Ocular motor dysfunction in patients with multiple system atrophy and Parkinson's disease

Differentiating multiple system atrophy (MSA) from Parkinson's disease (PD) remains challenging. This study aimed to investigate the utility of specific ocular motor features in distinguishing MSA from PD, as these dysfunctions may offer valuable diagnostic clues.

We used video-oculography to assess spontaneous nystagmus, saccadic intrusions or oscillations, gaze, saccades, head shaking, positional nystagmus, and vestibulo-ocular reflex (VOR) cancellation in 23 MSA patients and 49 PD patients.

Spontaneous downbeat nystagmus, saccadic intrusions/oscillations, and perverted head shaking nystagmus (pHSN) didn't differ between groups. Horizontal gaze-evoked nystagmus (GEN) occurred in MSA patients but not in PD (P = 0.009). MSA showed significantly more prolonged saccade latency (both horizontal and vertical) and vertical saccadic hypermetria than PD (all P < 0.05). Central positional nystagmus (CPN) was more common in MSA (P = 0.046). Impaired VOR cancellation was significantly higher in MSA than in PD (95.7 % vs. 32.7 %, P < 0.001).

MSA exhibits significantly more pronounced VOR cancellation deficits, horizontal GEN, CPN, saccadic hypermetria, and prolonged saccade latency than PD. These findings suggest a link to the more widespread neurodegeneration characteristic of MSA.

Impaired VOR cancellation, horizontal GEN, saccadic hypermetria, and CPN offer potential for distinguishing MSA from PD.