Asterixis: one type of negative myoclonus

Area of Science:

• Neurology
• Neuroscience
• Motor Control Disorders

Background:

• Asterixis is a motor control disorder characterized by irregular, involuntary lapses of posture.
• These lapses are linked to brief silent periods in tonically active muscles.
• Causes can range from metabolic encephalopathies to focal central nervous system (CNS) lesions.

Purpose of the Study:

• To explore the underlying pathophysiological mechanisms of asterixis.
• To differentiate between generalized and focal causes of asterixis.
• To investigate the neural systems involved in sustained muscle contraction and their disruption in asterixis.

Main Methods:

• Analysis of clinical observations and clinicoanatomic correlations.
• Review of literature on metabolic encephalopathies and focal CNS lesions causing asterixis.
• Discussion of potential neurochemical and neurophysiological underpinnings.

Main Results:

• Bilateral asterixis is typically associated with metabolic encephalopathy, while unilateral asterixis suggests a contralateral cerebral hemisphere lesion.
• The dysfunction involves neural circuits for maintaining tonic muscle contraction.
• Asterixis can be triggered by specific CNS lesions (e.g., ventrolateral thalamus) or generalized neurochemical imbalances.

Conclusions:

• Asterixis is not a nonspecific result of CNS disorders but points to specific, albeit not fully elucidated, neural systems.
• Understanding asterixis offers insights into the mechanisms of sustained muscle contraction.
• Further research is needed to define the precise anatomy, neurochemistry, and physiology of the asterixogenic system.