[A case of subacute subarachnoid hemorrhage without xanthochromic cerebrospinal fluid--usefulness of emergent MRI].

We reported a case of subacute subarachnoid hemorrhage with watery clear cerebrospinal fluid. Emergent magnetic resonance image was useful not only for diagnosis by fluid attenuated inversion recovery image but also for evaluation of cerebral ischemia and vasospasm by magnetic resonance angiography, diffusion weighted image and perfusion weighted image. A 50-year-old man presented disturbance of consciousness and dysarthria. Neither computed tomographic scan nor cerebrospinal fluid study could diagnose subarachnoid hemorrhage clearly. However, emergent fluid attenuated inversion recovery image showed the show subarachnoid hemorrhage as high signal intensity. Diffusion weighted image showed multiple, round hypersignals both in the white and gray matter. In the area with diffusion hypersignal, the apparent diffusion coefficient value was 0.57 x 10(3) mm2/sec. Perfusion weighted image showed normal cerebral blood volume but prolonged mean transit time in the territory of the right middle cerebral artery. Magnetic resonance angiography revealed an aneurysm at the anterior communicating artery and severe vasospasm on the bilateral anterior cerebral artery, the right middle cerebral artery. Thus we are able to diagnose subarachnoid hemorrhage due to a ruptured anterior communicating artery aneurysm. The hyperintensity of the diffusion weighted image and the fluid attenuated inversion recovery image was caused by cerebral ischemia from vasospasm. After conservative therapy during the period of vasospasm, successful surgical clipping was performed with full clinical recovery.