An unusual case of electromyographic recorded myokymic potentials: a case report

Abnormal spontaneous potentials, specifically myokymia, can occur from various causes. We present the case of a 64-year-old woman with a 12-month history of left leg weakness and difficulty descending stairs. The patients' medical history was significant for breast carcinoma (no node involvement), hypercholesterolemia, and vitamin B(12) deficiency. She previously had a modified radical mastectomy and received chemotherapy (5-flurouracil, methotrexate, Cytoxan [cyclophosphamide]), but received no radiation. She took simvastatin for hypercholesterolemia and received vitamin B(12) injections for her B(12) deficiency. She initially noticed her symptoms when she began taking simvastatin, and they were exacerbated when her dose was increased from 10 to 20mg/d. Electrodiagnostic studies were performed twice at a 6-month interval. Nerve conduction studies were normal, but the initial needle electromyography showed significant myokymic discharges in bilateral iliopsoas, adductor magnus, and left deltoid muscles. The second electromyograph had similar findings, except for the absence of myokymic discharges in the left deltoid muscle. The possible origins of these myokymic discharges are discussed.