[Spinal neurenteric cyst revealed by a cauda equina syndrome]

Intraspinal neurenteric cysts are exceptional formations which develop from incomplete separation of the neural tube and the endodermis during the third week of gestation. Symptoms generally appear before the age of 40 years and are associated with spinal malformations. Most neurenteric cysts lie in an extra-spinal position in the lower cervical and upper dorsal spine. We report a case involving the cauda equina with no associated spinal lesion.

A 63-year-old woman was admitted for low back pain and right L3 radiculalgia triggered by exertion. Urinary disorders had developed over the preceding year. Physical examination found a spinal syndrome with hypoesthesia of the right para-anal area, an atonic anal sphincter and a globular bladder. Plain films showed a widened interpedicular space between L1 and L2 interpreted as the consequence of an expansive intraspinal lesion. Saccoradiculography led to the diagnosis of an intradural lesion involving L1 and L2. At magnetic resonance imaging, the lesion's signal intensity was similar to cerebrospinal fluid on T1 and T2 sequences, deforming the cauda equina and displacing the nerve roots. Surgical resection of the cyst was incomplete due to adherences to several roots and was followed by persistent radiculalgia and sphincter disorders.

This case demonstrates an exceptional cause of cauda equina syndrome. Fissuration or rupture of the cyst might explain symptom exacerbation following trauma. Magnetic resonance imagining can confirm the cystic nature of the intradural lesion and help guide surgery. Resection is often incomplete with the risk of long-term recurrence.