Causes of muscle twitches and spasms
Check out this answer from Consensus:
Muscle twitches and spasms can arise from various neuropathic, spinal, and vascular causes. Understanding the underlying mechanisms is crucial for developing effective treatments. Future research should continue to explore these mechanisms to improve therapeutic strategies and patient outcomes.
By examining the diverse causes of muscle twitches and spasms, we can better appreciate the complexity of these conditions and the importance of targeted interventions.
Muscle twitches and spasms are involuntary contractions that can affect various muscle groups. These phenomena can be caused by a range of underlying conditions, each with distinct pathophysiological mechanisms. This article explores the primary causes of muscle twitches and spasms, drawing on recent research findings.
Neuropathic Causes
Hemimasticatory Spasm
Hemimasticatory spasm is characterized by unilateral spasms of the masticatory muscles, often accompanied by facial hemiatrophy. This condition is believed to result from ectopic activity secondary to focal demyelination of the trigeminal motor nerve fibers. The demyelination may be caused by compression due to deep tissue changes, such as those seen in facial hemiatrophy1.
Brachial Plexus Avulsion
Partial brachial plexus avulsion can lead to pain, involuntary finger twitching, and muscular spasms. The pain and spasms are exacerbated by changes in emotional tone and are thought to be due to a pathological sensory barrage from partially damaged dorsal roots. This barrage activates interneuronal circuits, leading to involuntary movements2.
Spinal Cord Injury
Changes in Motoneuron Excitability
Muscle spasms are common in individuals with chronic spinal cord injury (SCI). These spasms are primarily due to changes in motoneuron excitability and impaired synaptic inhibition, rather than increased synaptic excitation. Current pharmacological treatments that target excitatory inputs may hinder motor recovery, suggesting that future therapies should focus on restoring synaptic inhibition or modulating motoneuron excitability3.
Vascular Compression
Hemifacial Spasm
Hemifacial spasm (HFS) is a form of segmental myoclonus affecting muscles innervated by the facial nerve (CN VII). Primary HFS is often triggered by vascular compression of the facial nerve at the root exit zone, commonly by arteries such as the anterior inferior cerebellar artery. Secondary HFS can result from brainstem tumors, stroke, demyelinating plaques, trauma, or Bell’s palsy. In rare cases, HFS can be associated with developmental venous anomalies, as seen in a case involving a pontine DVA4.