Giant cholesterol cysts of the petrous apex: radiologic features.

Four cysts are described that expanded and destroyed the bone of the petrous apex. All patients with these cysts had a sensorineural hearing loss. Mild symptoms referable to cranial nerves VI, VII, IX, X, XI, and XII were seen also. The cysts range in size from 1.5 X 1.5 X 3 cm to 5 X 5 X 6 cm. Grossly and histologically, they were distinct from any lesions seen previously. The lesions were large and contained glistening brown, watery fluid filled with cholesterol crystals. The cyst wall was predominantly fibrous tissue without an epithelium. Minimal chronic inflammatory change and granuloma formation were present within and just outside the cyst wall. These cysts have been described as mastoid cysts, epidermoids, mucoceles, and cholesterol granulomas; until now, they have not been recognized as a single distinct entity. A name emphasizing the pathologic characteristic of the lesion, giant cholesterol cyst, has been suggested. Distinguishing them from other petrous apex lesions preoperatively is difficult, but if the cystic nature of the lesion can be recognized or at least anticipated, more conservative surgery, such as simple drainage versus a more radical procedure, may be possible.

Retrolabyrinthine vestibular nerve section: analysis of results.

The retrolabyrinthine section of the vestibular nerve is an effective procedure for the ablation of unilateral vestibular function while preserving hearing. Although this procedure has been most frequently used for the control of unilateral Meniere's disease, it may also be effective in the control of unilateral vestibular dysfunction of other etiologies. A 2-year experience with the indications for and the surgical results in a series of patients who underwent this procedure is presented. Brief case histories of a variety of etiologies of unilateral vestibular dysfunction are discussed.

Surgical management of Meniere's disease with endolymphatic sac decompression by wide bony decompression of the posterior fossa dura: technique and results.

The results of wide bony decompression of the posterior fossa in 49 consecutive individuals with idiopathic unilateral Meniere's disease are reported. These results are similar to many previously published series, 71% of individuals are free of vertigo and 86% have unchanged or improved hearing. Utilizing the classification proposed by the American Academy of Ophthalmology and Otolaryngology, 73% fell into Class A, B, or C with relief of vertigo. These results together with the low complication rate encourages us to consider surgery at an earlier date, hoping to stabilize hearing at a more useful level and to relieve vertigo.

Retrolabyrinthine vestibular nerve section: efficacy in disorders other than Menière's disease.

The retrolabyrinthine vestibular nerve section has evolved as an effective treatment for intractable vertigo of peripheral vestibular origin when hearing preservation is desired. This report studies the efficacy of retrolabyrinthine vestibular nerve section for control of vertigo due to causes other than Meniere's disease. This report details our experience with 42 patients with a wide variety of diagnoses. The reduced success rate of retrolabyrinthine vestibular nerve section in these patients is difficult to evaluate, as very few patients have been analyzed with respect to their specific diagnoses. Of patients who underwent retrolabyrinthine vestibular nerve section for control of vertigo, 23 patients had uncompensated vestibular neuritis and 19 others had a wide range of other diagnoses. For patients with uncompensated vestibular neuritis (n = 23), the physician record noted that 39% of patients were cured and 30% improved. This compares to our series of patients with Meniere's disease (n = 48), where 94% were cured and 2% improved. The true vestibular abnormality may be less reliably identified in patients with uncompensated vestibular neuritis, contributing to the less effective results. Since the development of a vestibular rehabilitation program, retrolabyrinthine vestibular nerve section for uncompensated vestibular neuritis has been all but abandoned. Retrolabyrinthine vestibular nerve section appears to achieve a high cure rate in patients with sensorineural hearing loss associated with their vestibular abnormalities. While retrolabyrinthine vestibular nerve section is helpful for control of vertigo in some diagnoses, a substantial incidence of persistent postoperative dysequilibrium was noted.

Anatomic basis for labyrinthine preservation during posterior fossa acoustic tumor surgery.

Earlier diagnosis of acoustic tumors promises to increase our opportunity to identify patients with serviceable hearing. Critical to a posterior fossa transmeatal approach for acoustic tumor resection is preservation of the underlying labyrinth. Although the labyrinth has been recognized as a limiting factor in exposure of tumor in the internal auditory canal, few reports have detailed the microscopic surgical anatomy posterior to the internal auditory canal. An anatomic study was undertaken to determine consistent relationships between critical structures within the temporal bone relevant to hearing preservation surgery. The results of this study indicate that, whereas topographic landmarks are helpful for orientation, the more consistent relationship of the labyrinth to the vestibular aqueduct and singular canal allows a more accurate localization of the underlying labyrinth. Although the vestibule frequently prevents direct visualization of the transverse crest, a dissection based upon the microsurgical anatomy will maximize visualization of the lateral fundus while preserving the integrity of the labyrinth.

