Neurophysiological Features Of Hemiballism

Area of Science:

• Neuroscience
• Movement Disorders
• Electromyography

Background:

• Hemiballism is a rare hyperkinetic movement disorder with poorly understood pathophysiology.
• Limited neurophysiological recordings exist for hemiballism.

Observation:

• Three cases of hemiballism with radiological and neurophysiological findings are presented.
• Acute phase (4-14 days): Irregularly timed, long-duration (200-1500 ms) EMG bursts, asynchronous or alternating in antagonists.
• Subacute phase (6 weeks): EMG bursts (200-1000 ms) became more synchronous or co-contracting as movements shifted to choreiform.

Findings:

• Flailing movements in hemiballism result from prolonged EMG bursts in individual muscles.
• These prolonged bursts are unopposed by antagonist muscle EMG activity.
• EMG activity shifts towards synchrony and co-contraction as hemiballism evolves into choreiform movements.

Implications:

• Provides insights into the neurophysiological mechanisms underlying hemiballism.
• Suggests a dynamic change in motor control patterns during the disorder's progression.
• Highlights the utility of electromyography in characterizing movement disorders.