Congenital arteriovenous malformation of the scalp with a drainage to the transverse sinus: a case report]

Arteriovenous malformation (AVM) of the scalp is uncommon, and a subtype which has connection with the intracranial dural sinus is extremely rare. Only 3 cases have been reported. We present a case of congenital AVM of the scalp which was connected with the intracranial venous sinus. A 27-year-old woman had been noted as having a pulsatile soft mass in the midline of the occipital region since her birth. She visited our hospital because of pain and enlargement of the mass. The patient had had no history of trauma. Physical examination revealed a pulsatile scalp mass in the midline of the occipital region, measuring 3.5 x 3.5 x 1 cm. A loud bruit was ausculated. Tenderness was noted. The skin over the mass was slightly reddish. No focal neurological deficits were noted. Plain skull films demonstrated a round defect in the midline of the occipital bone. Magnetic resonance imaging (MRI) demonstrated a subcutaneous mass with low signal intensity and an infratentorial mass with flow void. 3D CT angiograms demonstrated a subcutaneous vascular mass with a single large vein draining into the right transverse sinus. External carotid angiograms revealed a vascular lesion within the scalp with supply from the branches of the bilateral occipital arteries and the meningeal arteries. The nidus penetrated the skull and connected to a dilated varix, which had a draining vein shunting into the right transverse sinus. After embolization of the right meningeal feeding arteries, surgery was performed. The vascular lesion penetrated the skull and the dura. The infratentorial mass was in the epiarachnoid space and was fed by a small pial artery. The mass was excised completely after interruption of the pial artery and the draining vein. Postoperative course was uneventful. Histologically, the subcutaneous mass and infratentorial vascular mass were shown to be AVM and varix, respectively.