Midline dermal sinuses and cysts and their relationship to the central nervous system.

Sixty-one children (below 12 years) with midline dermal inclusions of the cranium and spine were operated on at the Red Cross War Memorial Children's Hospital between 1969-1990. The bregmatic area was the most common position for superficial cysts (33). Eight children had sinuses or cysts near the external occipital protuberance, 2 had isolated fourth ventricular cysts and 1 had a cyst in the quadrigeminal plate cistern. Fifteen children had spinal dermal inclusions, 13 of these were in the lumbosacral area, there was 1 sinus in the cervical spine and another in the midthoracic area attached to an intramedullary cyst. Two children had frontal sinuses, one of which was connected to an interhemispheric dermoid cyst and a lipoma of the corpus callosum. A midline swelling or sinus was the most common clinical presentation. Four out of 15 spinal inclusions and 1/11 occipital sinuses had a meningitic history. Five of 11 of the posterior fossa inclusions had raised intracranial pressure and signs suggestive of cerebellar tumor or abscess. Not one of the 33 bregmatic lesions had any connection to the central nervous system. MRI has proved useful in diagnosing both dermal sinuses and cysts, but CT scanning was our standard investigation. Plain x-ray revealed bony abnormalities in only 60% of our patients with spinal sinuses. We feel that all dermal sinuses or cysts in the midline should be surgically explored after CT or MRI scanning. Lesions mistaken for bregmatic cysts have included hemangiomas (4), hamartomas (2), an encephalocele through the anterior fontanelle (1) and lipomas (2).(ABSTRACT TRUNCATED AT 250 WORDS)