Quality of hearing preservation in acoustic neuroma surgery

OBJECTIVE: This study aimed to investigate the factors affecting the quality of postoperative hearing in acoustic neuroma. STUDY DESIGN: The study was designed as a retrospective case review. SETTING: The study was performed at the Department of Otolaryngology, School of Medicine, Keio University, Tokyo, Japan. PATIENTS: The subjects were 94 patients with unilateral acoustic neuroma. INTERVENTION: Hearing preservation surgery was performed in the subjects via the extended cranial fossa approach or the middle cranial fossa approach. MAIN OUTCOME MEASURES: The outcome measures included patient's age and gender, hearing level, speech discrimination score, tumor size, and surgical approach. The relationship between the qualities of preoperative and postoperative hearing and the long-term prognosis of preserved hearing also was investigated. RESULTS: In 94 subjects, there were 47 patients whose hearing was preserved (HP group) and 47 patients whose hearing was not preserved (non-HP group). Overall, hearing preservation rate was 50%. There were no significant differences in age, gender, and tumor size between the two groups. The hearing preservation rate was significantly higher in patients with an intracanalicular tumor than that with a larger tumor. The better the preoperative quality of hearing was, the higher the postoperative one. Although the preserved hearing deteriorated after surgery in 4 patients, no significant hearing deterioration was observed in the other 43 patients. CONCLUSIONS: The results of this study indicated that the diagnosis for acoustic neuroma in the early stage with serviceable hearing is the most important to improve the quality of postoperative hearing.     

Radiation tolerance of the cochlear nerve at the gamma-knife in rabbits

Since the first treatment of acoustic neurinoma using the gamma-knife by Leksell, a series of cases have been reported with good control rates. However, the most frequent complication is delayed hearing loss which occurs in more than 50% of patients. The purpose of this study was to define a safe dose by analyzing the radiosurgical dose-response relationship and histological effects on the normal cochlear nerve in rabbit. The rabbits had computed tomography (CT)-guided stereotactic radiosurgery on their cochlear nerves in the internal auditory canal with a 4 mm collimator focusing of a gamma-unit. Maximum doses of 10, 20, 30, 40, 60, 80, 100, 200 and 500 Gy were administered. After the radiosurgery, auditory brain stem responses (ABR) and the behavior of the rabbits were evaluated periodically. At the conclusion, histological investigations were performed. No physiological or histological findings were observed from doses of 30 Gy or below during the 12 month period after the radiosurgery. A dose of 100 Gy caused a severe ABR threshold elevation, vestibular dysfunction and facial palsy. Necrosis and demyelination of nerves were observed pathologically. In this study, we determined that the safe dose to the normal cochlear nerve during radiosurgery was under 40 Gy in rabbits, and complications seemed to vary due to individual differences in radiation tolerance.     

Analyses of neuro-otological complications after radiosurgery for acoustic neurinomas

