Donald B. Kamerer

Acoustic Neuromas: Results of Current Surgical Management

OBJECTIVE In this article, we review the surgical outcomes of 179 patients with acoustic neuromas. METHODS Most of the tumors (84%) were operated on using a retrosigmoid, transmeatal approach. A transpetrosal, retrosigmoid approach was used in 10% of the patients, most of whom had large tumors. The translabyrinthine (4%) and transmastoid, transpetrosal, partial labyrinthectomy approaches (2%) were used selectively. The operative approaches are discussed. Tumors were categorized according to their cerebellopontine angle dimensions as small (< 2 cm), medium (2.0-3.9 cm), and large (> or = 4 cm). RESULTS House-Brackmann evaluation of postoperative facial nerve function revealed excellent results (Grade I or II) in 96% of small tumors, 74% of medium tumors, and 38% of large tumors. A fair postoperative function (Grade III or IV) was achieved in 4% of small tumors, 26% of medium tumors, and 58% of large tumors. Functional hearing preservation, defined as Gardner-Robertson Class I or II, was achieved in 48% of small tumors and 25% of medium tumors. Hearing was not preserved in any of the three patients with large tumors in whom hearing preservation was attempted. Treatment complications consisted mainly of cerebrospinal fluid leakage (15% of the patients). The majority of the patients who experienced cerebrospinal fluid leakage were treated successfully with lumbar spinal drainage; only four patients (2% of the total group) required subsequent surgery for correction of cerebrospinal fluid leakage. There were two deaths (1%) in this series. One death occurred as the result of myocardial infarction and the other as the result of severe obstructive lung disease. One patient sustained disability because of cerebellar and brain stem injury. Complete tumor resection was accomplished in 99% of the patients, and there was no evidence of recurrence in this group. Only 1 of the 179 patients underwent incomplete tumor resection; he required subsequent surgery for symptomatic tumor regrowth. Our patient follow-up had a mean duration of 70 months and a median of 65 months (range, 3-171 mo). CONCLUSION Our results are similar to those of other large microsurgical series of acoustic neuromas. Unless a patient has major medical problems, microsurgery by an experienced team of surgeons is preferred over radiosurgery.

Staging Proposal for External Auditory Meatus Carcinoma Based on Preoperative Clinical Examination and Computed Tomography Findings

An accepted staging system for squamous cell carcinoma of the external auditory meatus is currently lacking and would permit accurate comparison of treatment strategies and results for patients with this unusual neoplasm. In order to develop such a staging system we reviewed the prognostic variables and the accuracy of radiographic diagnoses in 39 patients undergoing temporal bone resection for squamous carcinoma of the external auditory meatus. Predictors of poor survival were extensive tumor involvement, facial nerve paralysis, middle ear involvement, and cervical or periparotid lymphadenopathy. In a comparison of 12 specific anatomic sites, computed tomography was found to be an accurate indicator of histopathologically proven tumor invasion. On the basis of this clinical-radiographic-histopathologic analysis, we propose a TNM staging system for external auditory meatus carcinoma utilizing preoperative computed tomography and physical examination. This system fulfills the requirements of the American Joint Committee on Cancer that a staging system should provide a sound basis for therapeutic planning for cancer patients by describing the survival and resultant treatment of different patient groups in comparable form.

Squamous cell carcinoma of the external auditory meatus (canal).

A retrospective study of 35 patients with squamous cell carcinoma of the external auditory meatus treated at the Eye and Ear Hospital of the University of Pittsburgh was performed. The standard treatment was a temporal bone resection that corresponded to the extent of the lesion, followed by postoperative radiation therapy. The tumor extensions, symptoms, treatments, survival rates, and prognostic variables were reviewed. Overall, 12 of 35 patients survived. Lesions limited to the external auditory meatus with no erosion had excellent prognoses. Survival in intermediate lesions with bony erosion or middle ear Involvement was related to the status of surgical margins after partial or subtotal temporal bone resections. Extensive lesions that involved the surrounding soft tissue or dura had poor prognoses. The survival value of total temporal bone resection remains unproved.

