Cranium bifidum associated with unusual intracranial extension

An atypical, walnut-sized parietal mass was identified in a 9-day-old male. The pregnancy and delivery had been normal. A plain skull X-ray obtained on admission showed a small defect beneath the mass and excessively split sutures, which indicated very high intracranial pressure. A computed tomography (CT) scan revealed a triangular-shaped, low-density area in the falx, extending to the quadrigeminal cistern. Magnetic resonance imaging (MRI) demonstrated a peculiar intracranial extension from the skull defect to the cistern via an intrafalcial sinus-like tract. After excision, it was confirmed by metrizamide CT cisternography that the sinus-like tract was a cerebrospinal cavity. The histological diagnosis was myxofibroma. It was speculated that the mass might have arisen from primitive mesenchymal cells. MRI should be the first diagnostic procedure performed in cases of midline anomalous lesions. (author)