Role of the video head impulse test in the evaluation of vestibulo-ocular reflex in individuals with Parkinson's disease.

Background and purpose:

Parkinson’s disease (PD) is the most common movement disorder and the second most common neu­rodegenerative disease of the central ner­vous system. Dizziness is frequently reported by PD patients, yet there is a paucity of research focusing on the vestibulo-ocular reflex (VOR) in this population using high-frequency vestibular testing. This study aims to investigate the VOR in individuals with PD using the video head thrust test with and without suppression. 

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Methods:

Forty individuals with PD and 40 healthy individuals were included in the study. According to the Hoehn-Yahr Scale, individuals with PD were defined as early stage with a score of 1–2.5 and middle to late stage with a score of 3 to 5. The Head Impulse Testing Paradigm (HIMP) and Suppression Head Impulse Testing Paradigm (SHIMP) were applied to all individuals.

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Results:

No statistically significant difference was observed between the PD group and the control group in terms of semicircular canal (SCC) gains in both HIMP and SHIMP tests. No catch-up saccades were observed in the right anterior, right posterior, left anterior, and left posterior SCC planes in the PD and control groups. However, in the right lateral SCC plane 32 patients in the PD group had saccades, while 8 patients in the control group had saccades. In the left lateral SCC plane, 32 patients in the PD group and 9 patients in the control group had catch-up saccades. A statistically significant difference was observed in the number and amplitude of saccades in the right and left lateral SCC planes compared to the control group (p<0.05). In addition, in the PD group, the amplitude, peak velocity, and latency of the anticompensatory saccades seen in SHIMP showed a statistically significant difference compared to the control group (p<0.05).

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Conclusion:

VOR in the vertical SCC plane was not affected in individuals with PD. However, VOR in the lateral SCC plane was affected. It was concluded that when evaluating VOR with both HIMP and SHIMP in individuals with PD, the presence of catch-up saccades should be focused on and evaluated for possible vestibular dysfunction, even though SCC gains are normal. This study will contribute to a deeper understanding of vestibular function in PD, potentially informing better management strategies for dizziness in this population. 

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