Cauda equina syndrome is a serious condition resulting from dysfunction of the lumbosacral nerve roots and characterized by impairment of bladder, bowel, sexual and lower limb functions. We report the case of a 48-year-old woman who had Crohn's disease for more than twenty years. The patient was undergoing immunotherapy with infliximab and developed a partial cauda equina syndrome after an uneventful minimally invasive microdiscectomy (L₅–S₁) that completely cured her sciatica. A postoperative magnetic resonance imaging examination showed root clumping but no compressive lesion. We discuss a possible relationship between the cauda equina syndrome and the patient's active Crohn's disease, treatment and surgery.