PURPOSE: To find out the optimum treatment parameters and the proper indications for treatment of acoustic neurinomas, univariate and multivariate actuarial analyses of neuro-otological complications after stereotactic radiosurgery for acoustic neurinomas were performed. METHODS AND MATERIALS: The subjects were 46 patients with acoustic neurinomas who underwent unilateral radiosurgery between June 1990 and June 1994 and were followed up at the University of Tokyo. Age ranged from 13 to 77 years (median, 54 years). Tumor diameter ranged from 0 to 25 mm (mean, 12 mm) at the cerebellopontine angle and from 2 to 15 mm (mean, 8.3 mm) in the internal auditory meatus. Maximum tumor doses ranged from 20 to 40 Gy (mean, 31.4 Gy), and peripheral doses from 12 to 25 Gy (mean, 16.8 Gy). One to eight isocenters were used (mean, 3.2). Median follow-up was 39 months. Eight events concerning neuro-otological complications were chosen, and the potential risk factors for them were analyzed by the actuarial analyses (univariate and multivariate). The events examined include hearing loss, vestibular function loss, facial palsy, and trigeminal nerve dysfunction. In order to point out potential risk factors for neuro-otological complications, univariate analyses were performed using both the Wilcoxon test and the log rank test, and multivariate analyses were performed with the Cox proportional hazards model. Variables nominated as potential risk factors were 1) demographic variables such as patient age and sex, 2) tumor dimensions, 3) treatment variables such as tumor doses and number of isocenters, and 4) pretreatment hearing levels. A variable with significant p-values (p < 0.05) in two or more of the three actuarial analyses (two univariate and one multivariate) was considered a possible risk factor. RESULTS: The possible variables that increase the risk for each event analyzed were: neurofibromatosis type II (NF2) and the number of isocenters for total hearing loss; experience of prior operation, the tumor diameter in the internal auditory meatus, and NF2 for hearing threshold elevation; peripheral tumor dose for vestibular function loss; patient age or midporus transverse tumor diameter (the two variables were correlated), and the number of isocenters for facial palsy; and the number of isocenters for trigeminal neuropathy. CONCLUSION: NF2 and the tumor diameter were the common risk factors for hearing loss in previous studies and ours. For the 5th/7th nerve dysfunction, the tumor diameter was the common risk factor. The risk of using more isocenters remains controversial. The difference in risk factors for hearing impairment and vestibular function loss suggests different mechanisms for the two. Further studies with larger populations and longer follow-up periods are required in order to draw conclusions on the risk factors in radiosurgery.     

Postnatal development of vascular beta-adrenoceptor-mediated responses and the increase in the adrenaline content of the adrenal gland have a parallel time course

Factors influencing facial nerve preservation and function in acoustic neuroma surgery were studied in 108 cases. Anatomic preservation of the nerve was inversely related to tumor size and improved as the series progressed. When the nerve was saved, normal postoperative function was inversely related to tumor size and was more common if the cochlear nerve was also saved. Most intact nerves eventually recovered some function, but late function was seldom completely normal unless there was some early recovery. The results demonstrate the importance of tumor size, operator experience, and ease of dissection on facial nerve outcome.     

Inhibitory effects of saiboku-to and compornent herbs on the production of peptide leukotrienes (LTs) and LTB4]

We report our early experience using stereotactic radiotherapy (radiosurgery) in the treatment of cranial neuroma, by the linear accelerator method. We report the first 13 neuromas treated in 12 patients (follow-up 6-60 months). Radiologically, seven of 10 patients demonstrated signs of central tumour necrosis on follow-up scanning and four of these also demonstrated shrinkage. Of seven assessable acoustic neuroma patients treated, hearing was stabilized in three and improved in two. An abducent neuroma patient treated by this method is reported and demonstrated good response. Our preliminary studies endorse the opinion that stereotactic radiosurgery is a suitable and safe alternative to microsurgical procedures in the management of many cranial neuromas. Indications for stereotactic radiosurgery are discussed.     

Costs and effects of microsurgery versus radiosurgery in treating acoustic neuroma

This study analyses costs and effects of treating acoustic neuroma patients by using microsurgery compared to radiosurgery. Radiosurgery is the stereotactic application of radiotherapy and an innovative medical technology. Cost and effect estimates of conventional treatment were based on a retrospective study in the Netherlands. Similar data for a comparable group of patients in Sweden were collected for radiosurgery, as this treatment option is currently not available in the Netherlands. Fifty-three acoustic neuroma patients who had been operated on the University Hospital Rotterdam between November 1990 and February 1995 were included. This group was compared with 92 acoustic neuroma patients treated with radiosurgery (Gamma Knife. Stockholm, Sweden) in the same period. Data on health care use were collected from patient files. To obtain data on production losses and quality of life, a questionnaire was sent by mail in February 1995. This booklet consisted of the Health and Labour-questionnaire (HLQ), the Short Form-36 (SF36) and the EuroQol. The response rate was 92%. Direct costs for microsurgery amounted to Dfl. 20.072,- and for radiosurgery to Dfl. 14.272,-. Indirect costs were respectively Dfl. 16.400,- and Dfl. 1.020,-. General health rating was better for radiosurgery than for microsurgery. On the whole, differences in clinical outcomes between the two patient groups were small. Assuming a reasonable occupancy rate of the expensive radiosurgery equipment, we demonstrated that for the short term treating patients with acoustic neuroma with an extra-meatal tumour diameter of less than 3 centimeters, radiosurgery is more cost-effective than microsurgery.     

