Vestibular dose correlates with dizziness after radiosurgery for the treatment of vestibular schwannoma.

BACKGROUND: Stereotactic radiosurgery (SRS) has been recognized as a first-line treatment option for small to moderate sized vestibular schwannoma (VS). Our aim is to evaluate the impact of SRS doses and other patient and disease characteristics on vestibular function in patients with VS. METHODS: Data on VS patients treated with single-fraction SRS to 12 Gy were retrospectively reviewed. No dose constraints were given to the vestibule during optimization in treatment planning. Patient and tumor characteristics, pre- and post-SRS vestibular examination results and patient-reported dizziness were assessed from patient records. RESULTS: Fifty-three patients were analyzed. Median follow-up was 32 months (range, 6-79). The median minimum, mean and maximum vestibular doses were 2.6 ± 1.6 Gy, 6.7 ± 2.8 Gy, and 11 ± 3.6 Gy, respectively. On univariate analysis, Koos grade (p = 0.04; OR: 3.45; 95% CI 1.01-11.81), tumor volume (median 6.1 cm3; range, 0.8-38; p = 0.01; OR: 4.85; 95% CI 1.43-16.49), presence of pre-SRS dizziness (p = 0.02; OR: 3.98; 95% CI 1.19-13.24) and minimum vestibular dose (p = 0.033; OR: 1.55; 95% CI 1.03-2.32) showed a significant association with patient-reported dizziness. On multivariate analysis, minimum vestibular dose remained significant (p = 0.02; OR: 1.75; 95% CI 1.05-2.89). Patients with improved caloric function had received significantly lower mean (1.5 ± 0.7 Gy, p = 0.01) and maximum doses (4 ± 1.5 Gy, p = 0.01) to the vestibule. CONCLUSIONS: Our results reveal that 5 Gy and above minimum vestibular doses significantly worsened dizziness. Additionally, mean and maximum doses received by the vestibule were significantly lower in patients who had improved caloric function. Further investigations are needed to determine dose-volume parameters and their effects on vestibular toxicity.

Correlation between delivered radiation doses to the brainstem or vestibular organ and nausea & vomiting toxicity in patients with head and neck cancers - an observational clinical trial.

OBJECTIVE: Today intensity modulated radiation therapy (IMRT) can be considered the standard of care in patients with head and neck tumors. IMRT treatment plans are proven to reduce acute treatment related side effects by optimal sparing of organs at risk (OAR). At the same time, areas that were out of the former 3D fields now receive low radiation doses. Amongst those areas the brainstem (BS) and the vestibular system (VS) are known to be physiologically connected to nausea and vomiting (NV). In our study we tried to find out, if doses to these areas are linked to NV. MATERIAL & METHODS: NV were assessed at different time points during treatment in 26 patients leading to 98 documented toxicity scores that were later correlated to dose deposition in the described areas. Patients were either treated with normo-fractionated or simultaneously integrated boost IMRT plans in a curative approach. Subareas of the BS as well as the VS were delineated. Toxicity was rated based on the common toxicity criteria (CTCAE Version 4.0). Other factors such as age, gender, chemotherapy, location of the tumor, irradiated volume and unilateral dose to the VS were taken into account and analyzed also. RESULTS: The majority (65.4%) of our patients experienced an episode of NV at least once during treatment. NV was more frequent when treating the oropharyngeal region compared to the hypopharyngeal region, as well as when patients were female and/ or of a younger age. Nevertheless, upon statistical analysis (ROC analysis, 'within/ between analysis') no significant association between delivered doses to subareas and toxicity could be demonstrated. CONCLUSION: In our analysis, no significant correlation between radiation dose to the BS or the VS and the occurrence of NV could be found. Therefore, until conclusive data are available, we recommend to rely on the published data regarding OAR tolerance within the BS and not to compromise on dose coverage.

[Vestibular disorders and nausea during head and neck intensity-modulated radiation therapy]. / Nausées et troubles vestibulaires lors de la radiothérapie conformationnelle avec modulation d'intensité de la tête et du cou.