Gamma Knife: An Alternative Treatment for Acoustic Neurinomas

Despite surgical advances and technologic means of better monitoring seventh and eighth nerve function intraoperatively, there remains a group of patients for whom alternative methods of treatment are desirable. These include the elderly, those with bilateral tumors or tumors in only hearing ears, individuals with medical contraindications to major surgery, and those who refuse surgical resection. The University of Pittsburgh became the fifth world center and the first in the United States to install the “gamma knife” for stereotactic radiosurgery. On the basis of the pioneering work done at the Karolinska Institute in Stockholm, acoustic tumor patients who fulfill the above criteria are being treated. A tumoricidal single treatment closed-skull radiation dose is given through 201 sharply focused cobalt 60 sources, minimizing the effects on surrounding brain or other tissues. Our early results are discussed and compared to those from more than 200 cases in Stockholm. Complications and expected long-term results are presented.

Aural irrigation with water: a potential pathogenic mechanism for inducing malignant external otitis?

We hypothesized that the forcible introduction of water containing Pseudomonas aeruginosa into the ear canal of a susceptible host (an elderly diabetic with cutaneous hypoperfusion secondary to microangiopathy) was the inciting factor in the development of malignant external otitis. Tap water irrigation of the ears by a physician preceded the onset of symptoms in 61.5% (8/13) of cases of malignant external otitis. Two control subjects with known diabetes mellitus were matched for each patient by sex and age. Both groups were questioned on the nature and degree of aural water exposure, as well as history of ear disease. There were no significant differences between 13 Patients and 26 control subjects for presence of ear disease (hearing loss, chronic infection, prior operations), swimming, showering, bathing, frequency of ear cleaning, or method of ear cleaning (washcloth, cotton applicator). Patients with malignant external otitis had a statistically significant higher incidence of aural irrigation with tap water when compared with control subjects. We suggest that a substantial number of cases of malignant external otitis may be iatrogenic.

Rotational responses in patients with bilateral caloric reduction.

Caloric irrigation and earth vertical axis rotation, both horizontal semicircular canal stimuli, occasionally provide conflicting information about the presence of bilateral vestibular loss. The caloric and rotational responses of an unselected group of 1274 dizzy patients were compared to identify discrepancies between the two tests. Results indicated a poor correlation between the magnitude of response to caloric and rotational stimuli; about half of patients with reduced caloric responses (total eye speed less than or equal to 10 degrees per second) had rotational response magnitudes (at 0.05 Hz and above) that were within normal limits. Our findings confirm that bilateral caloric reduction is not sufficient evidence for diagnosing bilateral vestibular loss and indicate that, in some case, caloric responses may be absent despite apparent normal vestibular sensitivity as assessed by rotational testing.

The Role of Preoperative CT Scans in Staging External Auditory Meatus Carcinoma: Radiologic-Pathologic Correlation Study

Survival is related to the pathologic extent of tumor in external auditory meatus (EAM) carcinoma. This study assesses the validity of preoperative CT scans in staging EAM carcinoma. The accuracy of staging EAM carcinoma with preoperative CT scans was evaluated by comparing radiography and histopathology. Patients who received preoperative CT scan were selected from a retrospective series of 35 temporal bone resections for EAM squamous cell carcinoma. The CT scans were systematically reviewed for tumor involvement in 12 anatomic areas. The histopathology slides for the corresponding patients were reviewed according to the same criteria. CT scan findings accurately diagnosed the extent of tumor involvement identified during histopathologic examination. These tumors demonstrated the capacity to spread along existing anatomic pathways as well as direct bone erosion. We conclude that preoperative CT scans accurately stage EAM squamous cell carcinoma.

