The brachioradialis reflex, also called the supinator reflex, is a stretch reflex in which a tap near the wrist makes the brachioradialis contract and the elbow bend. It tests mainly the C6 root and the radial nerve. It complements the biceps reflex in assessing C5-C6.
| Nerve root | C6 (C5-C6) |
|---|---|
| Area | Brachioradialis tendon on the radial side of the forearm, a few centimetres above the radial styloid |
| How to test | With the forearm resting in mid-pronation on the patient's lap, the examiner strikes the distal radial forearm and watches for elbow flexion and supination. |
| Muscles | |
| Nerve Supply | Radial nerve |
Confirms the integrity of the C6 reflex arc and helps localise lesions around C5-C6.
A reduced reflex suggests C6 radiculopathy. The inverted supinator sign, where tapping the tendon produces finger flexion but little or no elbow flexion, suggests a lesion at C5-C6 that damages the root and also compresses the cord below it. Tendon reflexes are graded 0 (absent) to 4+ (clonus), with 2+ normal; symmetry matters more than the absolute grade.
Compression of the C6 root at C5-C6 reduces or abolishes this reflex, usually with thumb numbness and wrist extensor weakness.
Cord compression at C5-C6 can produce the inverted supinator sign, with finger flexion instead of elbow flexion.
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