Dr Ken Vatz's EMG Question

A 40 year old non-diabetic man, without previous history of entrapment neuropathy, motor neuropathy, known trauma or systemic illness presents with a painless, progressive weakness of the extensors of the fingers and wrist on the right over 2 years. There are no sensory complaints. There is no known family history of neurologic disease. On clinical neurologic examination, there is marked weakness of the finger extensors, moderate to marked weakness of the wrist extensors, apparent weakness of the interossei without atrophy, mild to moderate weakness of the triceps, and normal strength of the brachioradialis. The biceps and brachioradialis reflexes were normoactive and symmetrical bilaterally. The right triceps reflex was trace, with the left triceps reflex being normoactive. The DTR's in the lower extremities were normoactive and symmetrical, and the plantar responses were flexor. No sensory abnormalities were found.

The EMG/NCS data are below.

I would be interested in any thoughts about the precise localization of the lesion in the radial nerve or posterior division of the plexus (or elsewhere) and the etiologic differential diagnosis. I have ordered an x-ray of the humerus and an MRI scan of the upper arm. If these are negative, I plan to order an MRI of the plexus, pending, of course, comments and opinions from list members.

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Revised July 29, 2000

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