A 49-year-old man was admitted to the Neurosurgery Department in our hospital a few hours after experiencing sudden severe dizziness and mental deterioration. He denied any history of hypertension or diabetes. His family and medical histories were non-contributory. On neurological examination, he was drowsy but had no focal neurological deficits. A non-contrast-enhanced computed tomography (CT) head scan showed diffuse subarachnoid hemorrhages (SAHs) in the basal cisterns and large intraventricular hemorrhages (IVHs) throughout the ventricles (Fig. 1A). The ventricles were also enlarged. Three-dimensional CT angiography and conventional cerebral angiography showed an AVM in the left lower frontal region, which was supplied by the left frontopolar artery and drained by the ventricular vein to the sigmoid sinus via the straight and transverse sinuses (Fig. 1B and Fig. 1C). The single drainage vein showed severe ectasia, tortuosity, and a varix, which was suspected to have ruptured (Fig. 1C).

First, we performed extraventricular drainage to relieve the acute hydrocephalus. As the angiography revealed a single feeder (left frontopolar artery) with a diameter of about 3 mm, we planned to perform balloon-assisted Onyx embolization. We performed AVM embolization using 2.8 mL of Onyx assisted by the Scepter XC balloon (Microvention, Inc., Tustin, California, USA) of 4 × 10 mm in size. The duration of the procedure was 20 minutes and it was successful, i.e. the nidus of the AVM was totally occluded (Fig. 2). After the procedure, the patient was managed conservatively. Three weeks after the hemorrhages, the patient showed mild memory impairment and was referred to the rehabilitation department. At two months after the hemorrhages, a non-contrast-enhanced CT head scan showed no abnormal findings (Fig. 3A) and the patient showed signs of improvement in memory. Seven months after the hemorrhages cerebral angiography revealed that the AVM nidus remained totally occluded (Fig. 3B).

A 37-year-old man was admitted to the neurosurgery department in our hospital a few hours after experiencing sudden syncope. He denied any history of hypertension or diabetes. His family and medical histories were non-contributory. On neurological examination, he was alert and did not show any focal neurological deficits. A non-contrast-enhanced CT head scan showed mild hyperdense lesions at the right medial frontal base (Fig. 4A). Brain magnetic resonance imaging (MRI) and angiography (MRA) and conventional cerebral angiography showed an AVM at the right frontal pole, which was supplied by the right medial orbitofrontal and frontopolar arteries and drained by the superficial cerebral vein to the superior sagittal sinus (Fig. 4B, C).

As the angiography revealed that the diameter of the feeder vessel was about 2 mm, we planned to perform balloon-assisted Onyx embolization. One of the feeder vessels, the right medial orbitofrontal artery, was very tortuous (Fig. 5A); the exchange technique was therefore used. This involved the introduction of a 45-degree preshaped Echelon 010 microcatheter into the right medial orbitofrontal artery close to the AVM nidus. A Transcend 014 300 cm microwire was inserted into the Echelon 010 microcatheter and the Echelon microcatheter was withdrawn, leaving the Transcend microwire in situ. The Scepter XC balloon was then introduced into the right medial orbitofrontal artery along the Transcend 014 300 cm microwire. Endovascular embolization of the right medial orbitofrontal artery was performed using 2.8 mL of Onyx assisted by the Scepter XC balloon (4 × 10 mm). The duration of the procedure was 30 minutes and it was successful, i.e. the lower two thirds of the AVM nidus was occluded (Fig. 5A). Angiography of the right frontopolar artery revealed that the upper one third of the AVM remained, and that the artery was also very tortuous. (Fig. 5A). We used the same equipment and exchange technique, with which the Scepter XC balloon was introduced into the right frontopolar artery at the region close to the residual AVM nidus. Endovascular embolization of this artery was performed using 1.3 ml of Onyx assisted by the Scepter XC balloon (4 × 10 mm). The procedure lasted 15 minutes and was successful with the nidus of AVM being totally occluded (Fig. 5B). After the procedure, the patient was managed conservatively and was discharged uneventfully several days later.