Off-Vertical Axis Rotational Responses in Patients with Unilateral Peripheral Vestibular Lesions:

Off-vertical axis rotation (OVAR) stimulates the otolith organs in a manner that is suitable for assessment of the otolith-ocular reflex. To further assess the potential clinical usefulness of OVAR, the eye movement responses of seven patients with surgically confirmed unilateral peripheral vestibular lesions were compared with the eye movement responses of a group of age-matched, healthy, asymptomatic control subjects. Patients and controls were tested with constant velocity rotations that followed a brief period of angular acceleration (velocity trapezoid) using either earth-vertical axis (EVA) rotation or OVAR. Both EVA and OVAR sinusoidal velocity profiles were also performed. Results indicated that each patient had 1) an asymmetric OVAR response, ie, a bias component whose direction was opposite normal when rotating toward the lesioned ear, and 2) a normal modulation component. Population data suggested that patients had 1) a more rapid decay of response than normal subjects during OVAR velocity trapezoids, 2) an increased phase lead as compared to normal subjects during sinusoidal OVAR, and 3) like normal subjects, a less rapid decay of response during OVAR velocity trapezoids than during EVA rotational velocity trapezoids. Taken together, these findings suggest that patients with unilateral peripheral vestibular deficits have abnormal otolith-ocular and semicircular canal—ocular reflexes but that a single labyrinth appears to provide an otolithic signal sufficient for qualitatively normal semicircular canal—otolith interaction.

Preservation of vestibular nerves in surgery of the cerebellopontine angle: Effect on hearing and balance function

INTRODUCTION Small tumors of the cerebellopontine angle (CPA) can frequently be removed with preservation of the auditory and the vestibular portion of the eighth cranial nerve. This study was undertaken to estimate the effect of vestibular nerve preservation on both balance and hearing following surgery. MATERIALS AND METHODS A retrospective study of all cases of CPA lesions between 1987 and 1991 was undertaken. This identified 11 patients in whom either the superior and/or inferior vestibular nerves were preserved. This included eight acoustic neuromas and three meningiomas. The retrosigmoid approach and total tumor extirpation was undertaken in all cases. Patients undertook a vestibular questionnaire, audiometric testing, and evaluation of vestibulo-ocular responses preoperatively and postoperatively. Additionally, static and dynamic platform posturography was performed postoperatively in 9 of 11 patients. RESULTS Follow-up ranged from 6 to 44 months. Of the eight patients with acoustic neuroma, four had a preoperative balance disorder that resolved postoperatively. One patient died of unrelated causes. Of the remaining seven patients with caloric testings, one maintained normal caloric responses. A persistent postoperative phase shift was noted in 4 of the 7 cases with rotatory testing. Three patients were treated for a meningioma. All had a preoperative balance disorder that resolved postoperatively. Two patients showed vestibular response indicative of residual but compromised function on the involved side. The third patient showed absent responses indicating an anatomically intact nerve that does not necessarily predict functional activity. Preservation of the vestibular nerve was associated with preservation of preoperative hearing in five of the patients. This included four of the eight acoustic patients and one of the three meningioma patients. CONCLUSIONS Preservation of the vestibular nerve did not result in a chronic balance disorder in this patient population. This study does not allow the authors to conclude if vestibular nerve preservation improves overall hearing after CPA surgery; however, these data suggest that preservation of the inferior vestibular nerve may result in less damage to the cochlear nerve in some patients. Accordingly, preservation of the vestibular nerve in CPA meningioma surgery can be recommended.

Electromyographic correlation of tensor tympani and tensor veli palatini muscles in man.

It is the purpose of this study to attempt a correlation of function, by electromyographic means, of the tensor tympani and tensor veli palatini muscles in humans. Despite the small number of patients tested, it is believed that the similarities and characteristics of the two are unmistakably equivalent. A separate theory for the combined tensor function is discussed in distinction to the stapedius mediated acoustic reflex. The concept of a single tensor muscle, with two anatomic divisions, a common nerve supply, and parallel function, is therefore submitted.