The Chiari I malformation and the neurotologist

Abstract

Objective: The first objective of this paper is to report the clinical symptoms of 77 patients and the results of their neurologic, vestibular, and audiological evaluations done with magnetic resonance imaging, which confirmed Chiari I malformations. The second objective is to report how the results of a vestibular evaluation can help neurosurgeons decide on the need for surgical treatment.

Study design: Retrospective chart review of 77 patients seen between 1988 and 2000.

Setting: Tertiary care center.

Patients: The clinical data of patients under diagnoses of Chiari I malformation, which was filed in the vestibular laboratory computer, was analyzed.

Intervention: The cases included in this study were derived from a population of patients who were evaluated for dizziness, hearing loss, and tinnitus in the Torok Vestibular Laboratory.

Main outcome measure: Occurrence of central vestibular findings in the patients with Chiari I malformation.

Results: In this group of 77 patients, 10 had bilateral sensorineural hearing loss and 22 had unilateral sensorineural hearing loss of varying severities. Horizontal spontaneous nystagmus was noted in 27 patients, vertical upbeat nystagmus in 3, and downbeat nystagmus in 4 others. Saccadic dysmetria was noted in 4 patients, optokinetic nystagmus was impaired in 3, and smooth-pursuit impairment was noted in 12 of the group. Positional nystagmus was noted in 9 patients. The Torok monothermal caloric test showed normal responses in 19 patients, hyperactive responses in 43, decruitment in 45, and rebound caloric nystagmus in 20. Surgical decompression of the Chiari I malformation was completed in 33 patients.

Conclusion: From this study it is clear that the results of the basic vestibular function-test battery reflect the functional deficit in the vestibulocerebellum that is presumed by its ectopic position. These tests results have given our neurosurgeons a stronger foundation on which to base surgical decisions for this disease.