Hypertrophied palmaris longus muscle

Case contributed by Dr Mustafa Hammad


Male patient, presents with swelling in the volar aspect of his forearm.

Patient Data

Age: 26 years
Gender: Male

There is mass-like lesion  located at the volar aspect of right forearm, which is of muscle signal on all sequences.

This mass located medial to the flexor carpi radialis tendon in the expected anatomic location of the palmaris longus muscle. Just abuts the median nerve.

EMG was performed, which was normal. US was also performed to assess its relationship to median nerve.


Pseudomass hypertrophy of the palmaris longus muscle. The median nerve is extending under the hypertrophied muscle.

NB The arrows show that median nerve located adjacent to this muscle.

Case Discussion

Palmaris longus is a short fusiform muscle, the origin of this muscle is from the medial epicondyle of the humerus and inserts in the wrist at the palmar aponeurosis superficial to the level of the flexor retinaculum.

Variant anatomy is described in the literature and can include anomalous origin, course and/or insertion. Such variants also include duplication, digastric, and entirely muscular or proximal tendinous and distal muscular (i.e. reverse palmaris longus). 

Palmaris longus anomalies can present with median nerve compression symptoms that are indistinguishable from symptoms due to other masses.

The radiologist should be familiar with these anomalies to prevent unneeded surgery.

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Case information

rID: 48369
Published: 16th Oct 2016
Last edited: 16th Jul 2018
Inclusion in quiz mode: Excluded

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