Sunday, September 6, 2009

Extensor Digitorum Brevis Muscle Edema

A 32 year-old male suffered an MVA 3 months ago, and was sent for an ankle MRI due to persistent ankle pain.

(A) Oblique coronal T1-weighted and (B) Oblique coronal T2 fatsat images at slightly different slice positions reveal mild atrophy and striking edema within the extensor digitorum brevis (EDB) muscle.

The traumatic event was three months ago, and it would be unusual for muscle edema to persist this long after an injury. After digging into the clinical history a little further, it came to light that the patient had suffered an injury to his common peroneal nerve at the level of the fibular head, due to a motor vehicle accident.

Thus, the atrophy and edema of the EDB muscle in this case is due to denervation. The differential diagnosis for intramuscular edema is quite broad, and includes trauma, infection, myositis of various etiologies, and systemic diseases such as dermatomyositis.

The most common cause of
extensor digitorum brevis muscle edema is trauma. In the proper clinical context, one should also consider the possibility of anterior tarsal tunnel syndrome. In this disorder, the deep peroneal nerve is trapped/compressed as it travels under the extensor retinaculum. Patients complain of dorsal foot pain. Examination will reveal a sensory deficit in the area between the first and second toes and paresis and atrophy of the extensor digitorum brevis. This syndrome is further discussed in a beautiful review of foot and ankle entrapment by Delfaut et al. (Radiographics 23:613, 2003).

Vic David MD