THE POSTIRRADIATION LOWER MOTOR-NEURON SYNDROME - NEURONOPATHY OR RADICULOPATHY

It is not known whether the post-irradiation lower motor neuron syndro me results from radiation damage to motor neuron cell bodies or from d amage to the nerve roots of the cauda equina. We studied six cases who had presented with testicular neoplasms,,subsequently undergoing irra diation that encompassed inter alia para-aortic nodes with co-irradiat ion of the distal spinal cord and cauda equina. A predominantly motor disorder affecting the legs ensued after variable and often prolonged latencies (3-25 years). However all patients also developed mild senso ry features either initially or on prolonged follow-up. Sural sensory nerve action potentials (SNAPs) were normal in five. Mild sphincter sy mptoms occurred in three of five surviving cases after a mean of 7.9 y ears. MRI showed gadolinium enhancement of the cauda equina in two of three patients. The first reported neuropathological study, uncomplica ted by metastatic disease, of the conus and cauda equina was performed in one patient who died. This showed a radiation-induced vasculopathy of the proximal spinal roots, with preservation of motor neuronal cel l bodies and spinal cord architecture. These clinical, radiological, n europhysiological and pathological findings all point to a predominant ly, but not exclusively, motor radiculopathy affecting the irradiated portion of the cauda equina proximal to the dorsal root ganglia. Radia tion exposure exceeded 40 Gy both in our series and in previous report s. The natural history of this disorder is one of relentless deteriora tion occasionally punctuated by 1-2-year periods of stability. Post-ir radiation lumbosacral radiculopathy is a more accurate name for this c ondition.