Neurolymphomatosis: MRI and ¹⁸FDG‐PET features

Abstract

Neurolymphomatosis (NL) is a rare presentation of lymphoma or leukemic infiltration of cranial or peripheral nerves. It is distinct from subarachnoid seeding of lymphoma as well as perineural tumour seen in epidural lymphoma. This rare condition has been reported mainly in oncology literature. Imaging features of solitary nerve involvement mimics, among others, peripheral nerve sheath tumours. We present the MRI and (18) fluorodeoxyglucose positron emission tomography ((18) FDG-PET) features of three cases of NL. MRI demonstrated variable appearances: infiltrative mass displacing neural fascicles, diffuse thickening and enhancement, and thickening of individual neural fascicles. (18) FDG-PET demonstrated avid uptake in all cases, two of which revealed skip lesions of the same nerve. The diagnosis of NL was confirmed by uncomplicated CT-guided biopsy of the affected sciatic nerve in one patient.

High-grade B-cell lymphoma relapse presenting as neurolymphomatosis of the median nerve

“…NL on 18 FDG-PET typically shows patchy linear intense 18 FDG uptake along the affected nerve 8. Nerve thickening and skip lesions have also been described 4 9…”

“…Unfortunately, a negative MRI does not exclude NL as the patchy distribution and small size of many lesions in NL reduces the sensitivity for lesion detection 5. Reported MRI imaging features include thickened or nodular nerves and contrast enhancement, however these findings are not specific 9…”

Secondary Neurolymphomatosis of the Radial Nerve: A Diagnostic Challenge

“…NL can involve peripheral or cranial nerves, nerve roots, or nerve plexuses [2]. NL most commonly presents as progressive painful neuropathy or radiculopathy, but the clinical symptoms depend on the involved sites [3]. Diagnosis requires correlation of clinical and imaging findings, and final confirmation by biopsy of the involved structured [4].…”

“…MRI has a reported sensitivity in NL of 77% [3]. It plays an important role due to its panoramicity, multiplanarity, and high resolution for soft tissue, allowing identifying and differentiating between benign and malignant masses.…”

“…The lymphomatous involvement of the nerve sheath typically appears as an infiltrative fusiform lobulated mass enveloping the nerve fascicles, characterized by increased signal on fluid-sensitive sequences, restricted diffusion, and high vascularity. It is associated with slight thickening and hyperemia of the nerve [3]. Although these MRI features suggest the differential diagnosis with more common lipomatous lesions (well circumscribed non-enhancing mass with fat-signal intensity on all sequences), the diagnosis with may be more complex, especially without anamnestic support [6,16].…”