[Dermal sinus: a neurosurgical emergency].

Spinal dysraphisms include various types of congenital malformations. About 10% are dermal sinuses, i.e., a connection between the skin elements and intradural space through an open tract. The major complication of this malformation is a central nervous system infection that occurs most frequently before the age of 5 years. We report the case of a lumbosacral skin defect initially described as a coccygeal pit, which happened to be a dermal sinus with a tethered cord after ultrasound imaging in a newborn infant. No indication for surgery was recognized. Later, the infant experienced cerebral empyema and spinal cord edema when he was 5 months old, while a second infection, with a medullar abscess, occurred 7 months later. Both infections began with high fever and were complicated by neurologic deficits. An emergency surgery was performed during the second myelitis. The operative findings confirmed a dermal sinus and a tethered cord. Moreover, they found a dermoid cyst next to the tract. After 2 years of recovery, the child has neurologic deficits including lower limb paraplegia with neurological bladder and bowel. This observation recalls the importance of the differential diagnosis between a coccygeal pit and a dermal sinus, the latter being associated with a dermoid cyst in 50% of cases. Serious neurologic consequences due to the possible infectious complications can occur when a dermal sinus is neglected. A preventive operative excision of both the dermal sinus and a possible cyst is a surgical emergency for spinal dysraphism.