PURPOSE: We studied whether there is a relationship between nausea and vestibular disorders in patients treated with intensity modulated radiation therapy (IMRT) for head and neck cancer. PATIENTS AND METHODS: We performed a prospective single-centre study that enrolled 31 patients. A videonystagmography was carried out before and within 15 days after radiation therapy for each patient. Nausea was assessed at baseline, every week, and at the post-radiotherapy videonystagmography visit. RESULTS: Twenty-six patients had benefited from a complete interpretable videonystagmography. For 14 of these patients vestibular damage was diagnosed post-radiotherapy. During irradiation, six patients felt nauseous, but without dizziness. In univariate analysis, we found a relationship statistically significant between the average dose received by the vestibules and vestibular disorder videonystagmography (P=0.001, odds ratio [OR]: 1.08 [1.025-.138]), but there was no relationship between vestibular disorder videonystagmography and nausea (P=0.701). CONCLUSIONS: Irradiation of the vestibular system during IMRT does not seem to explain the nausea.

Ruptured distal AICA pseudoaneurysm presenting years after vestibular schwannoma resection and radiation.

Distal anterior inferior cerebellar artery (AICA) pseudoaneurysms are very rare lesions. Although cases have been previously reported, only a few have been reported as a result of vestibular schwannoma (VS) radiation, none have been reported as a result of VS resection, and only one has been reported as treated with parent vessel occlusion (PVO) with n-butyl cyanoacrylate (nBCA). We report a case of a 65-year-old man with a history of right-sided VS surgery and radiation who presented years later with a ruptured pseudoaneurysm of the distal right AICA and was treated with endovascular PVO using nBCA. The aneurysm was completely obliterated and the patient had no worsening of symptoms or neurological exam. The case illustrates a very rare complication of VS surgery and radiation as well as an effective treatment for distal AICA aneurysms.

Does radiation dose to the vestibule predict change in balance function and patient perceived dizziness following stereotactic radiotherapy for vestibular schwannoma?

OBJECTIVE: To date, the majority of the vestibular schwannoma (VS) literature has focused on tumor control rates, facial nerve function and hearing preservation. Other factors that have been shown to significantly affect quality-of-life (QOL), such as dizziness, remain understudied. The primary objective of the current study is to investigate the association between radiation dose to the vestibule and post-treatment changes in vestibular function and patient reported dizziness handicap. MATERIALS AND METHODS: This is a prospective observational pilot study at a tertiary academic referral center including all subjects that underwent linear accelerator-based stereotactic radiotherapy (SRS) for sporadic VS and completed pre-treatment and post-treatment vestibular testing and Dizziness Handicap Inventory (DHI) questionnaires. Associations between objective vestibular test results, patient-reported DHI scores and radiation dose parameters were investigated. RESULTS: Ten patients met inclusion criteria. Tumor control was achieved in all individuals. There were no statistically significant associations or identifiable trends between radiation dose and change in vestibular function or DHI scores. Notably, the four ears receiving the highest vestibular dose had minimal changes in vestibular function tests and DHI scores. CONCLUSIONS: To the best of our knowledge, no previous reports have described the association between radiation dose to the vestibule and post-treatment changes in vestibular function and patient reported DHI. Based on these preliminary data, radiation dose to the vestibule does not reliably predict change in objective or subjective vestibular outcome measures.

Dosimetric predictors of radiation-induced acute nausea and vomiting in IMRT for nasopharyngeal cancer.

