Case report: a case review of Lambert–Eaton myasthenic syndrome and low back pain

The following is a case report which reviews the essential aspects of Lambert–Eaton myasthenic syndrome (LEMS) in a patient with long standing back pain and gait dysfunction. The patient was referred to our electrodiagnostics laboratory for a 9-month history of low back pain and difficulty walking following a charity breast cancer walk. A workup including magnetic resonance imaging of the brain, entire spine, and EMG/NCS at another institution were reportedly normal. A detailed history revealed symptoms of proximal weakness and autonomic dysfunction. Physical findings were consistent with proximal weakness, a bilateral gluteus medius gait, and diffusely absent reflexes obtainable in the biceps after 3 s of contraction. Electrical testing revealed an initial low compound muscle action potential amplitude in the deep peroneal nerve recording from the extensor digitorum brevis. Repetitive stimulation at 2 Hz revealed a decremental response of 42% from the 1st response to the 4th response. Following 3 s of exercise, the amplitude increased by 300%. After 30 s of exercise followed by 1 min of rest, there was a return of the decremental response. The history, physical examination, and electrical findings were illustrative of a presynaptic neuromuscular junction disorder, specifically LEMS.