Two occult skull base malformations causing recurrent meningitis in a child: a case report.

Occult malformations of the skull base are rare anomalies, but can cause severe complications such as meningitis. Detailed skull base investigations for detecting cerebrospinal fluid fistulas or celes are often not initiated until after a history of recurrent meningitis. We present a child first seen at the age of 12 with recurrent episodes of bacterial meningitis since early childhood, requiring antibiotic prophylaxis for years. High-resolution computed tomography revealed a chronic sinusitis and a bony defect on the right olfactory groove, while magnetic resonance imaging and CT-cisternography indicated no cerebrospinal fluid fistula or cele at that time. Endonasal surgery for chronic sinusitis was performed with a confirmed bony defect on the right olfactory groove and an olfactory fibre without its sleeve-like dura prolongation running into an adjacent ethmoidal cell, necessitating that it be covered. In the absence of any antibiotics a new episode of meningitis occurred 5 years after surgery. CT-cisternography and magnetic resonance imaging were repeated, now indicating a transclival bony defect with a meningocele in its proximal part, most probably presenting a canalis basilaris medianus. Endonasal surgery confirmed this bony defect after adenoidectomy, and closure was accomplished. No further meningitis has been observed for 2 years. Congenital skull base defects may be difficult to detect, but sufficient surgical closure after their precise delineation is mandatory to prevent infectious endocranial complications. The presence of more than one developmental skull base defect should be considered during careful radiological skull base evaluation, which has to include the clivus in order not to overlook rare basilar malformations.