PURPOSE: We wanted to investigate dosimetric parameters that would predict radiation-induced acute nausea and vomiting in intensity-modulated radiation therapy (IMRT) for undifferentiated carcinoma of the nasopharynx (NPC). METHODS AND MATERIALS: Forty-nine consecutive patients with newly diagnosed NPC were treated with IMRT alone in this prospective study. Patients receiving any form of chemotherapy were excluded. The dorsal vagal complex (DVC) as well as the left and right vestibules (VB-L and VB-R, respectively) were contoured on planning computed tomography images. A structure combining both the VB-L and the VB-R, named VB-T, was also generated. All structures were labeled organs at risk (OAR). A 3-mm three-dimensional margin was added to these structures and labeled DVC+3 mm, VB-L+3 mm, VB-R+3 mm, and VB-T+3 mm to account for physiological body motion and setup error. No weightings were given to these structures during optimization in treatment planning. Dosimetric parameters were recorded from dose-volume histograms. Statistical analysis of parameters' association with nausea and vomiting was performed using univariate and multivariate logistic regression. RESULTS: Six patients (12.2%) reported Grade 1 nausea, and 8 patients (16.3%) reported Grade 2 nausea. Also, 4 patients (8.2%) complained of Grade 1 vomiting, and 4 patients (8.2%) experienced Grade 2 vomiting. No patients developed protracted nausea and vomiting after completion of IMRT. For radiation-induced acute nausea, V40 (percentage volume receiving at least 40Gy) to the VB-T and V40>=80% to the VB-T were predictors, using univariate analysis. On multivariate analysis, V40>=80% to the VB-T was the only predictor. There were no predictors of radiation-induced acute vomiting, as the number of events was too small for analysis. CONCLUSIONS: This is the first study demonstrating that a V40 to the VB-T is predictive of radiation-induced acute nausea. The vestibules should be labeled as sensitive OARs, and weightings should be considered for dose sparing during optimization in the treatment planning of IMRT.

Radiation effects on the auditory and vestibular systems.

Definitive or postoperative radiation therapy (RT) is commonly used for the management of intracranial and extracranial head and neck tumors. Because of the variability of tumor location and dimensions, sparing of nontarget normal tissue and organs may not be possible. Treatment modalities that deliver the highest doses of radiation to the auditory system include stereotactic radiosurgery (SRS) and fractionated stereotactic radiotherapy (FSRT) for the treatment of vestibular schwannomas (VS), and fractionated radiotherapy (FRT) or intensity-modulated radiation therapy (IMRT) for the treatment of head and neck malignancies. Radiation therapy for VS is unique because of its involvement of the inner ear and preexisting auditory and vestibular dysfunction. Auditory and vestibular dysfunction following RT for VS may be limited by limiting the total dose of cranial nerve VIII irradiation and by fractionation.

The Effect of CO(2) and KTP laser on the cat saccule and utricle.

OBJECTIVES/HYPOTHESIS: To assess the potential carbon dioxide (CO(2)) and potassium-titanyl-phosphate (KTP) laser-related trauma to the saccule and utricle in a cat model. STUDY DESIGN: Basic science experiment utilizing cat model. METHODS: Twelve adult male cats were divided into two groups-CO(2) and KTP-to assess the potential saccule and/or utricle trauma with direct discharge of laser energy into the vestibule after the stapes was removed. Both groups were subdivided to assess the effects with acute sacrifice and three-month survival. Bone conduction auditory brain-stem response thresholds were used to monitor auditory function. Clinical observation was used to monitor vestibular function. The temporal bones were harvested, processed, and stained with hematoxylin and eosin (H&E) in all animals with the uninvolved side serving as the control. RESULTS: None of the animals demonstrated changes in bone conduction auditory brain-stem responses. None of the animals in the survival group demonstrated clinical vestibular dysfunction. Saccular and utricular wall rupture was observed in all animals sacrificed acutely. None of the saccular and utricular wall ruptures were of a size and location that could be attributed to laser trauma, and none of the saccular and utricular wall ruptures were associated with neuroepithelial trauma. CONCLUSIONS: There is no evidence of a difference between the CO(2) and KTP laser in potential laser-related trauma. Using bone-conducting auditory brain-stem response threshold and clinical monitoring of vestibular function, there was no evidence of clinical auditory or vestibular dysfunction. The histologic evidence of saccular and utricular wall rupture is more consistent with stapes extraction trauma than laser-related trauma.

Effects of radiofrequency electromagnetic fields on the human nervous system.

