Lumbosacral plexopathy caused by radiotherapy is a rare but severe consequence of cancer treatment. This condition often leads to varying degrees of sensory and motor impairment. Neurological complications, which are typically permanent, manifest a long period after irradiation.

We describe a case of progressive lower extremity weakness and sensory impairment in a woman who had been effectively treated with radiotherapy for cervical cancer with development 36 years after irradiation. The electrophysiological assessment revealed a subacute bilateral axonal lesion of the lumbosacral plexus. None of the clinical manifestations, serology, cerebrospinal fluid or imaging data discovered an explanation other than radiation-induced lumbosacral plexopathy (RILP).

This case demonstrates that RILP may emerge more than 30 years after the radiotherapy.