Pathophysiology
Clinical meaning
Cauda equina syndrome (CES) is a surgical emergency caused by compression of the cauda equina, the bundle of lumbar and sacral nerve roots that descend below the termination of the spinal cord (conus medullaris) at approximately the L1-L2 vertebral level. The term 'cauda equina' (Latin for 'horse's tail') describes the appearance of these nerve roots as they fan out within the lumbar cistern, suspended in cerebrospinal fluid within the thecal sac. The cauda equina includes the nerve roots from L2 through S5 and the coccygeal nerve, which innervate the lower extremities, perineum, bladder, bowel, and sexual organs. Compression of these nerve roots produces a characteristic clinical syndrome of bilateral lower extremity weakness, saddle anesthesia (loss of sensation in the perineal, perianal, and medial thigh regions corresponding to the S2-S5 dermatomes), bladder dysfunction (typically urinary retention with overflow incontinence), bowel dysfunction (decreased rectal tone and fecal incontinence), and sexual dysfunction. Understanding the anatomy of the cauda equina is essential for appreciating the pathophysiology. The spinal cord in adults terminates at the conus medullaris, typically at the L1-L2 vertebral level (though this...