The effects of exposure to radiofrequency electromagnetic fields (EMF), specifically related to the use of mobile telephones, on the nervous system in humans have been the subject of a large number of experimental studies in recent years. There is some evidence of an effect of exposure to a Global System for Mobile Telecommunication (GSM)-type signal on the spontaneous electroencephalogram (EEG). This is not corroborated, however, by the results from studies on evoked potentials. Although there is some evidence emerging that there may be an effect of exposure to a GSM-type signal on sleep EEG, results are still variable. In summary, exposure to a GSM-type signal may result in minor effects on brain activity, but such changes have never been found to relate to any adverse health effects. No consistent significant effects on cognitive performance in adults have been observed. If anything, any effect is small and exposure seems to improve performance. Effects in children did not differ from those in healthy adults. Studies on auditory and vestibular function are more unequivocal: neither hearing nor the sense of balance is influenced by short-term exposure to mobile phone signals. Subjective symptoms over a wide range, including headaches and migraine, fatigue, and skin itch, have been attributed to various radiofrequency sources both at home and at work. However, in provocation studies a causal relation between EMF exposure and symptoms has never been demonstrated. There are clear indications, however, that psychological factors such as the conscious expectation of effect may play an important role in this condition.

Mobile phones: influence on auditory and vestibular systems.

UNLABELLED: Telecommunications systems emit radiofrequency, which is an invisible electromagnetic radiation. Mobile phones operate with microwaves (450900 MHz in the analog service, and 1,82,2 GHz in the digital service) very close to the users ear. The skin, inner ear, cochlear nerve and the temporal lobe surface absorb the radiofrequency energy. AIM: literature review on the influence of cellular phones on hearing and balance. STUDY DESIGN: systematic review. METHODS: We reviewed papers on the influence of mobile phones on auditory and vestibular systems from Lilacs and Medline databases, published from 2000 to 2005, and also materials available in the Internet. RESULTS: Studies concerning mobile phone radiation and risk of developing an acoustic neuroma have controversial results. Some authors did not see evidences of a higher risk of tumor development in mobile phone users, while others report that usage of analog cellular phones for ten or more years increase the risk of developing the tumor. Acute exposure to mobile phone microwaves do not influence the cochlear outer hair cells function in vivo and in vitro, the cochlear nerve electrical properties nor the vestibular system physiology in humans. Analog hearing aids are more susceptible to the electromagnetic interference caused by digital mobile phones. CONCLUSION: there is no evidence of cochleo-vestibular lesion caused by cellular phones.

Telefones celulares: influência nos sistemas auditivo e vestibular: [revisão] / Mobile phones: influence on auditory and vestibular systems: [review]

Os sistemas de telecomunicações emitem radiofreqüência, uma radiação eletromagnética invisível. Telefones celulares transmitem microondas (450-900 MHz no sistema analógico e 1,8-2,2 GHz no sistema digital), muito próximo à orelha do usuário. Esta energia é absorvida pela pele, orelha interna, nervo vestibulococlear e superfície do lobo temporal. OBJETIVO: Revisar a literatura sobre influência dos telefones celulares na audição e equilíbrio. FORMA DE ESTUDO: Revisão sistemática. METODOLOGIA: Foram pesquisados artigos nas bases Lilacs e Medline sobre a influência dos telefones celulares nos sistemas auditivo e vestibular, publicados de 2000 a 2005, e também materiais veiculados na Internet. RESULTADOS: Os estudos sobre radiação do telefone celular e risco de neurinoma do acústico apresentam resultados contraditórios. Alguns autores não encontram maior probabilidade de aparecimento do tumor nos usuários de celulares, enquanto outros relatam que a utilização de telefones analógicos por 10 anos ou mais aumenta o risco para o tumor. A exposição aguda às microondas emitidas pelo celular não influencia a atividade das células ciliadas externas da cóclea, in vivo e in vitro, a condução elétrica no nervo coclear, nem a fisiologia do sistema vestibular em humanos. As próteses auditivas analógicas são mais suscetíveis à interferência eletromagnética dos telefones celulares digitais. CONCLUSÃO: Não há comprovação de lesão cocleovestibular pelos telefones celulares.

