Venous loop mimicking middle cerebral artery bifurcation aneurysm on computed tomographic angiography--case report

CT angiography has been widely used for the detection of cerebral aneurysm. However, there are still limitations despite improving CT angiographic techniques. We describe the unusual case of the detection of a false-positive aneurysm on CT angiography.

A 64-year-old man presented with a 14-day history of severe headache and nuchal rigidity. Brain CT demonstrated no subarachnoid hemorrhage, but cerebrospinal fluid appeared xanthochromic in 3 successive tubes after lumbar puncture. Subsequent CT angiography suggested an aneurysm at the bifurcation of the left MCA. However, at operation, prominent sylvian vein superimposed on the bifurcation of the left MCA, and there was no aneurysm. Follow-up monitoring with conventional angiography at 2 weeks showed no abnormal findings. The patient recovered uneventfully.

The case demonstrates that although CT angiography has a reportedly high specificity and sensitivity for the detection of intracranial aneurysm, careful interpretation is required to diagnose intracranial aneurysms.