Nasal Dermal Sinus Associated with a Dumbbell-Shaped Dermoid: A Case Report

Nasal dermal sinus is a rare congenital anomaly. We report a case of the dermal sinus associated with a dumbbell-shaped dermoid and demonstrate the detailed anatomy. The patient was a boy aged 1 year and 4 months with a small pit at his nasion from birth and developed swelling of the forehead. The sagittal view of a T2-weighted image demonstrated a dumbbell-shaped, mixed intense dermoid at the foramen cecum. The sinus tract was depicted as a strand of isointensity between the dermoid and the nasion. Serial sagittal views of T1-weighted images revealed the capsule of the dermoid enhanced with contrast medium, and that the subcutaneous abscess was in continuity with the dermoid. On diffusion-weighted imaging, both the dermoid and subcutaneous abscess were demonstrated as a hyperintensity. Serial sections of the sagittal and coronal computed tomography scans clearly showed an enlarged fonticulus frontalis and foramen cecum remnant and dehiscence of the crista galli. The purulent dermoid cyst including the capsule and the dermal sinus tract were removed completely. We describe our detailed anatomical relationship between the sinus tract with dumbbell-shaped dermoid and the surrounding structures, and emphasize the importance of these anatomy for operation.