Relationship between spontaneous nystagmus and video Head Impulse Test findings among patients with chronic neurotologic conditions

Abstract

The vestibulo-ocular reflex (VOR) in neurotologic patients can be evaluated most quickly by spontaneous nystagmus examinations, and the video Head Impulse Test (vHIT) quantitatively evaluates the VOR of the semicircular canals. We aimed to clarify the concordance and discrepancies between spontaneous nystagmus and vHIT findings, to provide guidance on screening vestibular functions by initial spontaneous nystagmus examination then vHIT. We evaluated 169 outpatients by spontaneous nystagmus examination in the dark using a charge-coupled device camera, then by horizontal vHIT the same day. Vestibular loss on vHIT was defined if both reduced VOR gain (<0.8) and corrective saccade were observed. Adjusted logistic regression modelling revealed that differences in right and left VOR gain positively impacted the presence of nystagmus, which suggests lateralised vestibular dysfunction (P<0.05; odds ratio 1.39 [95% confidence interval, 1.1-1.8] per 0.1 increment). When vHIT is regarded as the standard clinical test, the positive predictive value of nystagmus for vestibular loss on vHIT was 44.4%, and the negative predictive value was 93.5%. The adjusted odds ratio of adults ≥65 years old compared to younger patients associated with a discrepancy of nystagmus and vHIT was significant (2.4 [1.1-5.3]). In conclusion, if spontaneous nystagmus is initially observed in patients, further assessment by vHIT could confirm vestibular dysfunction in 40-50% of cases. If no nystagmus is observed, vHIT might also result in a negative finding in >90% of cases. Older adults appear more likely to show discrepancies between nystagmus and vHIT.

Keywords: Meniere’s disease; Older adults; Spontaneous nystagmus; Vestibular screening; Vestibulo-ocular reflex; Video head impulse test.