Accessory head of flexor pollicis longus and its significance in anterior interosseus nerve neuropathies and precision handling

During routine cadaveric dissection of the volar surface of the forearm of a South Indian female of 65 years, we came across a variant of occasional/accessory head of the flexor pollicis longus muscle. It was seen bilaterally arising from the deep surface of the flexor digitorum superficialis. It terminated by inserting into the principle (middle one-third) tendon of flexor pollicis longus. Its clinical significance in the formation of anterior interosseus nerve neuropathies and its probable significance in the loss of precision handling are discussed in detail. The usage of non-invasive methods such as cross sectional imaging techniques to detect the presence of such accessory heads of flexor pollicis muscle is also discussed.