Risk factors associated with vestibular nerve schwannomas.

INTRODUCTION: Vestibular nerve schwannoma is a benign tumor that originates in the sheath of Schwann of the eighth cranial nerve. It is considered one of the most common benign intracranial tumors, and its cause is unclear. OBJECTIVE: To identify the risk factors associated with vestibular nerve schwannomas. METHODS: A hospital-based exploratory case-control study was conducted between 2006 and 2010 in 2 municipalities in the northeast region of Brazil. We included individuals with unilateral vestibular nerve schwannomas confirmed by imaging. The controls, selected from the same institutions as the cases, exhibited unilateral hearing loss or tinnitus and had undergone investigatory examinations similar to those of the cases, but the presence of tumor had been excluded. A pretested structured questionnaire, administered by trained interviewers who were blind to the condition of the individual being interviewed, was used to obtain sociodemographic data and data on potential risk factor exposure. We performed a multivariate analysis using unconditional logistic regression. RESULTS: A total of 44 patients with vestibular nerve schwannomas and 104 controls participated in the study. A history of chicken pox (odds ratio, 6.59; 95% confidence interval, 2.07-20.9) and the exposure to more than 1 cranial x-ray procedure (odds ratio, 4.55; 95% confidence interval, 1.10-19.2) were identified as potential risk factors. CONCLUSION: This exploratory study brings new hypotheses to be tested and thus works toward clarifying the causes and mechanisms involved in the cause and development of vestibular nerve schwannoma.

História do diagnóstico do neurinoma do acústico / History of the diagnosis of the acoustic neuroma

É realizada revisao da literatura sobre os neurinomas do acústico, abordando a incidência, as manifestaçoes clínicas, a propedêutica e o diagnóstico diferencial desses tumores. A designaçao mais precisa seria schwannoma do vestibular. Esses tumores constituem 8-10 por cento dos tumores intracranianos, com maior incidência no sexo feminino e na quarta década da vida. As observaçoes sugerem que as manifestaçoes clínicas dos tumores intracanaliculares diferem daquelas dos neurinomas de maior tamanho, existindo formas atípicas de apresentaçao. O crescimento tumoral pode ser diferente nos neurinomas da neurofibromatose tipo II. Os exames por RM e por TC de alta resoluçao para os ossos temporais sao, atualmente, os mais utilizados, existindo ainda, em certos casos, dificuldades no diagnóstico diferencial entre neurinoma do acústico e meningeoma.

Cranial nerve length predicts the risk of delayed facial and trigeminal neuropathies after acoustic tumor stereotactic radiosurgery.

PURPOSE: To test the hypothesis that length of cranial nerve irradiated is a major factor predicting the risk of cranial nerve injury following radiosurgery and to identify any other significant related treatment factors. METHODS AND MATERIALS: Ninety-two patients (93 acoustic tumors) were treated with a 201 source Cobalt-60 gamma unit from 1987 to 1990 and prospectively followed. The range of minimum tumor dose was 12-20 Gy and maximum dose 24-50 Gy. Univariate and multivariate analyses were used to evaluate any correlations between tumor measurements and treatment factors, with the development of trigeminal and facial neuropathies following radiosurgery. RESULTS: The risks of trigeminal and facial neuropathy following radiosurgery were associated with the pon-petrous distance and mid porous transverse tumor diameters respectively (anatomically related to the irradiated length of cranial nerves V and VII respectively) in both univariate (p = .002 for V and p = .026 for VII) and multivariate (p = .004 for V and p = .055 for VII) analyses. Tumor volume, other tumor measurements, maximum dose, minimum tumor dose, and tumor dose inhomogeneity were not significantly related to either trigeminal or facial neuropathy in univariate and multivariate analyses. CONCLUSION: Within a minimum tumor dose range of 12-20 Gy, the incidence of delayed trigeminal or facial neuropathy depended more on the estimated length of nerve irradiated than the tumor dose or tumor volume. In the future, the risk of delayed facial or trigeminal cranial neuropathy may be reduced significantly by performing radiosurgery when the tumor still has both a small mid-porous transverse diameter and a small pons-petrous distance.