The Twitching Trunk: Etiology and Treatment of Truncal Myoclonus

Objective: To discuss truncal myoclonus as a post-stroke movement disorder that can be associated with rare focal status epilepticus. Background: Myoclonus is classified by its source of generation: cortical, subcortical, spinal, or peripheral. Post-stroke movement disorders are typically due to lesions of the basal ganglia and thalamus but only occur 4% of the time. Post-stroke myoclonus is much rarer. Design/Methods: A 55-year-old female with history of right MCA stroke one year prior and subsequent right frontal focal seizures presented with left hand twitching. EEG demonstrated right centro-temporal sharp waves with lateralized periodic discharges. She was started on carbamazepine with resolution of hand twitching and normalization of the EEG, without further epileptiform discharges. However, she developed myoclonic jerks of her abdomen without alteration in consciousness. The myoclonus was present at rest, improved during sleep, and not painful. Brain MRI demonstrated encephalomalacia of old stroke. MRI C-spine, T-spine, and repeat EEG were normal. Carbamazepine was discontinued due to worsening truncal myoclonus. Valproic acid was started with significant improvement. Results: Our patient had features that may mimic other etiologies of truncal myoclonus such as Lance-Adams, diaphragmatic flutter, and propriospinal myoclonus. However, she did not have post-anoxic injury, respiratory symptoms, or spinal abnormalities. The truncal myoclonus was likely secondary to her underlying stroke and therefore cortical. When post-stroke myoclonus persists it may be a rare variant of focal status epilepticus. In the future, electromyography would be useful to confirm specific pathophysiology. Conclusions: The underlying pathology of post-stroke myoclonus is due to dysfunction in GABA inhibitory neurotransmission. It can be challenging to diagnose myoclonus in patients who have concurrent focal epilepsy from underlying stroke. It is most important to determine physiology since this dictates treatment: carbamazepine may worsen myoclonus; clonazepam is effective in all forms of myoclonus; valproic acid and levetiracetam are effective for cortical myoclonus, but not other forms. Disclosure: Dr. Niazi has nothing to disclose. Dr. Frey has nothing to disclose. Dr. Raghavan has nothing to disclose. Dr. Murray has nothing to disclose.