Temporal Relationship between Nystagmus and Perception during Bithermal Alternate Caloric Test

Objectives: During caloric irritation, the spinning/rotating sensation is predominant. However, there is no report on the temporal relationship between caloric nystagmus and perception.Methods: Consecutive 57 participants underwent bithermal caloric test in the dizziness clinic of Chungnam National University Hospital from February 2018 to September 2018. For vestibular perception, we asked the subject to report feelings of rotation and/or linear sensation during each warm and cold water irrigation period. Besides routine caloric parameters, the duration of nystagmus and vestibular sensation were analyzed.Results: In most participants, the caloric nystagmus preceded the vestibular sensation (79.6% in right warm, 83.3% in left warm, 88.5% in right cool, and 84.6% in left cool stimuli). The precedence of perception was observed in 5 normal persons and 15 patients with vestibular migraine (n=4), unilateral vestibulopathy (n=3), and Menière’s disease (n=2), multiple systemic atrophy (n=2), cerebellar ataxia (n=2), vertebrobasilar insufficiency (n=1), and post-earthquake dizziness (n=1). The mean latency between nystagmus and perception was 11.7 seconds. And the duration of nystagmus was longer than that of perception in all conditions. Non-spinning sensations during the caloric test were also observed in some participants (26.8% in right warm, 30.3% in left warm, 29.1% in right cool, and 24.1% in left cool stimuli).Conclusions: During the bithemal alternate caloric test, various vestibular perception and temporal relationship between perception and nystagmus suggest the bithermal caloric stimulation does not reflect only the signal originating from the horizontal canal pathway. A further validation study is needed.

Vestibular Impairment in Frontotemporal Dementia Syndrome

Background: No studies to date have attempted to evaluate frontotemporal lobar degeneration from the perspective of the vestibular system. Objective: The present study examined vestibular function in patients with frontotemporal dementia (FTD) clinical syndrome and evaluated whether vestibular disorders are involved in the clinical symptoms due to FTD. Methods: Fourteen patients with FTD syndrome, as well as healthy elderly controls without dementia, were included in the present study. All subjects underwent vestibular function tests using electronystagmography, such as caloric tests and visual suppression (VS) tests, in which the induced caloric nystagmus was suppressed by visual stimuli. The association between clinical symptoms and vestibular function in the FTD syndrome group was further examined. Results: In the FTD syndrome group, caloric nystagmus was not necessarily suppressed during VS tests. Furthermore, VS was observed to be significantly impaired in FTD syndrome patients with gait disturbance as compared to those without such disturbance. Conclusion: The present study revealed that impairment of VS in patients with FTD results in an inability to regulate vestibular function by means of visual perception, regardless of multiple presumed neuropathological backgrounds. This could also be associated with gait disturbance in patients with FTD syndrome.