What is the role of nerve conduction studies in the evaluation of ulnar neuropathy?

Updated: Jun 08, 2018
  • Author: Charles F Guardia, III, MD; Chief Editor: Nicholas Lorenzo, MD, MHA, CPE  more...
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Answer

Basic sensory and motor nerve parameters measured in nerve conduction studies include latency, amplitude, and conduction velocity. Electrodes (metallic reusable or pregelled disposable tape) are placed over the main belly of the active muscle (eg, the abductor digiti quinti or the first dorsal interosseous muscle) [109] and the tendon of the fifth or first digit. The ulnar nerve is stimulated at the wrist and above and below the elbow; this helps localize the site of involvement.

Short-segment stimulation (also known as the inching technique), in which the nerve is stimulated over 1- to 2-cm intervals, can increase the sensitivity of the procedure and may improve localization by helping the examiner judge whether a blockage is infracondylar (ie, near the cubital tunnel) or higher (ie, near the ulnar or epicondylar groove, the location associated with tardy ulnar palsy). (See the image below.)

Inching technique used to isolate conduction block Inching technique used to isolate conduction block in left ulnar nerve. Note significant amplitude drop at 305 mm, which correlates with position 2 cm above medial epicondyle. This is example of supracondylar block. Image courtesy of A S Lorenzo, MD.

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