Telecommunications systems emit radiofrequency, which is an invisible electromagnetic radiation. Mobile phones operate with microwaves (450-900 MHz in the analogue system; and 1.8-2.2 GHz in the digital system) very close to the user’s ear. The skin, inner ear, cochlear nerve and the temporal lobe surface absorb the radiofrequency energy. AIM: literature review on the influence of cellular phones on hearing and balance. STUDY DESIGN: systematic review. METHODS: We reviewed papers on the influence of mobile phones on auditory and vestibular systems from Lilacs and Medline databases, published from 2000 to 2005, and also materials available in the Internet. RESULTS: Studies concerning mobile phone radiation and risk of developing an acoustic neuroma have controversial results. Some authors did not see evidences of a higher risk of tumor development in mobile phone users, while others report that usage of analog cellular phones for ten or more years increase the risk of developing the tumor. Acute exposure to mobile phone microwaves do not influence the cochlear outer hair cells function in vivo and in vitro, the cochlear nerve electrical properties nor the vestibular system physiology in humans. Analog hearing aids are more susceptible to the electromagnetic interference caused by digital mobile phones. CONCLUSION: there is no evidence of cochleo-vestibular lesion caused by cellular phones.

Modern management of vestibular schwannomas.

Within the last 3 decades, microsurgery and stereotactic radiosurgery (SRS) have become well-established management options for vestibular schwannomas (VSs). Advancement in the management of VSs can be separated into three periods: the microsurgical pioneer period, the demonstration of SRS as a first-line therapy for small and medium-sized VSs, and currently, a period of SRS maturity based on a large worldwide patient accrual. The Marseille SRS experience includes 1,500 patients, with 1,000 patients having follow-up longer than 3 years. A long-term tumor control rate of 97%, transient facial palsy lower than 1%, and a probability of functional hearing preservation between 50 and 95% was achieved in this large series of patients treated with state-of-the-art SRS.

[Effects of electromagnetic fields emitted by cellular phone on auditory and vestibular labyrinth]. / Wirkung elektromagnetischer Felder des GSM-Mobilfunksystems auf auditives und vestibuläres Labyrinth und Hirnstamm.

BACKGROUND: It is the subject of this study to investigate the biological effect of the HF radiation produced by the Global System for Mobile Communications-( GSM)-mobile phone on the inner ear with its sensors of the vestibular and auditive systems. METHODS/PATIENTS: Thermographic investigations made on various model materials and on the human temporal bone should show whether mobile phone does induce any increases of temperature which would lead to a relevant stimulus for the auditive and vestibular system or not. We carried out video-nystagmographic recordings of 13 subjects, brainstem electric response audiometry of 24 ears, and recordings of distorsion products of otoacoustic emissions of 20 ears. All tests were made with and without a mobile phone in use. The data was then analyzed for variation patterns in the functional parameters of the hearing and balance system that are subject to the (non)existence of electromagnetic radiation from the mobile phone. RESULTS: The thermographic investigations suggest that the mobile phone does not induce any increases of temperature which would lead to a relevant stimulus for the auditive and vestibular system. Video-nystagmographic recordings under field effect do not furnish any indication of vestibular reactions generated by field effects. Compared with the recording without field, the brainstem electric response audiometry under field effect did not reveal any changes of the parameters investigated, i. e. absolute latency of the peaks I, III, V and the interpeak latency between the peaks I and V. The distorsion products of otoacoustic emissions do not indicate, comparing the three measuring situations, i. e. before field effect, pulsed field and continuous field, any possible impacts of the HF field on the spectrum or levels of emissions for none of the probands. CONCLUSION: The investigations made show that the electromagnetic fields generated in using the mobile phone do not have an effect on the inner ear and auditive system to the colliculus inferior in the brainstem and on the vestibular receptors in the inner ear and the vestibular system.

