SCIENTIFIC ARTICLE MRI of pathology-proven peripheral nerve amyloidosis Gavin A. McKenzie 1 & Stephen M. Broski 1 & Benjamin M. Howe 1 & Robert J. Spinner 1 & Kimberly K. Amrami 1 & Angela Dispenzieri 1 & Michael D. Ringler 1 Received: 9 June 2016 /Revised: 29 September 2016 /Accepted: 30 September 2016 # ISS 2016 Abstract Objective To highlight the MRI characteristics of pathologi- cally proven amyloidosis involving the peripheral nervous system (PNS) and determine the utility of MRI in directing targeted biopsy for aiding diagnosis. Materials and methods A retrospective study was performed for patients with pathologically proven PNS amyloidosis who also underwent MRI of the biopsied or excised nerve. MRI signal characteristics, nerve morphology, associated muscular denervation changes, and the presence of multifocal involve- ment were detailed. Pathology reports were reviewed to deter- mine subtypes of amyloid. Charts were reviewed to gather patient demographics, neurological symptoms and radiologist interpretation. Results Four men and three women with a mean age of 62 ± 11 years (range 46–76) were identified. All patients had ab- normal findings on EMG with mixed sensorimotor neuropa- thy. All lesions demonstrated diffuse multifocal neural in- volvement with T1 hypointensity, T2 hyperintensity, and var- iable enhancement on MRI. One lesion exhibited superimposed T2 hypointensity. Six of seven patients demon- strated associated muscular denervation changes. Conclusion Peripheral nerve amyloidosis is rare, and the di- agnosis is difficult because of insidious symptom onset, mixed sensorimotor neurologic deficits, and the potential for a wide variety of nerves affected. On MRI, peripheral nerve involve- ment is most commonly characterized by T1 hypointensity, T2 hyperintensity, variable enhancement, maintenance of the fascicular architecture with fusiform enlargement, multifocal involvement and muscular denervation changes. While this appearance mimics other inflammatory neuropathies, MRI can readily detect neural changes and direct-targeted biopsy, thus facilitating early diagnosis and appropriate management. Keywords Amyloid . Amyloidosis . Peripheral nerve . Amyloidoma . MRI Introduction Amyloidosis refers to a wide spectrum of diseases resulting from extracellular deposits of amyloid protein aggregates that ultimately impair organ function. At present, over 30 different proteins have been identified that can result in amyloid fibril deposition [1]. Amyloidosis occurs in both localized, organ specific or systemic forms, and may be heritable or acquired. Involvement of the peripheral nervous system (PNS) is rare with only a few case reports in the literature [2, 3]. Peripheral neuropathy as a complication of systemic amy- loidosis has been documented in familial amyloid polyneuropathy (FAP), a group of hereditary systemic amy- loidoses with prominent peripheral sensorimotor and auto- nomic involvement, and amyloid light-chain (AL) amyloid- osis, caused by immunoglobulin precursor proteins produced by clonal plasma cells or B-cells. AL amyloidosis is the most common type of acquired amyloid polyneuropathy, with up to 17 % of patients manifesting neurologic symptoms [4]. Amyloid neuropathy most commonly presents as a length- dependent sensorimotor polyneuropathy in patients 40– 70 years of age, with the sensory component preceding the motor component [3, 5]; however, patients may also present with focal mononeuropathy, mononeuropathy multiplex or a radiculoplexopathy with or without autonomic system * Gavin A. McKenzie mckenzie.gavin@mayo.edu 1 Department of Musculoskeletal Radiology, Mayo Clinic, 200 First Street SW, Rochester, MN 55905, USA Skeletal Radiol DOI 10.1007/s00256-016-2510-8