Palmaris longus

Medial epicondyle of humerus (common flexor tendon)

Palmar aponeurosis

Wrist flexor

Median nerve

Ulnar artery

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REVERSED PALMARIS LONGUS

• first reported by Captain John T. Morrison in 1916 as an incidental, post-amputation finding
• variations in Palmaris Longus anatomy are thought to be asymptomatic; however, several authors have described variations of the reversed Palmaris, many of which may cause symptomatic median nerve compression (carpal tunnel-like compression)

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The palmaris longus is a variable muscle, absent in about 16 percent of Caucasians, and less frequently absent in other populations. It may be tendinous above and muscular below; or it may be muscular in the center with a tendon above and below; or it may present two muscular bundles with a central tendon; or finally it may consist solely of a tendinous band.

The muscle may be double.

Slips of origin from the coronoid process or from the radius have been seen.

Partial or complete insertion into the fascia of the forearm, into the tendon of the Flexor carpi ulnaris and pisiform bone, into the scaphoid, and into the muscles of the little finger have been observed.

The Palmaris Longus is one of the most variable muscles and this should consider in surgery of the wrist where good orientation is essential
Recognizing the possibility of atypical variants of Palmaris Longus can be challenging preoperatively
Unless there is very high suspicion of mass effect, most surgeons would not consider imaging studies as part of their diagnostic workup of carpal tunnel syndrome