The giant cholesterol cyst of the petrous apex: a distinct clinical entity.

The giant cholesterol cyst (GCC) of the petrous apex may now be considered a distinct clinical entity and should be considered in the differential diagnosis of lesions of the midcranial skull base. This benign cystic lesion of the petrous apex gradually enlarges and may produce progressive bone erosion and serial neurologic deficits of the cranial nerves within the temporal bone and jugular foramen. We report here five instances of this lesion (3 patients with unilateral and 1 patient with bilateral petrous apex lesions) and describe the natural history, diagnostic evaluation, pathology, and surgical management.

Intraoperative facial nerve monitoring: a comparison of stimulating electrodes.

Preservation of the facial nerve during acoustic neuroma resection may be enhanced by the use of intraoperative electrical stimulation. Although stimulation of the extratemporal facial nerve is an effective and established procedure, anatomic differences of the intradural facial nerve and its microenvironment demand more exacting stimulus protocols. The absence of epineurium may make the intradural nerve more susceptible to mechanical or electrical trauma while intermittent pooling of cerebrospinal fluid (CSF) at the cerebellopontine angle may shunt current away from nerve. Four stimulus configurations were examined under varying conditions simulating CSF pooling. The results indicated that: 1. insulation of stimulating electrodes prevents CSF current shunting and allows utilization of a constant current source, and 2. monopolar and bipolar configurations demonstrate significantly different electrical characteristics which may be employed selectively based upon specific clinical goals.

Hearing preservation following suboccipital removal of acoustic neuromas.

Advances in the diagnosis and intraoperative management of acoustic neuromas have greatly reduced the incidence of neurologic deficits following their removal. Ninety-three patients underwent acoustic tumor removal during a 41/2-year period, and hearing preservation was attempted in 20 cases. Hearing was preserved in 65% of the entire series, and excellent results were obtained in tumors less than 1.5 cm. No patient with a tumor greater than 1.5 cm had serviceable hearing preserved when total tumor removal was performed. Two patients, one with neurofibromatosis and one with an acoustic neuroma in an only-hearing ear, had planned partial tumor removal with preservation of hearing. Preoperative auditory brainstem response results were not predictive of postoperative hearing preservation. Intraoperative auditory brainstem response monitoring demonstrated that loss of wave V consistently correlated with loss of hearing postoperatively, whereas persistence of wave V (with a latency prolongation not exceeding 3.00 ms) was predictive of successful hearing preservation regardless of latency increases.

Normal auditory brainstem response in patients with acoustic neuroma.

Auditory brainstem response testing has been a major breakthrough in audiologic screening for acoustic neuroma because of its high degree of sensitivity. Although it is not uncommon for other cerebellopontine angle masses to present with normal ABR findings, reports of eighth nerve tumors with false-negative auditory brainstem response tests are quite rare. A series of 120 acoustic neuromas resected at the University of Michigan was reviewed and revealed two such patients. These two patients presented with asymmetric sensorineural hearing loss and unilateral tinnitus and were found to have completely normal auditory brainstem response. The diagnosis of acoustic neuroma would have been delayed if a comprehensive evaluation had not been pursued.

Bioactive glass ceramic in ossicular reconstruction: a preliminary report.

Current techniques for ossicular reconstruction include ossicular autografts and homografts, and plastic and ceramic prostheses. Experimental testing of ceramic materials has led to the development of a nonporous, bioactive form of glass ceramic (Ceravital) for tympanoplastic reconstruction. To determine the clinical usefulness of these implants, Ceravital ossicular reconstructions were evaluated in 37 patients treated at the University of Michigan Medical Center during an 18-month period. Thirty-two patients (86%) with chronic ear disease underwent Ceravital ossicular reconstruction with tympanoplasty with or without mastoidectomy. Five other patients (14%) underwent ossicular reconstruction--2 for congenital anomalies, 2 for temporal bone trauma, and 1 patient for glomus tympanicum removal. Patient follow-up ranged from 2.2 to 3.8 years, with a mean follow-up period of 2.9 years. Prosthesis extrusion occurred in one case (3%). Mean preoperative and postoperative (2-year) pure tone air-bone gaps were 41.6 dB and 21.3 dB, respectively. Hearing was improved in 35 of 37 patients (95%). Postoperative pure tone air-bone gap was closed to 20 dB or less in 23 patients (62%). Hearing gains were greater with partial rather than total reconstructions (p = 0.14) and significantly greater with intact canal wall rather than canal wall down tympanoplasties (p less than 0.05). Initial results obtained with the Ceravital ossicular prosthesis compare favorably with those obtained using other methods of alloplastic reconstruction. These preliminary data suggest that Ceravital is an effective alternative prosthetic material for ossicular reconstruction.

