Treatment of segmental continuous hypertrophic myokymia of the limb with botulinum A toxin

Myokymia is defined as fluctuating hyperexcitability of muscle fibers caused by repetitive spontaneous contraction of motor units. Myokymia is generally benign with self-resolution, although symptomatic treatment with benzodiazepines, anticonvulsants, and muscle relaxants can be used. Botulinum toxins can also be utilized, although they are mostly used for symptomatic facial myokymia. Here, we report two patients who developed continuous myokymia, resulting in secondary hypertrophy, stiffness, and discomfort in the affected muscles. The first patient had a history of a tethered spinal cord and developed continuous myokymia in the S1 and S2 radicular regions of the left leg. The second patient underwent radiation therapy for lung cancer and developed brachial plexopathy with abnormal activity in the muscles supplied by the musculocutaneous nerve in the right arm. Both patients experienced sleep disturbance, focal discomfort, and restlessness. The anticonvulsants and muscle relaxants were ineffective. Chemodenervation with botulinum A toxin was initiated using either onabotulinumtoxinA or abobotulinumtoxinA. Both patients experienced a substantial reduction in myokymia, with ongoing reversal of muscle hypertrophy and significant improvement in reported subjective symptoms. Treatment with botulinum toxins can be highly effective in patients with symptomatic segmental continuous hypertrophic myokymia and may be considered first-line therapy.