Abstract Details

Title Unusual Quivering Muscle

Topic Neuromuscular and Clinical Neurophysiology (EMG)

Presentation(s) P3 - Poster Session 3 (5:30 PM-6:30 PM)

Poster/Presentation
Number 1-001

Objective

This case report discusses myokymia involving the pectoralis muscle from abnormal synkinesis, which is a rare entity.

Background Myokymia presents as wave like involuntary contractions spreading across the muscle surface, resulting from hyperexcitability of peripheral nerve motor axons anywhere along the nerve from the cell body to the neuromuscular junction. It has been previously reported to involve periorbital and perioral muscles with demyelination, focal trauma, radiation induced nerve damage, chronic peripheral nerve disorders, certain toxin exposures, channelopathies etc.

Design/Methods 44-year-old male presented to University of Kentucky Hospital, with radiating neck pain to the right shoulder, associated with increased twitching of right shoulder muscles. He reported remote history of extensive reconstructive plastic surgery on his right upper extremity, after an accident resulting in near amputation of arm, approximately 28 years ago. He noticed involuntary twitching of the right shoulder reconstructed flap, couple of years after initial injury and noticed constant painful twitching for a year, exacerbated with fatigue, cold pain and resolved during sleep. On examination, these movements were involuntary, irregularly rhythmic contractions of right pectoralis major, 1 every 2-3 seconds, and drove his right arm externally. CT C-spine showed severe C6-C7 spinal stenosis with foraminal compression. Electromyography showed motor unit action potentials 4 to 10, multiple single motor unit discharges, firing at irregular or regular intervals, with rates of 5-150 Hz consistent with myokymic discharges involving the right pectoralis major reconstructed flap. He underwent C6-C7 anterior cervical discectomy with fusion for neck pain and reported some improvement in twitching. Medical treatment with carbamazepine and gabapentin failed and treatment with Botulintoxin was declined.

Results In our case, the reconstructive surgical flap led to disruption of the biochemical microenvironment innervating the pectoralis major, abnormal regeneration of peripheral nerves and with synkinesis leading to spontaneous contractions and hyperexcitability.

Conclusions

Video of myokymia and EMG will be displayed.

Authors/Disclosures
Zabeen K. Mahuwala, MD, FAAN (University of Kentucky, KY Clinic Neurology Department) PRESENTER	Dr. Mahuwala has received personal compensation in the range of $500-$4,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Argenx. Dr. Mahuwala has received personal compensation in the range of $500-$4,999 for serving on a Scientific Advisory or Data Safety Monitoring board for academic CME. Dr. Mahuwala has received personal compensation in the range of $500-$4,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Janssen Scientific affairs. Dr. Mahuwala has received personal compensation in the range of $500-$4,999 for serving on a Scientific Advisory or Data Safety Monitoring board for amgen. The institution of Dr. Mahuwala has received research support from UCB, . The institution of Dr. Mahuwala has received research support from Alexion . The institution of Dr. Mahuwala has received research support from argenx . The institution of Dr. Mahuwala has received research support from immunovant.
Laura Bakare, MD (Laura Bakare)	Dr. Bakare has nothing to disclose.

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