Delayed radiation-induced motor neuron syndrome: A case report

BACKGROUND: Delayed radiation-induced motor neuron syndrome (DRIMNS) is an atypical motor neuron disorder that develops months or years after radiation therapy. In this study we present a case of DRIMNS that developed forty years after radiotherapy and to discuss differential diagnoses. CASE PRESENTATION: A 56-year-old male patient was admitted to our clinic with complaints of increasing difficulty in walking for the past year. He had a history of operation and radiotherapy due to testicular tumor. Electroneuromyography (ENMG) and thoracic, lumbosacral, plexus and pelvic magnetic resonance imaging (MRI) were performed considering radiculopathy, plexopathy and motor neuron disease in the differential diagnosis. MRIs revealed no abnormality. Needle EMG of lower extremity and lumbar paraspinal muscles revealed fibrillation and positive sharp waves concomitant with fasciculations and reduced recruitment suggesting anterior horn cell/root involvement. DRIMNS was considered rather than motor neuron disease based on the long duration of symptoms with slow progressive course and history of radiotherapy to the pelvic region. CONCLUSION: DRIMNS is a rare entity that should be considered in the differential diagnosis of lower extremity muscle weakness in a patient with a history of malignancy and radiotherapy. EMG findings are very valuable in making the diagnosis together with the clinical picture.