Further characterization of autonomic involvement in multiple system atrophy: a pupillometric study

Pupillometry is a simple non-invasive technique which allows early detection of an altered functioning of both branches of the Autonomic Nervous System (ANS). In the present study, the pupillometric findings (dark and light diameters and light reflex) obtained in 14 Multiple System Atrophy (MSA) patients (5 with the striatonigral degeneration (SND) type and 9 with the olivopontocerebellar (OPCA) type were compared with those of a sex- and age-matched control group and with a group patients suffering from idiopathic parkinsonism who had never undergone treatment previously. MSA patients showed larger pupils after dark and light adaptation, high degrees of anisocoria after light adaptation and a complex impairment of pupil response to light (mainly occurring in the OPCA-type of MSA) represented by an increase in latency, contraction time and a reduction in contraction amplitude. These data point to the existence in MSA (particularly of OPCA-type) of a pupillary imbalance, mainly involving the parasympathetic branch of the ANS, which is likely to be due to an impairment of the central pathways subserving pupil response to light and is probably detectable in the early stages of the disease by means of dynamic pupillometric evaluation.