Anatomy Msk · Year 1 · from Anatomy Msk
Case 2: Saturday Night Palsy (Radial Nerve Compression)
Clinical Image
Source: Wikimedia Commons - Wrist Drop - CC BY-SA 3.0
Case Presentation
A 35-year-old man presents with inability to extend his right wrist and fingers that he noticed upon waking this morning. He admits to heavy alcohol consumption the night before and recalls falling asleep on a bench with his right arm draped over the backrest. He has no history of trauma. Physical examination reveals weakness of wrist extension (wrist drop), finger extension at the MCP joints, and thumb extension. He can extend his IP joints (medial bands of lumbricals intact). There is weakness of forearm supination with the elbow extended (brachioradialis), but supination with elbow flexed is intact (biceps). Elbow extension (triceps) is normal. Sensation is diminished over the dorsum of the hand and first web space (superficial radial nerve). Finger and thumb flexion are intact, and grip strength is normal. The diagnosis is radial nerve palsy from compression at the spiral groove of the humerus. He is given a wrist extension splint and reassured about the excellent prognosis. At 8-week follow-up, wrist extension has returned to full strength.
Key Learning Points
- The radial nerve (C5-T1) is the largest branch of the posterior cord and winds around the humeral shaft in the spiral groove
- Prolonged compression against a hard surface compresses the nerve in the spiral groove (Saturday night palsy)
- Clinical findings: wrist drop, finger drop, weak thumb extension, sensory loss over dorsal hand (superficial branch)
- Triceps is usually spared because branches exit before the spiral groove
- Finger IP extension is intact due to preserved lumbrical function (ulnar and median nerve)