Neuralgic amyotrophy (NA) is an acute immune‐mediated neuropathy with nonspecific symptoms that can mimic traumatic, infectious, tumorous, or degenerative conditions. In these cases, MR neurography is an important diagnostic tool to assess peripheral nerves and rule out differential diagnoses. This case report presents the imaging findings in a 66‐year‐old cachectic woman with suspected NA and illustrates the diagnostic challenge in MR neurography due to signal abnormalities associated with severe cachexia. Initially, the patient presented with new‐onset nocturnal right‐sided shoulder pain unresponsive to analgesics and progressive arm paresis without sensory deficits. Neuromuscular ultrasound revealed an irregular enlargement of the right posterior interosseous nerve, with corresponding muscle denervation in electromyography. Subsequent and repeated MR neurography of the brachial plexus was largely nondiagnostic due to lack of fat suppression on nerve‐selective MR sequences as well as pseudo‐fat saturation appearances on T1‐weighted images, which altogether obscured the plexus and prevented reliable diagnostic evaluation. Although MR neurography plays an increasing role in the diagnosis of peripheral neuropathies, this case highlights its potential limitations and pitfalls in severe cachexia.
Borde et al. (Thu,) studied this question.