Presentation
Presented with right elbow pain and reduced right finger movements for the last 2 months. Nerve conduction study revealed radial neuropathy. Referred for ultrasound tracing of the radial nerve and its branches.
Patient Data
Radial nerve was traced from proximal arm to its bifurcation. Anterior branch was traced up to the wrist. Posterior branch was traced up to mid-forearm. Nerve could not be traced distally to this.
There is a well-defined, encapsulated lesion elevating proximal part of the posterior interosseous nerve meaning there is a lesion deep to the nerve. The lesion is solid, iso to hypoechoic to adjacent to muscles with linear internal strands. There is no calcification / cystic changes / vascularity in the lesion. Approximate size of the lesion is about 29 x 26 x 18 mm. With elbow flexion-extension, the lesion is deformable. Lesion the abutts part of the radial cortex.
The radial nerve is separate from the lesion. Lesion abutts proximal part of the anterior branch of radial nerve without displacing it. The posterior interosseous nerve is hypoechoic, thickened due to compression by this lesion. The nerve is affected from its origin to proximal forearm level. Radial nerve and anterior interosseous nerve show normal echo-pattern.
Extensor muscles in mid forearm show moderate diffuse fatty infiltration and mild volume loss as compared to asymptomatic left side.
There is a well-defined, oblong radiolucency just lateral to the proximal end of the radius in anteroposterior view. Lesion measures about 26 x 13 mm. Bones show normal cortex and trabeculations. There is no fracture / dislocation / bony lesion.
Intraoperative photo shows lipoma deep to the nerve. The 2nd photo is gross specimen of lipoma.
Case Discussion
Findings favor posterior interosseous neuropathy due to a lipoma. Intra-operative and gross specimen photos courtesy operating surgeon Dr Pradip Atodaria.