Late radiation injury to peripheral nerves

Although the peripheral nerve has often been considered as radioresistant, clinical practice demonstrates the occurrence of radiation-induced peripheral neuropathies. Because these complications appear late, usually several years after the course of radiotherapy, their occurrence is explained by improvement in the prognosis of several cancers. Their physiopathology is not fully understood. Compression by radio-induced fibrosis probably plays a central role but direct injury to nerves and blood vessels is probably also involved. The most frequent and best known form of postradiation neuropathy is brachial plexopathy, which may follow irradiation for breast cancer. Recent reports demonstrate that postradiation neuropathies show a great heterogeneity, particularly in the anatomical sites, but also in the clinical, electrophysiological, and neuroimaging features. The link with radiotherapy may be difficult for the clinician to establish. Patients with radiation-induced lumbosacral radiculoplexopathy may be misdiagnosed with amyotrophic lateral sclerosis as they often present with pure lower motor neuron syndrome, or with leptomeningeal metastases since nodular MRI enhancement of the nerve roots of the cauda equina and increased CSF protein content can be observed. From a pathophysiological perspective, radiation-induced neuropathy offers an interesting model for deciphering the mechanisms of peripheral neuropathies due to environmental factors. Recent developments show promising strategies for the prevention and treatment of these complications, which have a considerable impact on a patient's quality of life.