Presentation
Narrowing of the anterior fontanelle was clinically noted during a routine visit to the pediatrics clinic.
Patient Data
A small well-defined low-density (9 HU) scalp lesion is seen at the left posterior parietal region overlying the left lambdoid suture with no detected intracranial extension. There is associated scalloping of the outer table of the underlying parietal bone (which appears as a bony depression on 3D VR images (arrows)).
Narrow anterior fontanelle.
Closed posterior fontanelle.
Normal patent skull sutures.
Normal both cerebral hemispheres, brain stem and cerebellum.
Normal ventricular system and subarachnoid CSF spaces.
A small well-defined oval-shaped hypoechoic scalp lesion is seen at the left posterior parietal region corresponding to the lesion detected on CT images with underlying bone scalloping and a small bone defect, 1.5 mm (representing the lambdoid suture). No detected intracranial extension. Doppler scan revealed no internal vascularity with color flow detected within the underlying left sigmoid sinus.
Case Discussion
This lesion was discovered incidentally during a CT examination and it was clinically palpable during the ultrasound examination. Radiological findings are suggestive of a subgaleal congenital dermoid inclusion cyst.
Congenital dermoid cysts are benign, slow-growing, soft swelling, and non-tender lesions usually seen in the midline structure of the brain 1. The subgaleal location of the dermoid cyst is extremely uncommon 2. There have been very few reports of congenital dermoid cysts arising in the coronal suture 1. We similarly suggested this case be a subgaleal dermoid cyst related to the lambdoid suture. However, a number of cystic lesions including sebaceous cyst, lipoma, hemangioma, subgaleal hematoma, lymphangioma, sinus pericranii, and abscess are considered in the differential diagnosis.
The presence of scalloping involving the outer table of the cranium in X-ray & CT examinations is a characteristic finding of congenital dermoid cyst. It can help to differentiate intracranial extension from the extracranial location of the lesion 3,4.
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