Objective: To investigate the pupillary autonomic function and oculomotor characteristics of patients with multiple system atrophy (MSA).

Background: MSA is a debilitating neurodegenerative disorder with combinations of Parkinsonism, cerebellar ataxia and autonomic dysfunction. Although urinary incontinence and orthostatic hypotension are the major autonomic dysfunction, there is little information about the pupillary autonomic dysfunction and oculomotor abnormalities in MSA patients.

Methods: We analyzed clinical data of 19 clinically probable or possible MSA patients. Severity of MSA was assessed by the United Multiple System Atrophy Rating Scale (UMSARS). Pupillary autonomic function was quantitatively evaluated with dynamic pupillometry (NeurOptics NPi-100 Pupillometer) in 12 MSA patients, including parameters of neurological pupil index (NPi), percentage of pupil size change (%CH), latency (LAT), constriction velocity (CV), maximum constriction velocity (MCV) and dilation velocity (DV). The average of the patient’s two eyes was used. Partial correlation analysis controlling for age was performed. Oculomotor abnormalities was objectively measured by electro-oculography in 14 MSA patients, including spontaneous and gaze-evoked nystagmus, head shaking nystagmus, range of eye movement, sinusoidal smooth pursuit, saccade, and optokinetic response on both horizontal and vertical directions.

Results: The DV in pupillary autonomic test showed the most significant association with UMSARS score (Pearson’s R = -0.822, P = 0.002). The %CH (Pearson’s R = -0.787, P = 0.004) and NPi (Pearson’s R = -0.702, P = 0.016) also showed significant association with UMSARS score. In oculomotor function tests, hypometric horizontal saccade and broken-up horizontal smooth pursuit eye movements were detected almost universally in MSA patients. Blepharospasm was in 5 (26%) of 19 MSA patients.

Conclusions: This study showed the pupillary and oculomotor abnormalities in patients with MSA. Quantitative pupillary test may be a potential tool to evaluate the dysautonomia of MSA that reflect the severity of the disease.

References: 1. Armstrong RA. Visual signs and symptoms of multiple system atrophy. Clin Exp Optom 2014; 97:483–491. 2. Anderson T, Luxon L, Quinn N, Daniel S, Marsden CD, Bronstein A. Oculomotor function in multiple system atrophy: clinical and laboratory features in 30 patients. Move Disord 2008; 23: 977–984.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/pupillary-autonomic-dysfunction-and-oculomotor-characteristics-of-multiple-system-atrophy/