Hearing preservation in acoustic tumor surgery: results and prognostic factors

A retrospective study was conducted to assess the hearing results in patients who underwent acoustic neuroma removal via the middle fossa approach. A statistical correlation of results with preoperative clinical and audiological data determined if any prognostic indicators could be associated with successful hearing preservation. Of 93 patients included in the study, useful hearing was preserved in 54 (58%), and hearing was preserved near preoperative levels in 42 (45%). The potential for hearing preservation appeared to be inversely related to the size of the acoustic tumor, with hearing preserved in 39 (60%) of 65 patients with tumors less than or equal to 0.5 cm extension into the cerebellopontine angle. Preoperative hearing levels and electronystagmography seemed to have no prognostic value. However, auditory brainstem response showed that a wave V latency of less than 6.8 msec was associated with an increased chance of hearing preservation, and the presence of vertigo as a preoperative complaint appeared to be a good prognostic indicator of successful hearing preservation.     

Preservation of cranial nerve function after treatment of acoustic neurinomas with fractionated stereotactic radiotherapy. Preliminary observations in 26 patients

Twenty-seven acoustic tumors in 26 patients were treated with multiple fractionated linear-accelerator-based stereotactic radiotherapy (SRT). All patients with intact pretreatment facial nerve function with either small or large tumor volumes have thus far experienced no treatment-related facial neuropathy, including 9 patients with a mean follow-up of 22.4 +/- 1.6 months. The incidence of evaluable trigeminal neuropathy was 13%, and in 5 of 7 patients with serviceable pretreatment hearing, audiometry was unchanged in the immediate posttreatment period. Longer follow-up will be necessary to evaluate hearing preservation after SRT. Tumor response with central necrosis was seen in all assessable patients. SRT can be performed for cerebellopontine angle tumors with accuracy and reproducibility. It achieves a biological response similar to single fraction radiosurgery and may lower the incidence of facial and trigeminal neuropathies.     

Preservation of hearing in large acoustic neurinomas following removal via suboccipito-lateral approach

A consecutive series of 61 patients with pre-operative hearing underwent surgical removal of a large acoustic neurinoma via the lateral suboccipital approach between 1984 and 1996. Brain-stem auditory evoked potentials (BAEP) were present in all cases before surgery and all patients underwent intra-operative monitoring of BAEP. The average tumour size including the portion within the meatus acusticus internus was 30, 5 mm (range 20 mm-49 mm). Complete tumour removal was achieved in all but three cases. In 43.1% of patients with complete tumour removal hearing was preserved initially after surgery. Delayed postoperative hearing loss was observed in 11 patients and hearing recovery in 2 patients leading to 27.5% definite hearing preservation. Hearing preservation was achieved in 37% of cases with tumour size between 20 mm-29 mm and in 23.5% of case with tumour size larger than 30 mm. These results indicate that even in large neurinoms hearing preservation should be attempted in all patients with documented pre-operative hearing and BAEP.     

Surgery of inner ear diseases (author's transl)

In the treatment of Menière's disease, surgical procedures are available when conservative measures have failed. The most distressing symptom of vertigo can frequently be arrested, tinnitus reduced and hearing improved. Sudden deafness due to round window rupture is treatable. The most important disorder with labyrinthe symptoms is the acoustic neuroma, the smaller ones of which can be operated on by otologists in collaboration with neurosurgeons using the transtemporal or translabyrinthine approach with preservation of the facial nerve.     

