BACKGROUNDDetermining the nerve of origin for vestibular schwannoma (VS), as a method for predicting hearing prognosis, has not been systematically considered. The vestibular test can be used to investigate the function of the superior vestibular nerve (SVN) and the inferior vestibular nerve (IVN). This study aimed to preoperatively distinguish the nerve of origin for VS patients using the vestibular test, and determine if this correlated with hearing preservation.

METHODSA total of 106 patients with unilateral VS were enrolled in this study prospectively. Each patient received a caloric test, vestibular-evoked myogenic potential (VEMP) test, and cochlear nerve function test (hearing) before the operation and 1 week, 3, and 6 months, postoperatively. All patients underwent surgical removal of the VS using the suboccipital approach. During the operation, the nerve of tumor origin (SVN or IVN) was identified by the surgeon. Tumor size was measured by preoperative magnetic resonance imaging.

RESULTSThe nerve of tumor origin could not be unequivocally identified in 38 patients (38/106, 35.80%). These patients were not subsequently evaluated. In 26 patients (nine females, seventeen males), tumors arose from the SVN and in 42 patients (18 females, 24 males), tumors arose from the IVN. Comparing with the nerve of origins (SVN and IVN) of tumors, the results of the caloric tests and VEMP tests were significantly different in tumors originating from the SVN and the IVN in our study. Hearing was preserved in 16 of 26 patients (61.54%) with SVN-originating tumors, whereas hearing was preserved in only seven of 42 patients (16.67%) with IVN-originating tumors.

CONCLUSIONSOur data suggest that caloric and VEMP tests might help to identify whether VS tumors originate from the SVN or IVN. These tests could also be used to evaluate the residual function of the nerves after surgery. Using this information, we might better predict the preservation of hearing for patients.

Adult ; Female ; Hearing ; Humans ; Male ; Neuroma, Acoustic ; pathology ; physiopathology ; Vestibular Nerve ; physiology

Humans ; Neoplasms, Cystic, Mucinous, and Serous ; pathology ; therapy ; Neuroma, Acoustic ; pathology ; therapy

Adult ; Female ; Humans ; Magnetic Resonance Imaging ; Neuroma, Acoustic ; pathology ; surgery

OBJECTIVE: By detecting the myelin structure in acoustic tumor tissues, the cell origin and state of acoustic tumor tissues were investigated. METHOD: Immunofluorescence labeling, immunoblot analysis and electron microscopic study were performed to identify myelin structure and myelin protein in acoustic tumor tissues. RESULT: In this work, we found some early stage of myelin forming in acoustic tumor tissues, but there were no axon nor compact myelin formed and the myelin basic protein whose expression indicates the beginning of myelination was negative detected. We also found that the cell of acoustic tumor express p75,a marker for immature Schwann cells and mature non-myelin-forming Schwann cells. CONCLUSION The date shown in this experiment indicates that the cell of acoustic tumor is in a remyelinating state.
Humans ; Microscopy, Electron ; Myelin Sheath ; pathology ; ultrastructure ; Neuroma, Acoustic ; pathology ; Schwann Cells ; pathology

OBJECTIVETo clarify the expression and subcellular localization of merlin in vestibular schwannoma.

METHODSFifty four paraffin embedded vestibular schwannoma samples confirmed by pathology after resection were included in the study. The expression of merlin in vestibular schwannoma was analyzed by immunohistochemistry. Nerve tissues that were resected during surgical treatment for trigeminal neuralgia and Meniere's disease were used as control. Western blotting was used to analyze the electrophoresis migration of merlin in the acoustic neuroma. Image analysis was used to calculate the positive expression percentage of merlin in each individual. The expression percentage of merlin in the tumor tissue was compared with age and gender of the patients, clinical course of the tumor, tumor growth index, tumor diameter and clinical stage.

RESULTSMerlin was expressed in 0 to 87.5% of the cells in vestibular schwannoma tissue with a mean of (46.66 +/- 5.75)%. There was a negative correlation between merlin expression percentage and tumor growth index. There were no correlations between merlin expression percentage and the age, gender, tumor diameter and clinical stage. There exists a difference for the location of merlin, mainly in the nucleus and perinucleus. There was also a cytoplasmic location. Merlin in the tumor tissue was shown by western blot to be in 65000 and 125000 positions.

CONCLUSIONSMerlin was expressed in vestibular schwannoma tissue, with a different intra-cellular location. Merlin might also exist as a complex with other proteins in the tumor tissue.

