Lessons from follow-up examinations in patients with vestibular neuritis: how to interpret findings from vestibular function tests at a compensated stage.

Objectives: Most patients complaining of dizziness seek medical services in the interictal period, which is thought to be a compensated stage. Thus, we wanted to investigate the results of vestibular function tests (VFTs) at a compensated stage in patients with vestibular neuritis to determine the presence and the sides of vestibular hypofunction.

Study Design: Retrospective case series review.

Methods: We analyze the results of VFT including spontaneous nystagmus (SN), caloric, vibration-induced nystagmus (VIN), head-shaking nystagmus (HSN), and subjective visual vertical (SVV) tests in 38 patients (M/F = 23:15; age range, 15-85 yr) with vestibular neuritis observed at around 2 months after the onset of vertigo.

Results: Thirty-seven (97%) of 39 patients showed pathologic results in at least 1 test. Pathologic results, based on caloric, SN, VIN, HSN, and SVV tests, were observed in 29 (76%), 20 (53%), 24 (63%), 33 (87%), and 15 patients (39%). Twenty-nine showed pathologic canal paresis (CP) on the affected side and 9 patients (24%) showed normal CP. There was no patient with pathologic CP on the intact side. In 29 patients with pathologic CP, pathologic results, based on SN, VIN, HSN, and SVV tests, were observed in 16 (55%), 20 (69%), 26 (90%), and 13 patients (45%). Three (10%) of 29 patients showed pathologic VIN or HSN, indicating that the intact side is pathologic. In 9 patients with normal CP, pathologic results, based on SN, VIN, HSN, and SVV tests, were observed in 4 (44%), 4, 7 (78%), and 2 patients (22%). Five (56%) of 9 patients showed pathologic results on the intact side at least in 1 test, and the pathologic sides by each test were not the same.

Conclusion: Our findings suggest that we can detect vestibular imbalance in patients with unilateral vestibular hypofunction through a set of VFTs even when CP is normal at a compensated stage. The CP side indicated by caloric test was the real affected side when CP was pathologic, even if the results of other tests were normal or rarely indicated that the intact side was pathologic. If CP was within reference range, other tests can show the previous presence of vestibular imbalance; however, they could not predict the side of the vestibular hypofunction. These data provide strong support for enrolling a set of VFT when evaluating a dizzy patient.