Mortality studies in the clarification of gene-environment interactions

A case is reported in which a Nucleus 22 channel intracochlear implant was applied to a Hungarian woman (age 50 yr) with profound deafness associated with osteogenesis imperfecta. Successful intracochlear insertion of the 22 electrodes resulted in a 70 dB hearing improvement at frequencies 250-2000 HZ. Nevertheless, a characteristic facial twitching appeared upon activation of electrodes 9-13. Inactivation of these electrodes abolished the non-acoustic nerve excitation with preservation of acoustic performance. Osteogenesis imperfecta may involve a state of risk for non-acoustic nerve activation in cochlear implant patients possibly resulting from a reduced impedance to current spread by abnormal bone tissue. This, however can be overcome by simple programming manoeuvres.     

Intraoperative monitoring of facial nerve antidromic potentials during acoustic neuroma surgery

The present paper presents monopolar recording of facial nerve antidromic potentials as an alternative technique to facial electromyography for the continuous monitoring of the facial nerve during acoustic neuroma surgery. The investigation involved 22 patients undergoing acoustic neuroma surgery via a retrosigmoid approach (tumour sizes ranging from 5 to 28 mm). Bipolar electrical stimulation of the marginalis mandibulae was performed to elicit facial nerve antidromic potentials. Stimulus intensity ranged from 2 to 6 mA with a delivery rate of 7/sec. A silver wire monopolar electrode positioned intracranially on the proximal portion of the acoustic facial bundle was used to record antidromic potentials. To define the specific origin of the action potentials and acquire normative data, monopolar and bipolar recordings of facial nerve antidromic potentials were performed in 15 subjects undergoing retrosigmoid vestibular neurectomy for Meniere's disease. The average facial nerve antidromic potential latency was 4.2 (+/- 0.6) msec in subjects with acoustic neuroma and 3.3 (+/- 0.2) msec in subjects with Meniere's disease. Facial nerve antidromic potentials furnished near real-time information about intraoperative facial nerve damage and postoperative facial nerve function during acoustic neuroma surgery. Facial nerve antidromic potentials may provide additional information to conventional EMG. They allow the use of endplate blockers, yield quantitative estimation of facial nerve conduction properties in terms of amplitude and latency, and allow actual continuous monitoring of the facial nerve.     

Intracochlear placement of cochlear implant electrodes in soft surgery technique

It is commonly accepted that the intracochlear placement of the cochlear implant electrode is potentially damaging to the hearing rests which may exist. Consequently, cochlear implants have been recommended for totally deaf ears only. The question has been raised whether or not it is possible to preserve residual hearing during intracochlear implantation through extremely careful surgical techniques. Experience has shown, that the cochleotomy of the scala tympani anterior to the round window niche, careful preservation of the fibrine endost layer and the use of Healon are amongst the surgical procedures described which may assist in retaining the rest function of the inner ear. These observations which are discussed in detail suggest that the experienced surgeon can effect preservation of residual hearing for patients who cannot derive significant benefits from conventional acoustic amplifiers.     

Accuracy of seven different tests for the diagnosis of Helicobacter pylori infection and the impact of H2-receptor antagonists on test results

The financial burden for the evaluation of patients for acoustic neuroma in an otolaryngology practice is substantial. Patients with sudden sensorineural hearing loss represent a portion of that population seen with unilateral, asymmetric auditory symptoms who require investigation for acoustic neuroma. For these patients, gadolinium-enhanced magnetic resonance imaging is the diagnostic gold standard. Auditory brain stem response testing has been used in the past as a screening test for acoustic neuroma, but its apparent sensitivity has fallen as the ability to image smaller acoustic neuromas has improved. Fast spin echo magnetic resonance imaging techniques without gadolinium have been shown to be as effective in the detection of acoustic neuroma as contrast-enhanced magnetic resonance imaging. Limited nonenhanced fast spin echo magnetic resonance imaging now provides an inexpensive alternative for high-resolution imaging of the internal auditory canal and cerebellopontine angle. Fast spin echo magnetic resonance imaging can now be done at a cost approximating auditory brain stem response testing while providing the anatomic information of contrast-enhanced magnetic resonance imaging. Cost analysis was done in the cases of 58 patients with sudden sensorineural hearing loss by comparing the costs for routine workup and screening of acoustic neuroma with the cost of fast spin echo magnetic resonance imaging with the use of screening protocols based on literature review. The potential cost savings of evaluating patients with sudden sensorineural hearing loss with fast spin echo magnetic resonance imaging for acoustic neuroma was substantial, with a 54% reduction in screening costs. In an era of medical economic scrutiny, fast spin echo magnetic resonance imaging has become the most cost-effective method to screen suspected cases of acoustic tumors at our institution by improving existing technology while reducing the cost of providing that technology and eliminating charges for impedance audiometry, auditory brain stem response testing, and contrast-enhanced magnetic resonance imaging.     