Noisy vestibular stimulation improves autonomic and motor responsiveness in central neurodegenerative disorders.

The vestibular nerves are known to influence neuronal circuits in the medullary cardiovascular areas and, through the cerebellar vermis, the basal ganglia and the limbic system. By means of noisy galvanic vestibular stimulation (GVS), it might be possible to ameliorate blunted responsiveness of degenerated neuronal circuits of patients with multi system atrophy or Parkinson's disease, or both. We evaluated the effect of 24-hour noisy GVS on long-term heart rate dynamics in 7 patients with multi system atrophy and on daytime trunk activity dynamics in 12 patients with either levodopa-responsive Parkinson's disease or levodopa-unresponsive parkinsonism. Six of the latter patients were also examined for cognitive performance by means of a continuous performance test. Short-range or high-frequency fluctuations of heart rate were significantly increased by the noisy GVS compared with sham stimulation, suggestive of improved autonomic, especially parasympathetic, responsiveness. Long-range antipersistency of trunk activity patterns probed by an autocorrelation measure was significantly increased by the noisy GVS, suggestive of quickening of bradykinesic rest-to-active transitions. The mean reaction time of the continuous performance test was also significantly decreased by the noisy GVS, without significant changes in either the omission or commission error ratios, which is suggestive of improved motor execution during the cognitive task. In conclusion, the noisy GVS is effective in boosting the neurodegenerative brains of patients with multi system atrophy or Parkinson's disease, or both, including those unresponsive to standard levodopa therapy; it is also effective in improving these patients' autonomic and motor responsiveness.

Can electromagnetic fields emitted by mobile phones stimulate the vestibular organ?

OBJECTIVES: Pulsating electromagnetic (EM) radiation emitted by mobile phones is often incriminated for causing tissue alterations by caloric effects. In particular, the eye and the ear were regarded as possible "hot spots," with heating up to 1 degree C, in which EM radiation might have negative effects. If so, these temperature increments should be large enough to cause vestibular excitation. In this study, we attempted to verify this theory by clinical testing and in vitro experiments. METHODS AND MEASURES: In our laboratory, a simulated GSM signal (889.6 MHz/2.2 W) was applied to 1 ear at a time, while video nystagmography was performed. The experimental setup was similar to that used for caloric (hot and cold water) testing of the peripheral vestibular organ. Data were evaluated by a computer system. There were 13 volunteers (26 ears) included in our study. In an additional experiment, temperatures of human temporal bones were measured by thermography, while a continuous or pulsating EM field was applied. RESULTS: In no volunteer could EM radiation-induced nystagmus be recorded. This corresponds well to our findings that in the human temporal bone very weak caloric effects could only be found in the tissue layers next to the radiation source (antenna of the mobile phone), whereas deeper regions (horizontal semicircular canal) seemed unaffected (at least less than 0.1 degree C). CLINICAL SIGNIFICANCE: These results do not support the theory that mobile phone-induced EM radiation may cause caloric negative effects in the human ear.

[Thermal irritation of the organ of equilibrium by means of heat radiation (NIR)]. / Thermische Reizung des Gleichgewichtsorganes mittels Wärmestrahlung (NIR).

BACKGROUND AND OBJECTIVE: Convection and conduction are the main factors involved in caloric response. Heat radiation has also been discussed as an important factor. The present work tests whether heat radiation is an essential part of the caloric response and whether caloric irritation of the semicircular canals is possible using two sources with a different near infrared (NIR) spectrum. In addition, we tested whether it is possible to induce a detectable nystagmus reaction using either NIR-radiation sources. RESULTS: NIR is able to penetrate bone tissue. The temperature elevation in dry and wet bones was almost immediately registered. With high optical power, specific temperature maxima could be seen by focal and selective broad spectrum and monochromatic NIR irritation of the three semicircular canals. Nystagmus could be generated after using both NIR emission sources in five probands. CONCLUSIONS: NIR generates temperature differences and nystagmus. By using a broad scale as well as a monochromatic NIR-emission source, it is possible to generate a nystagmus. The procedure of NIR-irritation occurs without physical contact, is painless and quiet.