Auditory performance of children with cochlear ossification and partial implant insertion.

The management of the profoundly deaf child with a cochlear implant poses a special challenge, particularly when total ossification of the cochlea is present. In this setting, insertion of an electrode array into a child's cochlea is often difficult. Our experience supports the feasibility of partial insertion of a multichannel implant into the basal turn of an ossified cochlea. Five children with ossified cochleae who had undergone partial implantation of a multichannel electrode were compared with the performance of matched controls who had full insertion of multichannel implants. No dramatic differences were detected during a 6- to 18-month follow-up period on selected test measures. These preliminary results suggest that active electrode number may exert a limited effect on performance with a cochlear implant. Drilling out the basal turn of an ossified cochlea in conjunction with partial insertion of a multichannel implant appears to be an acceptable surgical and rehabilitational alternative for placement of a cochlear implant prosthesis in children with complete cochlear ossification.

Total en bloc resection of the temporal bone and carotid artery for malignant tumors of the ear and temporal bone.

A technique for single stage total en bloc resection of the temporal bone and intratemporal carotid artery with immediate reconstruction has been described. This formidable procedure requires the collaborative efforts of neurotologic skull base surgeons, neurosurgeons, and head and neck surgeons. Two patients have undergone this procedure; one with squamous cell carcinoma and one with extensive basal cell carcinoma. The quality of life following this procedure is adequate and the cosmetic deformity can be minimized. Longer follow-up is necessary to determine the value and overall impact of this approach to cancer of the temporal bone on disease free interval and patient survival. Further experience with the technical aspects of this procedure should reduce the operating time, blood loss, and resultant morbidity.

Local control of auricular, periauricular, and external canal cutaneous malignancies with Mohs surgery.

Three hundred ninety-seven patients with 407 cutaneous malignancies of the auricle, periauricular region, and cartilaginous external ear canal were reviewed. Tumors were most commonly located in the preauricular and postauricular regions, followed by the helix, concha, antihelix, and ear canal. All lesions were excised with Mohs microscopic control of margins. For lesions requiring lateral temporal bone resection, an adaptation of fresh-tissue microscopic control was used to analyze deep and anterior margins suspected of harboring residual tumor. Two-year minimum follow-up of 229 patients with periauricular and auricular tumors (N = 231 tumors) and 14 patients with cartilaginous ear canal tumors (N = 14 tumors) revealed recurrence rates of 6.9% and 14.3%, respectively. Recurrences were most common in cases of large tumors (greater than 2.5 cm), basal cell carcinomas with morphea elements, and multiply recurrent lesions. We conclude that Mohs surgery is comparatively effective, though not uniformly curative, and can be adapted to supplement excision of large tumors in these regions.

Use of bacitracin for neurotologic surgery.

Wound infection, cerebrospinal fluid leak, and meningitis are serious potential complications of neurotologic procedures that transgress the posterior cranial fossa dura. A study of 236 patients was made to determine the effect of perioperative intravenous antibiotics and topical bacitracin irrigation on the incidence of these complications. Of the 236 patients, 170 (72%) underwent translabyrinthine resection of acoustic tumors, while 66 (28%) underwent retrolabyrinthine vestibular nerve section. Patients were divided into four groups: those who received no antibiotics, those who received perioperative intravenous antibiotics only, those who received topical bacitracin irrigation only, and those who received a combination of perioperative intravenous antibiotics and topical bacitracin irrigation. There were no untoward effects of either perioperative intravenous antibiotics or topical bacitracin. The results indicate that bacitracin irrigation reduced the incidence of wound infection from 9% to 2% (p less than 0.05); of cerebrospinal fluid leak from 12% to 5% (p less than 0.04); and of all targeted complications combined from 22% to 9% (p less than 0.006). Furthermore, the topical bacitracin irrigation only group showed a statistically significant reduction in wound infections compared to the perioperative intravenous antibiotic only group (p less than 0.02). The incidence of meningitis was statistically unaffected by any of our treatment protocols.

Electrically evoked middle-latency auditory potentials in cochlear implant candidates.