Input-output function of the acoustic reflex and objective hearing aid evaluation

Hearing aid evaluation procedures should mainly consider hearing properties in the most comfortable loudness intensity range. This applies to both subjective and objective methods. With regard to this aspect, input-output characteristics of the acoustic reflex were investigated for speech noise and narrow-band noise (0.5, 1, 2 and 4 kHz) stimulation. In these terms, hearing aid evaluation can be understood as an approximation of pathological input-output functions to the normal range by suitable hearing aids. After normal input-output characteristics have been established, we report on first experiences with this fitting procedure. Frequency-specific elicitation of the stapedial reflex with and without hearing aid enables a compensation for hearing impairment in accordance with frequency-dependent dynamic properties.     

Analysis of evoked otoacoustic emissions in patients with high frequency cochlear hearing loss

Evoked otoacoustic emissions (EOAE) and auditory brainstem evoked response (ABR) were tested in patients with high frequency cochlear hearing loss and subjects with normal hearing. Results showed that: 1. In the normal group, the main component of EOAE varied between 0.5-5kHz. 2. There was a close correlation between the pure-tone audiogram figure and EOAE spectrum. 3. The I/O function curves of EOAE displayed non-linear characteristics and a trend of saturation with higher stimulus levels in the normal group. In the patient group the growth rates of EOAE and ABR were remarkably higher than those in the normal group with high stimulus levels. It suggests that the abnormal EOAE are probably relevant to the recruitment phenomenon in cochlear hearing loss.     

Long-term outcomes after radiosurgery for acoustic neuromas

BACKGROUND: Stereotactic radiosurgery is the principal alternative to microsurgical resection for acoustic neuromas (vestibular schwannomas). The goals of radiosurgery are the long-term prevention of tumor growth, maintenance of neurologic function, and prevention of new neurologic deficits. Although acceptable short-term outcomes have been reported, long-term outcomes have not been well documented. METHODS: We evaluated 162 consecutive patients who underwent radiosurgery for acoustic neuromas between 1987 and 1992 by means of serial imaging tests, clinical evaluations, and a survey between 5 and 10 years after the procedure. The average dose of radiation to the tumor margin was 16 Gy, and the mean transverse diameter of the tumor was 22 mm (range, 8 to 39). Resection had been performed previously in 42 patients (26 percent); in 13 patients the tumor represented a recurrence of disease after a previous total resection. Facial function was normal in 76 percent of the patients before radiosurgery, and 20 percent had useful hearing. RESULTS: The rate of tumor control (with no resection required) was 98 percent. One hundred tumors (62 percent) became smaller, 53 (33 percent) remained unchanged in size, and 9 (6 percent) became slightly larger. Resection was performed in four patients (2 percent) within four years after radiosurgery. Normal facial function was preserved in 79 percent of the patients after five years (House-Brackmann grade 1), and normal trigeminal function was preserved in 73 percent. Fifty-one percent of the patients had no change in hearing ability. No new neurologic deficits appeared more than 28 months after radiosurgery. An outcomes questionnaire was returned by 115 patients (77 percent of the 149 patients still living). Fifty-four of these patients (47 percent) were employed at the time of radiosurgery, and 37 (69 percent) remained so. Radiosurgery was believed to have been successful by all 30 patients who had undergone surgery previously and by 81 (95 percent) of the 85 who had not. Thirty-six of the 115 patients (31 percent) described at least one complication, which resolved in 56 percent of those cases. CONCLUSIONS: Radiosurgery can provide long-term control of acoustic neuromas while preserving neurologic function.     

