Brachial plexus lipomatosis

Brachial plexus lipomatosis with perineurial pseudoonion bulb formation: Result of a mosaic PIK3CA gene mutation in the para-axial mesoderm state ¹⁾.

Gaber et al. presented the case of a 56-year-old woman who presented with severe right ulnar distribution pain involving the medial forearm and hand (9/10 on a numerical rating scale), declining right-hand strength, movement-dependent hypoesthesias, paresthesias, and a pronounced claw deformity of the right hand with intrinsic atrophy. Electrodiagnostic studies demonstrated pronounced fibrillations, decreased voluntary activation, and minimal collateral reinnervation in the abductor digiti minimi and abductor pollicis brevis, consistent with dysfunction of the lower trunk of the right brachial plexus. Magnetic resonance imaging (MRI) and computed tomography (CT) of the brachial plexus were interpreted as a tumor on the right supra- and infraclavicular brachial plexus. At surgery, the brachial plexus was embedded in relatively tight connective tissue with a typical lipoma posteriorly. The lipoma was resected, and the plexus was explored extensively. This case is the 10th report of nerve lipomatosis involving the brachial plexus and demonstrated the cardinal features. It provides insight into the pattern of lesions associated with innervation by nerve lipomatosis ²⁾.