Separating Posterior-circulation Stroke from Vestibular Neuritis with Quantitative Vestibular Testing

Abstract Objective To separate vestibular neuritis (VN) from posterior circulation stroke (PCS) using quantitative tests of canal and otolith function. Methods Video-Head-Impulse tests (vHIT) were used to assess all three semi-circular-canal pairs; vestibulo-ocular reflex (VOR) gain and saccade metrics were examined. Cervical and ocular-vestibular-evoked myogenic potentials (c- and oVEMP) and Subjective Visual Horizontal (SVH) were used to assess otolith-function. Results For controls (n=40), PCS (n=22), and VN (n=22), mean horizontal-canal VOR-gains were 0.96±0.1, 0.85±0.3 and 0.40±0.2, refixation-saccade prevalence was 71.9±41, 90.7±57, 209.2±62 per 100 impulses and cumulative-saccade amplitudes were 0.9±0.4°, 2.4±2.2°, 8.0±3.5°. Abnormality-rates for cVEMP, oVEMP and SVH were 38%, 9%, 72% for PCS, and 43%, 50%, 91% for VN. A gain ≤0.68, refixation-saccade prevalence of ≥135% and cumulative-saccade amplitudes ≥5.3° separated VN from PCS with sensitivities of 95.5%, 95.5%, and 81.8%, and specificities of 68.2%, 86.4% and 95.5%. VOR-gain and saccade prevalence when combined, separated VN from PCS with a sensitivity and specificity of 90.9%. Abnormal oVEMP asymmetry-ratios were of low sensitivity (50%) but high specificity (90.9%) for separating VN from PCS. Conclusion vHIT provided the best separation of VN from PCS. VOR-gain, refixation-saccade prevalence and amplitude were effective discriminators of VN from PCS. Significance vHIT and oVEMP could assist early identification of the aetiology of Acute Vestibular Syndrome in the Emergency Room.