Pupillary disturbances in multiple sclerosis: correlation with MRI findings

Area of Science:

• Neuroscience
• Autonomic Nervous System Research
• Multiple Sclerosis (MS) Pathophysiology

Background:

• Pupillary abnormalities, a type of autonomic nervous system disturbance, are infrequently studied in multiple sclerosis (MS).
• Despite limited research, pupillary impairment is observed in MS patients, with its underlying cause remaining unclear.
• Investigating pupillary function offers potential insights into MS neurological damage.

Purpose of the Study:

• To investigate the prevalence and characteristics of pupillary disturbances in MS patients.
• To correlate pupillary defects with magnetic resonance imaging (MRI) findings in the brainstem and spinal cord.
• To elucidate the relationship between pupillary dysfunction and MS-related neurological changes.

Main Methods:

• Prospective study involving 45 MS patients and 30 healthy controls.
• Pupillometry was used to record pupillary contraction latency and amplitude.
• Direct and consensual pupillary reflexes were compared to identify afferent and efferent pathway defects.
• Brainstem and spinal cord MRI evaluated demyelinating lesions and spinal cord cross-sectional area.

Main Results:

• Significant pupillometric impairment was found in 60% of MS patients, compared to none of the controls.
• No correlation was observed between pupillary defects and demyelinating lesions on MRI.
• Efferent pathway abnormalities were the most frequent finding, correlating significantly with spinal cord atrophy (P<0.02).

Conclusions:

• Autonomic nervous system dysfunction, particularly affecting pupillary function, is frequent in MS.
• The parasympathetic system is commonly affected, likely due to axonal loss indicated by spinal cord atrophy.
• Spinal cord atrophy, rather than demyelinating lesions, appears to be the primary correlate of pupillary dysfunction in MS.