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GS🖐️ Recurrent motor branch of the median nerve
It arises from the median nerve at or distal to the carpal tunnel, with a highly variable origin: it may be extraligamentous, subligamentous, or transligamentous (passing through the flexor retinaculum).
In the palm, the branch courses toward the thenar eminence and becomes superficial as it curves around the superficial head of the flexor pollicis brevis.
On ultrasound, its origin can usually be identified approximately at the level where the proper palmar digital nerves to the thumb arise: once these digital branches are recognized, a third branch may be seen coursing proximally and radially, becoming superficial and skirting the superficial head of the flexor pollicis brevis. This corresponds to the recurrent motor branch.
At this level, it follows a very superficial course, making it particularly vulnerable to traumatic or iatrogenic injury, especially during carpal tunnel release.
⚠️ It is essential to recognize its anatomy and variants, as they are common.
The transligamentous variant, in which the branch passes through the flexor retinaculum, carries the highest surgical risk.
🎯 Function: innervates the thenar muscles responsible for thumb opposition.
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