Rare early-onset radiation-induced lumbosacral plexopathy in cervical cancer: a case report.

INTRODUCTION: Radiation-induced lumbosacral plexopathy (RILSP) is a rare and debilitating complication of pelvic radiotherapy, classically presenting months to decades after treatment. Very early onset within weeks is exceedingly rare and may be misattributed to tumor recurrence or other etiologies. We report a case of rare early-onset RILSP that showed a remarkable response to corticosteroid therapy, highlighting crucial diagnostic and therapeutic considerations. CASE PRESENTATION: A 46-year-old cervical cancer patient, who developed symptoms nine weeks after radiotherapy (a total dose of 45 Gy in 25 fractions), including progressive lower limb weakness, difficulty walking, and burning pain in the lower back. An extensive diagnostic workup was performed to exclude other etiologies. High-resolution enhanced MRI of the neuroaxis and a whole-body PET-CT revealed no evidence of tumor recurrence, metastatic compression, or leptomeningeal disease. Cerebrospinal fluid analysis was unremarkable. Furthermore, a comprehensive serological screening for both paraneoplastic antibodies and peripheral neuropathy-associated antibodies returned negative. EMG confirmed acute nerve denervation. Following diagnosis, the patient received monthly five-day courses of methylprednisolone combined with neurotrophic support and rehabilitation, her proximal muscle strength improved from MRC grade 4/5 to 5-/5, and she progressed from being unable to walk unassisted to ambulating over 100 m independently. Clinical improvement remained stable at the 6-month follow-up. CONCLUSION: This case demonstrates that RILSP can occur early after radiotherapy, highlighting the importance of maintaining diagnostic vigilance following treatment. Early detection, thorough exclusion of malignancy, and prompt corticosteroid treatment may take advantage of a potentially reversible inflammatory or vasogenic phase before irreversible fibrotic damage develops.