MRI of Conus Medullaris, Cauda Equina, and Filum Terminale Lesions

Abstract

Cauda equina is the Latin name for horse's tail because the cauda equina resembles a horse tail. The cauda equina is a set of 10 paired dorsal and ventral nerve roots (20 nerve roots in total), corresponding to four lumbar (second to fifth), five sacral, and one coccygeal segments that originate from the conus medullaris. These nerve roots are contained by the thecal sac, which is an enclosed space formed by dura mater and arachnoid extending from the head to the sacrum. The conus medullaris is an expansion of the terminating distal thoracic spinal cord, typically located at the T12-L1 level.