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JAMA Diagnostic Test Interpretation
January 19, 2016

Electrodiagnostic Tests in Polyneuropathy and Radiculopathy

Author Affiliations
  • 1Department of Neurology, University of Michigan, Ann Arbor
JAMA. 2016;315(3):297-298. doi:10.1001/jama.2015.16832

A 66-year-old man with a history of mild diabetes (2 years), coronary artery disease, and gout presented to the neuromuscular clinic with tingling and weakness in his legs. He first noted tingling in his feet 2 to 3 years ago, which slowly progressed to involve his whole foot with numbness that spread up to his knees. Over the same time, he noted trouble with his balance and described that he was “standing on a cushion.” He had low back pain over several years but beginning 1 year ago, he started to hunch over all the time as the result of increasing back pain. He was only able to walk 180 to 270 m before back and leg pain became limiting. Standing did not relieve the pain but sitting did. If he walked for a few minutes, he felt like he ran a marathon with extreme muscle fatigue. He also experienced occasional warm numbness down both legs (left worse than right and sometimes radiating down the back of his legs and other times into his groin). A neurologic examination revealed strength (R/L) 4+/4 dorsiflexion, 5/4+ plantar flexion, otherwise 5/5 throughout. Vibration sensation was (R/L) 0/2 seconds at the toes, and pinprick sensation was decreased to the ankles bilaterally. Reflexes were 2+ throughout with the exception of absent ankle jerks. He was unable to toe or heel walk (worse on the left). Given the diagnostic uncertainty of the localization of nerve injury, electrodiagnostic testing was performed. These tests revealed normal sural sensory responses (Table 1), asymmetric tibial and peroneal motor amplitudes (worse on the left) (Table 2), and active denervation with chronic reinnervation in right L5/S1 innervated muscles including lumbosacral paraspinal muscles.

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