Unusual cause of incomplete cauda equina syndrome: dermoid cyst with a split cord malformation case report

Abstract Cauda equina syndrome is a surgical emergency caused by the compression of the lumbosacral nerves. The most frequent cause is discal herniation, while tumoral pathology in this region is rare, and congenital processes are less common. We report the case of a young 37-year-old male patient, admitted to the emergency room with an incomplete cauda equina syndrome. As medical history, a lumbar surgery 15 years ago was reported with no documentation. An MRI was performed, revealing a mass within the filum terminal exhibiting three components suggestive of a dermoid cyst accompanying a split cord malformation, which was confirmed by pathology. Various disorders may be associated to intradural dermoid cyst, such as lipoma, low-lying cord, hydromyelia or thick filum. Surgery is the treatment of choice, and MRI plays a crucial role in detecting associated abnormalities and determining surgery priorities.