Adult ; Aged ; Female ; Humans ; Male ; Middle Aged ; Neoplasm Recurrence, Local ; Neoplasm Staging ; Neurofibromin 2 ; metabolism ; Neuroma, Acoustic ; metabolism ; pathology ; Young Adult

BACKGROUNDSchwannoma is the tumor arising mainly from the cranial and spinal nerves. Bilateral vestibular schwannoma is the hallmark of neurofibromatosis type 2 (NF2). The NF2 gene has been cloned with comprehensive analysis of its mutations in schwannoma. However, most studies focused on vestibular schwannoma. There are differences in proliferation of tumor cell and ultrastructure between vestibular and spinal schwannomas. It is unknown whether genetic alterations in vestibular schwannoma are different from those in non-vestibular schwannoma. We analyzed the loss of heterozygosity (LOH) on chromosome 22 in patients with sporadic schwannoma including vestibular and spinal schwannomas and correlated this genetic alteration with tumor proliferation.

METHODSIn 54 unrelated patients without clinical NF1 or NF2, 36 patients had sporadic vestibular schwannoma, and 18 dorsal spinal root schwannoma. Four highly polymorphic linkage to NF2 gene microsatellite DNA markers (D22S264, D22S268, D22S280, CRYB2) were used to analyze LOH. The proliferative index was evaluated by Ki-67 and proliferative cell nuclear antigen (PCNA) immunostaining. Student's t test was used to analyze the difference of the proliferative index between schwannoma with LOH and that without LOH. The difference of the frequency of LOH in vestibular and spinal schwannomas was investigated by the chi-square test.

RESULTSTwenty-three schwannomas (42.6%, 23/54) showed allele loss. The frequency of LOH in vestibular schwannoma was significantly higher than that in spinal schwannoma (chi2 = 5.14, P < 0.05). The proliferative index of schwannoma with LOH was significantly higher than that without LOH (tki-67 = 2.97, P = 0.0045; tPCNA = 2.93, P = 0.0051).

CONCLUSIONSLOH on chromosome 22 is a frequent event in the tumorigenesis of sporadic schwannoma. And, there is a correlation between LOH on chromosome 22 and proliferative activity in schwannoma. The frequency of LOH in vestibular schwannoma is significantly different from that in spinal schwannoma.

Adult ; Aged ; Cell Proliferation ; Chromosomes, Human, Pair 22 ; Female ; Genes, Neurofibromatosis 2 ; Humans ; Loss of Heterozygosity ; Male ; Middle Aged ; Neurilemmoma ; genetics ; pathology ; Neuroma, Acoustic ; genetics ; Spinal Cord Neoplasms ; genetics ; Spinal Nerve Roots

Medulloblastoma is a common malignant central nervous system neoplasm found mainly in children. One the contrary, medulloblastoma of the cerebellopontine angle, the location of the tumor is very unusual. This is the the first case of the medullomyoblastoma, a rare form of medulloblastoma, occurring in the cerebellopontine angle. A 15-year-old boy experienced a sudden hearing loss in the left ear. Conservative medical treatment failed, and temporal MR imaging revealed a heterogeneously enhancing mass at the left cerebellopontine angle cistern and in the internal auditory canal; therefore, the lesion was regarded as a typical acoustic neuroma. Few days before surgery, an ipsilateral facial palsy developed, and a follow-up MR imaging showed a rapid growth of the previous lesion. The extended translabyrinthine approach permitted surgical removal. And under pathological diagnosis of malignancy, radiation therapy and series of chemotherapy was performed.
Adolescent ; Cerebellar Neoplasms/*pathology/surgery ; Cerebellopontine Angle/*pathology ; Diagnosis, Differential ; Humans ; Magnetic Resonance Imaging ; Male ; Medulloblastoma/*pathology/surgery ; Neuroma, Acoustic/*pathology

