Recurrent Bacterial Meningitis in an Infant Caused by a Sacral Dermal Sinus Tract

Congenital dermal sinus tract is a rare form of closed neural tube defect, connecting the epidermis to a deeper layer. It presents in only one in 2,500 live births. This connection between the outside world and the spinal cord is a nidus for bacterial meningitis and other infections, and dedicated imaging is essential in identifying such a tract. We present a case of a 9-month-old previously healthy male who repeatedly presented with intermittent fevers despite recurrent antibiotics. Cerebrospinal fluid (CSF) analysis consistently demonstrated neutrophilic pleocytosis, elevated protein, and hypoglycorrhachia, while extensive testing for autoimmune etiologies of fever was normal. Whole-body magnetic resonance imaging (MRI) and head computed tomography were negative. He developed an altered mental status, and CSF continued to suggest bacterial meningitis; CSF cultures grew Propionibacterium acnes. Imaging showed hydrocephalus, and an external ventricular drain was placed. A dedicated MRI of the brain and spine was obtained, revealing debris in the lateral ventricles, ventriculitis, leptomeningitis, and a sacral dermal sinus tract with an associated intradural cyst extending from L5-S4. This finding was correlated with a small midline sacral dimple. The patient underwent correction of the dermal sinus tract and removal of the cyst. He improved with ceftriaxone and metronidazole along with placement of a ventriculoperitoneal shunt. This case underscores the importance of a thorough and repeatedly performed physical exam in infants with a history of recurrent fever without a known source. In a patient with recurrent bacterial meningitis, the cause is likely anatomical, and detailed imaging, notably a dedicated spine MRI in this case, is indicated to fully investigate the source even when whole-body MRI demonstrates no abnormal findings.