Otologic effects of topical mitomycin C: phase I-evaluation of ototoxicity.

HYPOTHESIS: To determine ototoxicity of topical mitomycin C when placed in the middle ear at varying concentrations. BACKGROUND: Despite meticulous surgical technique and diligent postoperative care, some patients develop excessive scar and granulation tissue in the middle ear or mastoid cavity. Poor wound healing may result in infection, tympanic membrane perforation, or conductive hearing loss, which may necessitate further surgery. Use of topical mitomycin C in the ear may be beneficial in reducing scar and granulation tissue formation. This phase of the study was developed to determine the safety of topical mitomycin C in the rat model relative to ototoxicity. METHODS: Twelve Sprague-Dawley rats were evaluated with auditory brainstem response testing before and after treatments. Topical mitomycin C was injected in the middle ear of the right ear of eight animals. Varying concentrations of 0.125 to 0.5 mg/ml were used. Saline was injected in the left ear of each animal to serve as a control. Four separate animals were evaluated with placement of topical mitomycin C on Gelfoam into the middle ear. In two animals, Gelfoam was placed in the middle ear for 1 minute and then removed. In two animals, Gelfoam was placed in the middle ear and left in place. Auditory brainstem response testing was performed at 4 weeks and at 8 weeks. RESULTS: Using a high concentration of mitomycin C (>0.25 mg/ml) resulted in ototoxicity, with an increase in the auditory brainstem response threshold at 4 weeks and at 8 weeks. At low concentrations (<0.20 mg/ml), no change in auditory brainstem response threshold was noted. Animals treated with Gelfoam soaked in mitomycin C showed no change in auditory brainstem response threshold. CONCLUSION: The results of this study indicate that topical mitomycin C on Gelfoam applied in the middle ear appears safe when low concentrations are used, even in the rat, which has a higher susceptibility to gentamycin toxicity than humans. Higher concentrations may lead to ototoxicity based on changes in Wave V on auditory brainstem response. This treatment may prove to be an important option for patients suffering from chronic granulation tissue or scar tissue in the external or middle ear.

Staged resection of large acoustic neuromas.

OBJECTIVE: Surgical removal of large (>3 cm) acoustic neuromas is associated with poor long-term facial nerve function results and higher complication rates. This study analyzes whether long term facial nerve function and the incidence of neurological and vascular complications is improved by resection of large acoustic neuromas in 2 or 3 stages. PATIENTS AND METHODS: Among 660 patients who underwent surgical resection of acoustic neuromas between 1989 and 2002 by the senior author (J.M.K.), 34 (5%) patients underwent a staged resection of their large-sized tumors: stage I via a retrosigmoid craniotomy and stage II via a translabyrinthine approach. A retrospective chart review was performed. Tumor size, completeness of tumor removal, tumor recurrence, facial nerve function, and any complications were noted. RESULTS: The average tumor size was 4.4 cm with a mean postoperative length of follow-up of 6 years after the last surgery. Thirty-one patients underwent a 2-staged resection and 3 patients underwent a 3-staged resection. After their last surgery, 32 (94%) patients had excellent long-term facial function grades of House-Brackmann (H-B) I, one was H-B III, and one was H-B VI. All patients had a total or near-total (>98%) resection. There were no tumor recurrences on follow-up MRI scans. From these 71 operations, no patients required reoperation for a CSF leak. There were no deaths, strokes, hydrocephalus, or meningitis. CONCLUSION: In conjunction with the reported technical refinements, staged resection of large tumors significantly reduces morbidity and improves long-term facial nerve function. EBM RATING: C.

The Chiari I malformation and the neurotologist.

OBJECTIVE: The first objective of this paper is to report the clinical symptoms of 77 patients and the results of their neurologic, vestibular, and audiological evaluations done with magnetic resonance imaging, which confirmed Chiari I malformations. The second objective is to report how the results of a vestibular evaluation can help neurosurgeons decide on the need for surgical treatment. STUDY DESIGN: Retrospective chart review of 77 patients seen between 1988 and 2000. SETTING: Tertiary care center. PATIENTS: The clinical data of patients under diagnoses of Chiari I malformation, which was filed in the vestibular laboratory computer, was analyzed. INTERVENTION: The cases included in this study were derived from a population of patients who were evaluated for dizziness, hearing loss, and tinnitus in the Torok Vestibular Laboratory. MAIN OUTCOME MEASURE: Occurrence of central vestibular findings in the patients with Chiari I malformation. RESULTS: In this group of 77 patients, 10 had bilateral sensorineural hearing loss and 22 had unilateral sensorineural hearing loss of varying severities. Horizontal spontaneous nystagmus was noted in 27 patients, vertical upbeat nystagmus in 3, and downbeat nystagmus in 4 others. Saccadic dysmetria was noted in 4 patients, optokinetic nystagmus was impaired in 3, and smooth-pursuit impairment was noted in 12 of the group. Positional nystagmus was noted in 9 patients. The Torok monothermal caloric test showed normal responses in 19 patients, hyperactive responses in 43, decruitment in 45, and rebound caloric nystagmus in 20. Surgical decompression of the Chiari I malformation was completed in 33 patients. CONCLUSION: From this study it is clear that the results of the basic vestibular function-test battery reflect the functional deficit in the vestibulocerebellum that is presumed by its ectopic position. These tests results have given our neurosurgeons a stronger foundation on which to base surgical decisions for this disease.