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Cubital Tunnel Syndrome – NCS Diagnosis — SCE Neurology MCQ

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ModerateClinical NeurophysiologyCubital Tunnel Syndrome – NCS DiagnosisSCE Neurology

A 45-year-old man undergoes nerve conduction studies for suspected ulnar neuropathy. The study shows reduced motor conduction velocity across the elbow segment (below elbow to above elbow) with conduction block at the elbow. Sensory conduction is normal proximal to the elbow but reduced in the digit 5 to wrist segment. What is the diagnosis?

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Correct answer: B — Ulnar neuropathy at the elbow (cubital tunnel syndrome)

Ulnar neuropathy at the elbow (cubital tunnel syndrome) is confirmed by: (1) reduced motor conduction velocity across the elbow segment (focal demyelination), (2) conduction block at the elbow (temporal dispersion/amplitude drop), and (3) reduced sensory conduction in the digit 5 to wrist segment (confirming the ulnar nerve is affected below the site of compression). The most common site is the cubital tunnel (behind the medial epicondyle). A: Guyon canal compression would show abnormalities at/below the wrist only. C: C8/T1 radiculopathy would affect multiple nerves. D: Lower trunk plexopathy would affect ulnar and median C8/T1 territories. E: TOS has different NCS patterns.

Reference: AANEM Ulnar Neuropathy Practice Parameters; ABN NCS Standards