[Pure motor neuropathy after radiation therapy: 6 cases]

We report clinical and neurophysiological characteristics of six patients (five women and one man) presenting a pure motor bilateral asymmetric proximal and distal weakness in the setting of radiation therapy for Hodgkin's lymphoma in four cases, carcinoma of the uterus in one, and cancer of the ovary in one. Motor deficit, amyotrophy, cramps, fasciculations and tendinous areflexia were confined to the lower limbs in five patients and to the upper limbs in one. No sensory or sphincter disturbance was noted. The progression of the disease was slow with sometimes secondary stabilization. In some patients, CSF showed a slight increase in protein content with no cell. Blood and MRI medullary examination were normal. Delay between radiation therapy and onset of neurological symptoms range from 6 to 24 years (mean 15). Neurophysiological findings suggest ventral roots proximal conduction blocks. We found an increase F-waves latency, a complete distal palsy contrasting with persistent muscle action potential after distal stimulation, in most of the patients; and an evidence of a conduction block between the erb point and the cervical roots using magnetic stimulation in the patient with upper limbs involvement. Mechanisms and sites of nerve radiation injury remains still unclear. These data could indicate, as it was already reported, a proximal damage involving predominantly the motor roots.