A 79-year-old woman arrived at our emergency department because of sudden sensory aphasia that had occurred one hour before. She had no past medical history, was a non-smoker, and did not drink alcohol. Her initial vital signs were blood pressure, 201/99 mmHg; heart rate, 98 bpm; respiratory rate, 18 breaths/min; and body temperature, 36.4°C. Her initial National Institutes of Health Stroke Scale (NIHSS) score was 8. Her symptoms were suspected to be the result of an acute stoke, and IV r-tPA was indicated if her brain computed tomography (CT) revealed no hemorrhagic stroke. In fact, brain CT revealed no abnormalities (Fig. 1A). To exclude stroke mimics, such as convulsion disorder presenting with pure aphasic-like symptoms [5] and seizure, diffusion-weighted imaging (DWI) MRI was performed as soon as possible after brain CT and 90 minutes after her symptoms had developed. A diffusion-restricted lesion corresponding to her aphasia was found in the left middle and posterior temporal lobe, suggesting hyperacute ischemic stroke (Fig. 1B, C). However, on additional GRE images, there were multiple dot-like low signal intensities located in the same areas (Fig. 1D). We suspected that the findings were more likely reflective of vascular malformation combined with an ischemic lesion. We decided not to start IV r-tPA and considered further evaluation. The next day, she underwent digital subtraction angiography and the presence of DAVFs in the vein of Labbe was confirmed (Fig. 2A). Routine MRI showed gyral swelling and combined venous congestion (Fig. 2B, C). Electroencephalography was performed to exclude aphasic seizure, and no abnormal findings were observed. After admission, she received nadroparin 2,850 IU through subcutaneous injection and cilostazol 100 mg. The patient’s symptoms improved after treatment. Her NIHSS score on the 3rd day was measured at two points. The patient was discharged 7 days later with only mild aphasia.

DAVFs can develop anywhere within the intracranial dura mater. The clinical symptoms of DAVFs are diverse, ranging from mild (such as headache and tinnitus) to more severe (such as aphasia, hemiparesis, and coma) symptoms depending upon its location and the venous drainage pattern of arteriovenous shunting [6,7]. Like our case, DAVFs could be confused with acute stroke in the case of patients who arrived during the time window available for IV thrombolysis and presented with stroke-like symptoms. In addition, DAVFs are not seen on non-contrast CT and/or DWI, which are performed to diagnose stroke and reduce the time until IV injection of r-tPA. Although a diagnosis of DAVF is always challenging, susceptibility- or perfusion-weighted MRI has been recently reported to corroborate diagnostic clues of DVAFs [8,9].

The time window for applying IV thrombolysis in ischemic stroke is limited and fixed to 4.5 hours after symptom onset. Therefore, the decision regarding the use of thrombolytic agents must be made as quickly as possible. Even though the actual risk of using thrombolytic agents in the setting of a DAVF is not still known, an increased risk of intracranial hemorrhage is expected. Brain vascular malformations, including arteriovenous malformation, intracranial aneurysms, and DAVFs, require careful attention and an individualized approach with regards to intravenous thrombolysis [10]. In addition, this case illustrates that GRE MRI is helpful in finding hidden DAVF and plays an important role in the decision making regarding the use of IV thrombolysis.