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

Area of Science:

• Neurology
• Ophthalmology
• Neuroscience

Background:

• Differentiating multiple system atrophy (MSA) from Parkinson's disease (PD) is clinically challenging.
• Ocular motor dysfunctions may provide valuable diagnostic clues for neurodegenerative diseases.

Purpose of the Study:

• To investigate the utility of specific ocular motor features in distinguishing MSA from PD.
• To identify key eye movement abnormalities that differentiate these two conditions.

Main Methods:

• Video-oculography was employed to assess various ocular motor parameters.
• Key parameters included spontaneous nystagmus, saccades, gaze-evoked nystagmus (GEN), and vestibulo-ocular reflex (VOR) cancellation.
• The study included 23 MSA patients and 49 PD patients.

Main Results:

• Horizontal GEN was observed in MSA but not in PD (P = 0.009).
• MSA patients exhibited significantly prolonged saccade latency and vertical saccadic hypermetria compared to PD patients (P < 0.05).
• Impaired VOR cancellation was markedly higher in MSA (95.7%) than in PD (32.7%, P < 0.001), and central positional nystagmus (CPN) was more common in MSA (P = 0.046).

Conclusions:

• Multiple system atrophy (MSA) shows significantly more pronounced VOR cancellation deficits, horizontal GEN, CPN, saccadic hypermetria, and prolonged saccade latency than Parkinson's disease (PD).
• These ocular motor findings suggest a link to the more widespread neurodegeneration characteristic of MSA.
• Impaired VOR cancellation, horizontal GEN, saccadic hypermetria, and CPN are potential biomarkers for distinguishing MSA from PD.