Analysis of video head impulse test saccades data in patients with vestibular migraine or probable vestibular migraine

Objective: Saccades accompanied by normal gain in video head impulse tests(vHIT) are often observed in patients with vestibular migraine(VM). However, they are not considered as an independent indicator,reducing their utility in diagnosing VM. To better understand clinical features of VM, it is necessary to understand raw saccades data.Methods: Fourteen patients with confirmed VM, 45 patients with probable VM(p-VM) and 14 agematched healthy volunteers were included in this study. Clinical findings related to spontaneous nystagmus(SN), positional nystagmus(PN), head-shaking nystagmus(HSN), caloric test and vHIT were recorded. Raw saccades data were exported and numbered by their sequences, and their features analyzed.Results: VM patients showed no SN, PN or HSN, and less than half of them showed unilateral weakness(UW) on caloric test. The first saccades from lateral semicircular canal stimulation were the most predominant for both left and right sides. Neither velocity nor time parameters were significantly different when compared between the two sides. Most VM patients(86%) exhibited small saccades, around 35% of the head peak velocity, with a latency of 200-400 ms. Characteristics of saccades were similar in patients with p-VM. Only four normal subjects showed saccades, all unilateral and seemingly random.Conclusions: Small saccades involving bilateral semicircular canals with a scattered distribution pattern are common in patients with VM and p-VM.