Palmaris profundus (also known as ''musculus comitans nervi mediani'' or ''palmaris bitendinous'') is a rare anatomical variant in the anterior compartment of forearm. It was first described in 1908. It is usually found incidentally in cadaveric dissection or surgery.

Structure

Pirola et al. classified the muscle into subtypes depending on its origin: (1) from the

radius In classical geometry, a radius (: radii or radiuses) of a circle or sphere is any of the line segments from its Centre (geometry), center to its perimeter, and in more modern usage, it is also their length. The radius of a regular polygon is th ...

, (2) from the

flexor digitorum superficialis Flexor digitorum superficialis (''flexor digitorum sublimis'') or flexor digitorum communis sublimis is an extrinsic flexor muscle of the fingers at the proximal interphalangeal joints. It is in the anterior compartment of the forearm. It is s ...

fascia, and (3) from the

ulna The ulna or ulnar bone (: ulnae or ulnas) is a long bone in the forearm stretching from the elbow to the wrist. It is on the same side of the forearm as the little finger, running parallel to the Radius (bone), radius, the forearm's other long ...

. Though, other origins of the muscle were reported including the

medial epicondyle of humerus The medial epicondyle of the humerus is an epicondyle of the humerus bone of the upper arm in humans. It is larger and more prominent than the lateral epicondyle and is directed slightly more posteriorly in the anatomical position. In birds, whe ...

, the

palmaris longus The palmaris longus is a muscle visible as a small tendon located between the flexor carpi radialis and the flexor carpi ulnaris, although it is not always present. Reviews report rates of absence in the general population ranging from 10–20%; h ...

and the

flexor pollicis longus The flexor pollicis longus (; FPL, Latin ''flexor'', bender; ''pollicis'', of the thumb; ''longus'', long) is a muscle in the forearm and hand that flexes the thumb. It lies in the same plane as the flexor digitorum profundus. This muscle is uniq ...

. It runs deep to the

pronator teres The pronator teres is a muscle (located mainly in the forearm) that, along with the pronator quadratus, serves to pronate the forearm (turning it so that the palm faces posteriorly when from the anatomical position). It has two origins, at th ...

and lateral to the flexor digitorum superficialis. Its tendon passes beneath the flexor retinaculum through the

carpal tunnel In the human body, the carpal tunnel or carpal canal is a flattened body cavity on the flexor ( palmar/volar) side of the wrist, bounded by the carpal bones and flexor retinaculum. It forms the passageway that transmits the median nerve and the ...

before broadening out to insert to the deep part of

palmar aponeurosis The palmar aponeurosis (palmar fascia) Deep fascia, invests the muscles of the palm, and consists of central, lateral, and medial portions. Structure The central portion occupies the middle of the palm, is triangular in shape, and of great strengt ...

. In many cases, the muscle is contained within the same fascial sheath as the

median nerve The median nerve is a nerve in humans and other animals in the upper limb. It is one of the five main nerves originating from the brachial plexus. The median nerve originates from the lateral and medial cords of the brachial plexus, and has cont ...

. To indicate this association, the term musculus comitans nervi mediani is often used''.'' It can also be referred to as the palmaris bitendinosus when originating from the palmaris longus. It can be considered a variation of the palmaris longus, however, it may exist in addition to the palmaris longus. If both of them coexist, the aberrant palmaris profundus tends to be the deeper one. Nerve supply to the palmaris profundus varies. Innervations by the median nerve, anterior interosseous nerve or the

ulnar nerve The ulnar nerve is a nerve that runs near the ulna, one of the two long bones in the forearm. The ulnar collateral ligament of elbow joint is in relation with the ulnar nerve. The nerve is the largest in the human body unprotected by muscle or ...

were reported. Function of the palmaris profundus is similar to the palmaris longus. It is a flexor of the wrist.

Clinical significance

The presence of the palmaris profundus is often associated with median nerve compression and

carpal tunnel syndrome Carpal tunnel syndrome (CTS) is a nerve compression syndrome associated with the collected signs and symptoms of Pathophysiology of nerve entrapment#Compression, compression of the median nerve at the carpal tunnel in the wrist. Carpal tunn ...

as available space for the median nerve decreases due to the presence of an additional tendon. It may also complicate the surgical release of the carpal tunnel. It may compress the anterior interosseous nerve, a motor branch of the median nerve, causing a condition called anterior interosseous nerve syndrome.

References

{{Muscles_of_upper_limb Muscles of the upper limb Anatomical variations

Structure

Clinical significance

See also

References