Clinical, Neurophysiologic, and Pathologic Features in Patients With Early Onset Post-Radiation Neuropathy

Objective: To study early-onset radiation-induced neuropathy reviewing neurologic course, steroid-response, and available nerve biopsies.

Methods: Patients coded with radiation-induced neuropathy within six-months of radiation were reviewed from January 1^st,1999-August 31^st, 2022. Patients had to have electrodiagnostically confirmed neuropathy localized within or distal to radiation fields. Neurological course and nerve biopsies were reviewed.

Results: Twenty-eight patients (16 males and 12 females, mean age 63.8 years) were identified. Average radiation dose was 4659cGy (range 1000-7208). Tumor infiltration was not observed on MRI and PET. Post radiation onsets averaged 2 months (range 0-5). Localizations included brachial (n=4) plexopathies, lumbosacral (n=12) plexopathies, radiculopathies (n=10), and mononeuropathies (n=2). Neuropathic pain (n=25) and weakness (n=25) were typical. The clinical courses were subacute monophasic (n=14), chronic progressive (n=8) or static (n=1), and 5 were without follow-up. Nerve biopsies (n=8) showed an inflammatory ischemic process with perivascular inflammatory infiltrates (n=7) or microvasculitis (n=2). Nine patients, 7 with monophasic courses, received steroid burst therapy with symptom improvement in 8. No patients recovered entirely back to baseline.

Discussion: In contrast to chronic radiation induced neuropathy early-onset patients most commonly have painful, monophasic courses with residual deficits, possibly steroid responsive. An ischemic inflammatory pathogenesis is suggested.