are necessary. Repairing an encephalocele requires resection of devitalized tissue followed by reconstruction of the defect. If the damage is recognized during the initial procedure, the defect can be repaired at that time. Dura is elevated in a circumferential manner around the defect and a fascia graft placed intracranially between the dura and bone. Other materials available to the surgeon in place of fascia include pericranium, Alloderm, homograft pericardium, or DuraGen. More fascia, cartilage, bone, or commercially available alloplastic materials can then be placed against the defect from within the mastoid. If the CSF leak or encephalocele is recognized postoperatively, the precise location of the defect and the patient’s hearing status dictate the surgical approach. An audiogram and imaging should be obtained. Options include transmastoid, middle fossa, or combination techniques. For small defects, a mini middle fossa craniotomy can be used. The temporal lobe is elevated and a sheet of temporalis fascia is placed below the dural defect. The window of bone harvested in the craniotomy is thinned and inserted between the fascia and the floor of the middle cranial fossa. Approaching the dura carefully using diamond burrs rather than cutting burrs helps to prevent these injuries.
Bleeding/Air Embolism
Most bleeding from the sigmoid sinus or jugular bulb can be controlled easily using Gelfoam or Surgicel pledgets covered by a small cottonoid. However, a significant laceration places the patient at risk for secondary complications such as air embolism or thrombosis of the sigmoid sinus. Once the bleeding is controlled, the potential for air embolism must be entertained. An air bubble in the venous system that becomes trapped within the right ventricle can result in cardiopulmonary arrest. The early signs of air embolism include increased end-expiratory carbon dioxide, hypotension, and abnormal cardiac sounds. The surgical field should be flooded with saline immediately and the patient should be placed in the Trendelenburg (head-down) position to minimize further ingress of air into the vascular system. Placement in the left lateral position can help to reposition the air bubble into the right atrium or vena cava. If cardiovascular compromise is still present after these maneuvers, the air must be aspirated from the vena cava using a central venous catheter.
Injury to the carotid artery during tympanomastoid surgery requires immediate hemostasis by direct occlusion. Once the bleeding is temporarily controlled, options include direct repair of the vessel, ligation proximally in the neck with occlusion distally, angiography with embolization or placement of coils, and angiography with stenting. Even with these interventions, the patient remains at risk for stroke.
Delayed Complications
Other complications of mastoid surgery include delayed posterior external ear canal wall breakdown, perichondritis, cholesterol granulomas, mucosalization of the mastoid bowl, and external auditory canal stenosis.
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