Cerebral microarteriovenous malformations: a series of 28 cases.

OBJECT: Microarteriovenous malformations (micro-AVMs) are a rare subgroup of brain AVMs characterized by a nidus smaller than 1 cm. The authors' purpose in this study was to assess the clinical presentation, radiological features, therapeutic management, and outcome of these lesions.
METHODS: All angiography studies performed at the authors' institution since 2000 for the diagnosis of AVM were retrospectively reviewed. Clinicoradiological findings, therapeutic management, and outcome were evaluated.
RESULTS: Twenty-eight patients had presented with AVMs having a nidus diameter smaller than 1 cm or no clearly identifiable nidus but an early draining vein. All patients, except 2, presented with intracranial hemorrhage, and 12 patients had a focal deficit. Supratentorial hematomas were large (mean volume 25 ml), and in 8 patients hematomas were evacuated urgently. In 6 patients cerebral digital subtraction angiography studies were normal. Magnetic resonance imaging and dynamic MR angiography revealed an AVM in 4 of these 6 patients. Treatment of the AVM consisted of surgery in 16 cases, radiosurgery in 6, and endovascular embolization in 2, and there were no posttreatment deficits. Four patients received no treatment because of their poor condition. The AVM was occluded at the follow-up in all patients treated with surgery or embolization and in 4 of the 6 patients treated with radiosurgery. The Glasgow Outcome Scale (GOS) score was good (GOS 4-5) in 23 patients (82%) and poor (GOS 3-2) in 5 (18%).
CONCLUSIONS: Patients with micro-AVMs generally present with large intracranial hemorrhages and neurological deficits. If the initial angiography is negative, then delayed or superselective angiography is recommended. Magnetic resonance imaging may reveal the existence of these lesions. Surgery is the treatment of choice for superficial micro-AVMs, and radiosurgery or embolization can be considered for deep lesions.