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Objective-To determine if slight descent of the cerebellar tonsils (< 5 mm below the foramen magnum; tonsillar ectopia) may cause surgically treatable symptomatology. Methods-A consecutive series of nine symptomatic patients with tonsillar ectopia seen between December 1990 and March 1993 are reported on. The same number of age and sex matched controls were selected at random from outpatients. Twelve asymptomatic subjects with tonsillar ectopia were found among 5000 people between January 1991 and March 1996. Diagnosis of tonsillar ectopia was based on midsagittal MRI. Results-Patients presented mainly with chronic intractable occipital dull pain, vertigo, and dysequilibrium. In all patients MRI showed normal brain structure except for tonsillar ectopia (-2.9 (SD 0.8) mm), which has historically been thought to be of no clinical relevance. In the control group the tonsilar position was +2.1 (SD 2.8) mm (p<0.01). Neurotologically abnormal findings were detected with a monaural speech integration test (100%), eye tracking test (56%), optokinetic nystagmus test (89%), and visual suppression test (67%) which strongly suggested a CNS lesion. In accordance with the results of MRI and precise neurotological examination, posterior fossa decompression surgery was carried out, followed by improvement of preoperative symptoms and less severity of neurotological abnormalities in all patients. Conclusion-Tonsillar ectopia could cause neurological symptoms in small populations, which were surgically treatable. Neurotological assessment was necessary to verify the aetiological relation between tonsillar ectopia and various symptoms. (J Neurol Neurosurg Psychiatry 1998;64:221-226)

Postoperative improvements in hearing in patients with vestibular schwannoma are extremely rare. We reviewed nine cases retrospectively to investigate the clinical features of these cases. Hearing improvement was defined as an improvement in hearing class according to American Academy of Otolaryngology-Head and Neck Surgery (AAO-HNS) criteria. The nine patients comprised five men and four women with a mean age of 40.4 years. Of the nine tumors, three were solid and six cystic; mean tumor size was 29.7 mm. Mean pure tone average (PTA) and mean speech discrimination scores (SDS) were 47.5 dB and 22.8%, respectively, preoperatively and 29.6 dB and 83.9%, respectively, postoperatively. AAO-HNS class distribution was class B:1 and D:8, preoperatively, and class A: 5 and B:4, postoperatively. A lateral suboccipital retrosigmoid approach with a lateral (park bench) position was used in all nine patients. Clinical features of these vestibular schwannomas included (1) large cystic tumors, (2) sudden onset hearing loss, (3) the presence of a valley shape in the middle-pitch area on preoperative audiograms, (4) almost intact preoperative inner ear function, (5) a low SDS relative to PTA preoperatively, (6) surgical treatment via a lateral suboccipital approach within 6 months of the most recent exacerbation of hearing loss, (7) observation of I waves in preoperative, intraoperative, and postoperative auditory brainstem response (ABR) recordings, and (8) postoperative improvement in mainly the middle-pitch range and SDS. For surgical treatment of vestibular schwannomas with the above clinical features, a translabyrinthine approach and cochlear nerve section (unless the I wave on the intraoperative ABR trace disappears) should be avoided, regardless of the patient's preoperative hearing level, if a surgeon hopes to maximize the chances of preserving or improving hearing.

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