Effect of irradiation on vestibular evoked myogenic potentials in nasopharyngeal carcinoma survivors.

BACKGROUND: This study aims to investigate the effect of irradiation on vestibular evoked myogenic potentials (VEMPs) in nasopharyngeal carcinoma (NPC) survivors, because radiotherapy to NPC covers a column from the basal skull to the clavicle level. METHODS: Twenty-two irradiated NPC survivors and five fresh NPC patients were subjected to VEMP testing, which is evoked by short-tone burst (95 dBHL, 500 Hz) stimulation. Interactions among VEMPs and radiation effects, such as radiation dosage, postirradiation interval, radiation-induced otitis media, sensorineural hearing loss, or canal paresis, were then explored. RESULTS: The mean latencies of p13 and n23 in irradiated ears were significantly delayed compared with either pr-irradiated ears or normal control ears. Delayed VEMPs represented 50% in ears with a mean radiation dosage of 71 Gy, whereas it represented 100% in those with a mean radiation dosage of 123 Gy. Ears with radiation otitis media revealed higher occurrence (65%) of delayed VEMPs than those without radiation otitis media (29%, p <.05), possibly because of radiation sequela affecting the brainstem and neck. However, delayed VEMPs were unrelated to sensorineural hearing loss or canal paresis caused by irradiation. CONCLUSIONS: Delayed VEMPs in NPC survivors are possibly due to radiation-induced otitis media, a brainstem lesion, or neck fibrosis. Hence, VEMP testing may expand the test battery for clinicians to explore balance problems in NPC survivors after irradiation.

Late radiation effects on hearing, vestibular function, and taste in brain tumor patients.

PURPOSE: To investigate late radiation effects on hearing, vestibular function, and taste after conventional radiotherapy in brain tumor patients. METHODS AND MATERIALS: Hearing, vestibular function, and taste were assessed in 33 brain tumor patients irradiated unilaterally to the tumor-bearing hemisphere and the temporal bone. Median observation time after completion of radiotherapy was 13 years; the fraction dose was 1.8 Gy, and mean radiation dose was 53.1 Gy. RESULTS: Deep ulceration in the external ear canal and osteoradionecrosis on the irradiated side was seen in three patients. Reduced hearing was found for air and bone conduction of the irradiated side compared to the opposite side (0.25-2 kHz: 6.1 dB, 4 kHz: 10.3 dB, 6 kHz: 15.6 dB, and 8 kHz: 16.5 dB). For bone conduction, the corresponding figures were 0.25-2 kHz: 5.5 dB and 4 kHz: 8.2 dB. Three patients had a canal paresis of the irradiated side, and three patients had affection of the chorda tympani. CONCLUSION: Irradiation of the temporal bone with doses usually given in the treatment of patients with brain tumors may cause osteoradionecrosis, sensorineural hearing loss, dysfunction of the vestibular inner ear, and loss of taste. Head-and-neck examination should be included in the follow-up of long-term survivors.

[Effects on vestibular function by irradiation in the patients with nasopharyngeal carcinoma].

OBJECTIVE: To investigate effects on vestibular function by irradiation in the patients with nasopharyngeal carcinoma. METHOD: Twenty patients with nasopharyngeal carcinoma were routinely irradiated with dose of 70 Gy (3 cases > 70 Gy). RESULT: Nine cases (45%) were abnormal in vestibular function test after radical irradiation in 20 cases (spontaneous nystagmus n = 3; unlateral canal paresis n = 4; bilateral canal paresis n = 2; bilateral vestibular function absent n = 2). The other 11 cases(55%) were normal in vestibular function test. CONCLUSION: Vestibular function may be damaged after radical irradiation in patients with nasopharyngeal carcinoma. During professional identification, this factor must be respected and vestibular function, cochlear function and tubal function must be separately evaluated.

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.