Quantitative Evaluation of Cerebellar Function in Multiple System Atrophy with Transcranial Magnetic Stimulation

Area of Science:

• Neuroscience
• Neurology
• Clinical Neurophysiology

Background:

• Objective assessment of cerebellar dysfunction in neurodegenerative diseases is challenging due to overlapping symptoms.
• Cerebellar inhibition (CBI) via dual-coil transcranial magnetic stimulation (TMS) shows promise for evaluating cerebellar function.
• CBI measures the inhibitory effect of cerebellar stimulation on the primary motor cortex (M1), reflected in motor evoked potentials (MEPs).

Purpose of the Study:

• To quantify cerebellar dysfunction in cerebellar type multiple system atrophy (MSA-C) using CBI.
• To compare CBI measurements between MSA-C patients and healthy volunteers.
• To assess the correlation between CBI and the International Cooperative Ataxia Scale Rating (ICARS) in MSA-C patients.

Main Methods:

• Cerebellar inhibition (CBI) was measured by stimulating the hand motor area of M1 and assessing the decrease in MEP amplitude with concurrent cerebellar stimulation.
• The reduction in MEP amplitude under cerebellar stimulation compared to M1 stimulation alone quantified the amount of CBI.
• CBI values from MSA-C patients were compared to those from healthy controls, and correlated with ICARS scores.

Main Results:

• Healthy volunteers exhibited significantly greater cerebellar inhibition than MSA-C patients.
• A significant correlation was found between the amount of CBI and the ICARS score in MSA-C patients, indicating a link between reduced inhibition and ataxia severity.
• These findings highlight the potential of CBI as a quantitative measure in MSA-C.

Conclusions:

• Cerebellar inhibition (CBI) is a viable method for assessing cerebellar dysfunction in MSA-C.
• CBI serves as a potential biomarker for tracking disease progression in multiple system atrophy.
• This technique offers objective insights into cerebellar involvement in neurodegenerative disorders.