Compromise of brain tissue caused by cortical venous reflux of intracranial dural arteriovenous fistulas: assessment with diffusion-weighted magnetic resonance imaging.

BACKGROUND AND PURPOSE Cortical venous reflux (CVR) is a high risk factor for aggressive behavior of intracranial dural arteriovenous fistulas (DAVF). The pathological conditions in brain tissue affected by CVR were investigated by diffusion-weighted magnetic resonance imaging. METHODS A retrospective review identified 56 patients with DAVFs who underwent diffusion-weighted imaging before treatment. Twenty patients had neurological symptoms corresponding to the brain area affected by CVR (Group I), 21 patients with CVR had no focal brain dysfunctions (Group II), and 15 patients had no CVR (Group III). Apparent diffusion coefficient (ADC) was measured for 11 brain areas predefined based on normal venous drainage patterns in the 56 patients and in 21 normal volunteers. The mean ADC ratio was calculated for each area by dividing the ADC value of patients by that of normal volunteers. RESULTS Areas affected by CVR in Group I showed a mean ADC-to-control ratio of 0.72, which was significantly lower than that of Group II (0.96, P<0.01). Follow-up studies demonstrated significantly increased ADC ratios in brain areas affected by CVR after the DAVFs were treated successfully. The mean ADC ratio of an affected area remained low, with persistent symptoms in 1 patient who underwent palliative treatment. CONCLUSIONS Decreased ADC was observed in the brain parenchyma affected by CVR and was associated with regional brain dysfunction. Successful treatment of the DAVF increased the ADC toward normal levels. The ADC may be a useful indicator of the severity of CVR.