BACKGROUND AND OBJECTIVES:Vestibular evoked myogenic potential (VEMP) has become a valuable diagnostic tool evaluating the integrity of sacculocollic reflex and has been done using click sound in most previous clinical trials. This study aims to investigate VEMP responses generated by 500 Hz tone burst in unilateral peripheral vestibulopathy and compare the response with caloric test and subjective visual vertical (SVV). MATERIALS AND METHOD:Clinical records of 37 patients (18 men and 19 women, aged 14-80 years) with unilateral peripheral vestibulopathy were reviewed. Diagnoses were Meniere's disease (n=13), vestibular schwannoma (n=4) and acute peripheral unilateral vestibulopathy (n=20). They underwent 500Hz tone burst VEMP, caloric test and SVV test. Thirteen healthy volunteers (26 ears, 8 men and 5 women, 25~41 years) with normal hearing were enrolled as control group. RESULTS:VEMP response was present in every control ear using 500 Hz tone burst stimuli. In Meniere's disease, VEMPs were positive in 57% (4/7) of patients with abnormal caloric response group and 83% (5/6) with normal caloric response. In acute peripheral vestibulopathy, VEMPs were positive in 47% (9/19) of patients with abnormal caloric response, 0% (0/1) with normal caloric response. The average of CP (canal paresis) in positive VEMP group was 62.4% and that in negative VEMP group was 48.2% (P>0.05). CONCLUSION:Reliable and reproducible test results can be obtained using 500 Hz tone burst stimuli. VEMP results were not in concordance with other vestibular tests, which reflects the dynamic process of dizziness and variable extent of pathology in each case.
Caloric Tests ; Diagnosis ; Dizziness ; Ear ; Evoked Potentials ; Female ; Healthy Volunteers ; Hearing ; Humans ; Male ; Meniere Disease ; Neuroma, Acoustic ; Pathology ; Reflex ; Vestibular Function Tests ; Vestibular Neuronitis

We describe a rare case of malignant transformation in a vestibular schwannoma in a 33-yr-old woman. She presented herself with headache, tinnitus, and hearing loss and underwent posterior fossa explorations three times during the short period of 3 months. The clinicopathological features of the original tumor were typical of benign vestibular schwannoma. Despite a comlpete microsurgical excision, two months later, the tumor recurred locally with a rapid increase in size causing a progressive worsening of neurological symptoms. A diagnosis of malignant schwannoma was made for the recurrent tumor on the basis of the microscopic findings of high cellularity, moderate pleomorphism, and the presence of mitotic cells. Repeat magnetic resonance imaging performed a month after the second surgery unexpectedly showed definite tumor enlargement. She remained clinically stable following the third debulking of the tumor and adjuvant radiotherapy. We propose that this recurrent tumor represent malignant transformation from a benign vestibular schwannoma which was an unusual occurrence in a patient without neurofibromatosis.
Adult ; Case Report ; Cell Transformation, Neoplastic ; Cranial Nerve Neoplasms/*pathology ; Female ; Human ; Magnetic Resonance Imaging ; Neoplasm Recurrence, Local ; Nerve Sheath Tumors/*pathology ; Neuroma, Acoustic/*pathology

BACKGROUND: Intraoperative neurophysiologic monitoring(INM) is well known to be useful method to reduce intraoperative complications during tumor surgery in cerebellopontine angle(CPA). We investigated the changes of INM during the surgery. It might be helpful to keep one's eyes on which monitoring modalities are reluctant to change during the operation. METHODS: We included 49 subjects who had undergone CPA tumor surgery under INM. Their pathology was as follows; vestibular schwannoma in 37, other cranial nerve schwannoma in 3, meningioma in 5 , cyst in 2. The modalities of monitoring were short latency auditory evoked potentials(AEP), somatosensory evoked potentials(SEP) , facial and trigeminal nerve EMG(EMG). Stimulation of SEP was on left or right median, posterior tibial nerves. We studied the frequency of abnormal INM changes and the factors affecting it. RESULTS: The subjects who had abnormal changes in at least one monitoring modality were 19(38.8.%). AEP changes were in 6.1%, SEP in 12.2% and EMG in 24.5%. The AEP monitoring had no potentials from II through V wave in 28 subjects(57.1%). SEP monitoring had improvement in 2 subjects and aggravation in 6, especially involved in median nerve SEP. Tonic EMG activities were observed in 3 facial muscles of 3 subjects, 2 of 4, 1 of 5. Regarding the pathology of tumor, meningioma had much more changed INM than vestibular schwannoma. The volume of tumor was bigger in abnormal INM group than normal group although it is not statistically significant. Also abnormal SEP and EMG group had bigger mass than normal group. CONCLUSIONS: INM has frequent electrophysiologic changes during tumor surgery in CPA. Especially EMG can be changed the most frequently. The larger tumor are, the more frequently abnormal changes in INM of CPA tumor surgery are.
Cerebellopontine Angle* ; Cranial Nerves ; Facial Muscles ; Intraoperative Complications ; Median Nerve ; Meningioma ; Monitoring, Intraoperative ; Neurilemmoma ; Neuroma, Acoustic ; Pathology ; Tibial Nerve ; Trigeminal Nerve