Fear of childbirth during pregnancy may increase the risk of emergency cesarean section

The clinical features of progression sensorineural hearing loss and vertigo in combination with the radiologic finding of a contrast-enhancing mass within the inner auditory canal are suggestive of an acoustic neuroma. We report our findings in a 57-year-old woman with known mixed connective tissue disease who was presumed to have a neuroma. A large malignant lymphoma of the cerebellopontine angle presented clinically with a primary acoustic none palsy and no other central neurological deficits. Both the primary radiological examinations and the exclusively peripheral nerve palsy failed to indicate manifestations of a lymphoma. The development of a progressive facial palsy within 8 weeks of presentation and an atypical occipital headache were uncommon findings for an acoustic neuroma. Such changes in symptoms despite the occurrence of cardinal symptoms require further diagnostic measures. Manifestations of a malignant lymphoma in the cerebellopontine angle are extremely rare. To our knowledge a case of an intracerebral lymphoma in a patient with Sj?gren's syndrome has never been reported before.     

Detection of restricted junctional diversity of peripheral T cells in SLE patients by spectratyping

Three patients presented with unilateral sensori-neural hearing disturbance as the initial symptom of cerebellar tumors: a 19-year-old female with a medulloblastoma (Case 1), a 45-year-old male with a cerebellar low-grade glioma (Case 2), and a 49-year-old female with a cerebellaer hemangioblastoma (Case 3). In Cases 1 and 2, the whole length of the eight cranial nerve was intact according to magnetic resonance imaging and intraoperative findings. In Case 3, the intracerebellar tumor had bulged into the cerebellopontine cistern, compressing the eighth cranial nerve near the brainstem. Auditory evoked brainstem responses showed only the first wave in all three patients, and the following waves could not be discriminated. Unilateral sensori-neural hearing disturbance occurs very rarely in patients with intramedullary cerebellar lesions because the auditory neural pathway is bilaterally innervated. Intramedullary tumors may cause unilateral sensori-neural hearing disturbance by infiltrating or causing edematous changes of the eighth cranial nerve or the cochlear nucleus in the brainstem, or by compressing the nerve in the cistern. The symptoms are the same as those of acoustic neurinoma, so intramedullary cerebellar tumors should be considered in the differential diagnosis of unilateral sensorineural hearing disturbance.     

The electrophysiological indices of the state of the different sections of the auditory analyzer in persons with a normal voice and with functional voice disorders]

Individuals with normal voice and patients with voice functional impairments undergone electrophysiological investigation of various parts of the hearing system, using tone audiometry, including the extended frequency band (10, 12, 14 and 16 kHz), as well as short- and long-latency acoustic evoked potentials (SLAEP and LLAEP). It was found out, that individuals with voice functional impairments had all of their hearing system's parts impaired to various extent, with more marked impairments in the central, rather than in the peripheral part of the hearing system. It was shown, that hearing at 4-8 kHz, as well as with the extended frequency band, especially at 14-16 kHz, time patterns of acoustic evoked potentials (latencies of waves III and V of SLAEP, the interpeak interval I-V, as well as the latency periods of the LLAEP components P2 and N2) could be useful in professional selection of individuals of voice and speech professions and for solving labor expertise matters. Of those individuals with normal voice but systematic vocal stress, 17.5% had impaired hearing at 14 and 16 kHz, as well as significant latency prolongation of the LLAEP wave N2 with tone stimulation at 1 and 4 kHz. Apparently, individuals of voice and speech professions should be referred to as the "risk" group. It may well be, that extended band audiometry and acoustic evoked potentials time patterns could be useful in determining the thresholds between the normality and pathology in voice dysfunctions.