Normal Ulnar Sensory Responses with Conduction Block at the Elbow

ABSTRACT.

In the electrodiagnosis of ulnar neuropathy at the elbow, typical findings include abnormal sensory and motor responses on the symptomatic side. We report three cases in which routine ulnar sensory recordings were normal, but motor recordings and “inching technique” illustrated electrophysiologic findings of conduction block at the elbow. Electrodiagnostic technologists should be aware of this presentation. Needle EMG examinations supported the diagnosis of ulnar neuropathy at the elbow (UNE). Inching techniques were performed to localize the lesion to the retroepicondylar groove. The mechanisms for these findings are discussed.

KEY WORDS.:

• Compound motor action potential
• CMAP
• conduction block
• fascicles
• “inching”
• retroepicondylar groove
• sensory nerve action potential
• SNAP