Lateral congenital dermal sinuses extending into the spinal canal: case report and review of the literature.

Lateral congenital dermal sinus (CDS) typically blind-ends in the bone or soft tissue; meanwhile, medial CDS extends into the spinal canal through the spina bifida embryologically. We report the first case of lateral CDS extending into the spinal canal laterally without passing through the spina bifida. A 9-month-old infant presented with infected CDS refractory to partial sinus removal with a combination of surgical drainage and intravenous antibiotics. Eventually, a complete residual sinus removal was performed. Intraoperative findings revealed that the sinus extended into the spinal canal through the intervertebral foramen. This is the first case of lateral CDS extending into the spinal canal through the intervertebral foramen. We proposed a new hypothesis regarding the embryological mechanism of lateral CDS. Preoperative identification of the precise location of CDS is crucial for curable resection of lateral CDS.