gms | German Medical Science

Objective: Amyloidosis is a very rare and mostly systemic disease. A disorder in protein folding leads to dysfunction of concerned organs or nerves. Clinical manifestations can be very different, so it often takes years to final diagnosis. There are only a few reported cases with isolated manifestation of a single peripheral nerve by amyloidoma.We are illustrating two cases treated in our institution (from 2011 to 2013).

Methods: Case guided retrospective analysis of two patients with isolated amyloidoma of a peripheral nerve. Illustration of the special imaging characteristics (MRN and ultrasound) and treatment aspects (in consideration of intraoperative electrophysiology and ultrasound). Follow up time was 54 and 72 months, respectively.

Results: Both of the patients were female, with deep branch lesions of the peroneal and the ulnar nerve. Surgery was performed routinely after preoperative MRN, and pre- as well as intraoperative high-resolution ultrasound. Intraoperative ultrasound depicted thickened and hypoechoic fascicles of the affected nerves. In one patient, preoperative MRN showed a long-segment partly cystic partly solid soft-tissue proliferation in the course of the ulnar nerve. Electrophysiological examination was suspicious of a nerve compression syndrome in both cases. A biopsy of one conspicuous fascicle was performed in both patients. The patient with affection of the ulnar nerve underwent a neurolysis and volar transposition. Immunohistochemical examination of the bioptates resulted in lambda light chain amyloidosis. A systemic manifestation could be excluded by further examinations. Preexisting motor deficits remained unchanged, with a reduction in pain in the patient with affection of the ulnar nerve.

Conclusion: Little is known about the long-term course of this rare pathology. If peripheral nerves are affected by amyloidosis, besides clinical examination and electrophysiological testing, a biopsy of one suspicious fascicle is essential to confirm the diagnosis. Magnetic resonance neurography and neurosonography are helpful complementary tools, but due to the few reported cases in literature, there are no specific morphologic criteria for peripheral nerve amyloidoma.