Electric middle-latency auditory evoked responses (EMLRs) to transtympanic promontory stimulation were obtained from 19 of 22 ears of profoundly hearing-impaired patients evaluated for cochlear implant candidacy. The EMLRs were characterized by positive polarity peaks with latencies ranging from 20 to 30 ms, with the majority of responses exhibiting peaks in the range of 26 to 30 ms. Generally, the configuration of the EMLRs closely resembled the configuration of acoustic MLRs. While in most cases, behavioral thresholds to identical promontory stimulation were slightly lower, EMLR thresholds closely approximated behavioral electrical promontory thresholds. The EMLR thresholds correlated positively with implanted thresholds and exhibited a negative correlation with implanted dynamic current ranges.

Hearing recovery following suboccipital excision of acoustic neuroma.

Improvement of hearing after excision of an acoustic neuroma has been observed infrequently. We present a case of dramatic recovery of hearing in a patient with a 1-cm acoustic neuroma whose pure-tone thresholds and speech discrimination had profoundly deteriorated while she awaited surgical therapy. Postoperatively, her hearing in the affected ear is equal to that in her other ear, and her speech discrimination exceeds that of her best preoperative audiogram. Issues related to hearing preservation and improvement after acoustic tumor surgery are discussed.

Spontaneous encephalocele of the temporal bone.

Postsurgical and posttraumatic encephaloceles of the tegmen tympani and tegmen mastoideum are well-recognized occurrences. Less frequently recognized, however, is the spontaneous occurrence of an encephalocele associated with cerebrospinal fluid otorrhea or rhinorrhea. This cerebral herniation into the middle ear and the mastoid cavity in adults is associated with a loss of both bony and dural support, and surgical management must deal with both the cerebrospinal fluid leak and herniation of the brain.

Magnetic resonance imaging of temporal bone and cerebellopontine angle lesions.

Lesions of the temporal bone and cerebellopontine angle present a diagnostic challenge because of the complex anatomy, multiplicity of lesions, and difficulty in imaging the dense bone of this area. Magnetic resonance imaging, a new, nonionizing imaging modality, dependent on monitoring a radiofrequency signal emitted by excited nuclei in an external magnetic field, has shown promise in imaging of the temporal bone and posterior fossa.

Tinnitus suppression following cochlear implantation. A multifactorial investigation.

The effects of cochlear implant on loudness, annoyance, daily duration, location, and residual inhibition of tinnitus were evaluated by a closed-ended, quantifiable questionnaire in 33 postlingually deafened patients who had received implants at the University of Michigan, Ann Arbor, between 1986 and 1990. Preoperative tinnitus was present in 85% of patients. A statistical comparison of preoperative vs postoperative loudness and annoyance indicated a significant reduction in both of these complaints postoperatively. Loudness and annoyance were significantly correlated, both preoperatively and postoperatively. Fifteen patients (54%) with preoperative tinnitus demonstrated a loudness decrease of 30% or more; 43% demonstrated an annoyance decrease of 30% or more; and 48% demonstrated a decrease of 30% or more in daily tinnitus duration. Patients who experienced a loudness or annoyance decrease of 30% or more after implantation demonstrated significantly higher preoperative levels of these complaints, suggesting that degree of tinnitus reduction after implantation may be related to preoperative loudness and annoyance levels. Contralateral tinnitus suppression was reported by 42% of patients. Residual inhibition ranging from 60 seconds to several hours was reported by 50% of patients, predominantly in the ear with the implant. Age, gender, cause of hearing loss, duration of tinnitus, cochlear implant usage, and time after implantation were not predictive of tinnitus suppression. Overall, the majority of the patients (74%) thought that their cochlear implant was helpful in tinnitus suppression, especially in the ear with the implant. Contralateral residual inhibition and tinnitus suppression suggest a central mechanism contributing to these phenomena.

Facial electroneurography: clinical and experimental investigations.

Facial electroneurography (ENoG) appears to be a reliable prognostic test for intratemporal facial nerve paralysis. ENoG is objective and allows a permanent record to be maintained. Nonetheless, occasional inconsistencies in clinical correlation may diminish the utility of ENoG. A qualitative study was undertaken to identify the possible reasons for the inaccuracy of ENoG in some patients. Four clinical groups and one experimental group were studied: (1) normal subjects, (2) patients with acute facial palsy, (3) patients with progressive facial palsy, (4) patients with temporal bone tumors and normal facial function, and (5) animals in which one facial nerve was crushed and repaired. The reliability of ENoG is dependent on careful interpretation of data obtained by optimal electrode placement and stimulus duration.