Vertigo And Perforated Tympanic Membrane

REVISION MASTOIDECTOMY

John F. Kveton

Persistent or recurrent drainage from the ear after canal-wall-up (CWU) surgery may be related to surgical technique or patient disease. Drainage indicates the presence of chronic otitis media, but the exact cause of the chronic otitis media must be determined. Factors that may help determine the cause of recurrent aural drainage include the timing of the appearance of the drainage in relation to the original surgery; the frequency of the drainage; the pathology in the original surgery; the status of the tympanic membrane; the development of symptoms such as hearing loss, vertigo, or facial palsy; and other associated patient disease. The development of aural drainage immediately after surgery suggests failure to exenterate all active disease at the time of the original mastoidectomy. This is usually related to poor surgical technique. Recurrent drainage weeks to months after the initial procedure may also be due to poor technique, but may also be secondary to residual cholesteatoma, or may be due to organisms resistant to standard therapies. Intermittent drainage, rather than constant drainage, suggests the presence of cholesteatoma or eustachian tube dysfunction related to allergy. Recurrent drainage after CWU surgery for cholesteatoma indicates recurrent cholesteatoma until proven otherwise.

The presence of drainage with tympanic membrane perforation and granulation tissue may indicate poor technique with residual disease, inadequate eustachian tube function, or cholestea-toma. Retraction of the tympanic membrane with drainage indicates poor eustachian tube function and possible development of cholesteatoma. The development of hearing loss, vertigo, or facial palsy in the presence of an intact tympanic membrane indicates cholesteatoma, whereas the presence of these symptoms with a perforated tympanic membrane may also be due to activation of significant bacterial disease. The appearance of aural drainage in a seasonal timeframe indicates an allergic factor causing poor eustachian tube function. Aural drainage during exacerbation of connective tissue disorders is related to the proliferation of granulo-matous tissue within the middle ear and mastoid, while poor control of serum glucose in diabetes will result in the worsening of any existing chronic infection.

Evaluation

Evaluation of the draining ear should begin with inspection of the auricle and the mastoid region. Postauricular swelling is a sign of acute mastoiditis, whereas tenderness over the mastoid region suggests a subacute process. Swelling of the external auditory canal indicates that the chronic otitis media has produced otitis externa as well. This situation is usually found in long-standing chronic disease with extensive granulation tissue formation in the middle ear or in immunocompromised patients. The status of the tympanic membrane can provide clues as to the cause of failure of the previous procedure and so guide in future surgical decision making. A total tympanic membrane perforation with granulation tissue filling the middle ear suggests widespread disease throughout the temporal bone. An anterior, dry perforation may indicate poor eustachian tube function, but more likely reflects inadequate surgical technique. A retracted tympanic membrane, with or without an attic retraction, reveals eustachian tube dysfunction. In this situation, especially after a firststage intact-canal-wall procedure for cholesteatoma, it is impossible to determine whether residual or recurrent cholesteatoma is present prior to surgery.

Audiometric evaluation is mandatory prior to revision mastoidectomy. Conductive hearing loss should be expected in these cases. Asymmetric sensorineural hearing loss should raise concern. Sensorineural hearing loss indicates that inner ear damage may have occurred at the previous procedure, but such hearing loss is also suggestive of fistulization of the inner ear caused by aggressive disease. Sensorineural hearing loss should therefore alert the surgeon to proceed cautiously around the labyrinth and cochlea during surgery. The degree of conductive hearing loss can also be helpful in surgical planning and counseling. Mild conductive hearing loss suggests that the ossicular chain is intact and that removal of disease and repair of the perforation should restore hearing to normal. A hearing loss greater than 40 dB usually indicates ossicular chain disruption or fixation. The ultimate hearing result in such cases is always more variable.

In addition to audiometric testing, imaging of the temporal bone should be performed prior to most revision mastoid procedures. This is usually not necessary in planned second-stage procedures for cholesteatoma. Noncontrast high-resolution computed tomography (CT) scan of the temporal bone is the imaging procedure of choice. Plain films of the mastoid should be performed only when CT scans are not available. Magnetic resonance imaging (MRI) should be used as a secondary imaging modality. It is indicated when there is concern of an intracranial complication of mastoiditis such as meningoence-phalocele, intracranial abscess or inflammation, or venous sinus thrombosis. CT scans aid in diagnosis and surgical planning. Although the appearance of soft tissue within the mastoid defect is not uncommon, complete opacification of the operative mas-toid defect, especially with obstruction of the attic, is evidence of active disease. Soft tissue involvement of residual air cells suggests persistent disease. Especially in the attic region, these air cells may be responsible for chronic ear drainage. Erosive changes in the temporal bone are important to note, because erosion suggests cholesteatoma in the vast majority of cases, and rarely, neoplasm. In particular, the otic capsule should be examined for fistula.

Tegmen defects should be identified, both for their diagnostic significance and surgical planning. The absence of the tegmen at the cortex must be recognized prior to revision surgery to avoid dural injury during initial exposure of the mastoid defect. Tegmen defects deep within the temporal bone indicate progressive disease if such defects were not present after the initial procedure. The fallopian canal should be examined to deter mine possible facial nerve exposure. Although it is difficult to identify dehiscence precisely, especially of the horizontal segment, the proximity of soft tissue or bone erosion near the fallopian canal should alert the surgeon to the possibility of facial nerve exposure during the revision procedure. The status of the ossicular chain may be implied by identification of the structures on CT scan, but the presence of soft tissue surrounding the ossicles in most cases produces averaging artifact that makes positive identification of ossicular continuity impossible.

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