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Posterior interosseous neuropathy secondary to lipoma

Case contributed by Maulik S Patel
Diagnosis almost certain

Presentation

Right thumb and index finger drop - few weeks. No trauma.

Patient Data

Age: 45
Gender: Female

A well-defined, lobulated, mildly compressible lesion in the proximal radial side of the forearm measuring about 54 x 22 x 20 mm. It is hyperechoic with linear strands without calcification/ cystic changes/ vascularity. It is deep to the brachioradialis and superficial to the supinator. The lesion is deep to the proximal ends of the posterior interosseous nerve and the anterior sensory nerve. The posterior interosseous nerve shows a kink and focal thickening proximal to the supinator.

No mass effect on the superficial sensory branch by the lesion. Forearm extensor muscles show moderate diffuse fatty infiltration and mild volume loss.

Asymptomatic side posterior interosseous nerve shows normal course and size along with normal forearm extensors muscles bulk and echopattern.

The posterior interosseous nerve and the lipoma are outlined.

Well-defined, lobulated fat density over radiocapitellar joint and lateral to the proximal radius. No bony abnormality.

Case Discussion

A female had right proximal-radial forearm pain for the last few months. She developed right-hand index finger and thumb drop in the previous month. A nerve conduction velocity study showed posterior interosseous neuropathy. Ultrasound was requested to trace the nerve and to look for compression. The nerve was compressed by a soft tissue lipoma. X-rays were done later to check the bones and to have a more conventional image of the lipoma.

The nerve conduction velocity study was reported by neuro-physician Dr. Roshan Patel.

A companian case with a surgical follow-up: https://doi.org/10.53347/rID-63343,

 

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