Intracranial dissecting aneurysm causing subarachnoid hemorrhage: the role of computerized tomographic angiography and magnetic resonance angiography.

Background: With increasing frequency, dissecting aneurysms of the intracranial arteries are recognized as a possible cause of subarachnoid hemorrhage (SAH). In the presence of a dissecting aneurysm, angiographic changes may be subtle at presentation and correct diagnosis often requires serial angiograms. We report a patient with a dissecting aneurysm of the anterior cerebral artery (ACA) causing SAH, in whom less invasive diagnostic tools, such as high-resolution computerized tomographic angiography (CTA) and magnetic resonance angiography (MRA), were helpful in confirming the diagnosis and in following the evolution of the dissection.

Case Presentation: We present this 51-year old woman who experienced the sudden onset of severe headache without associated neurological deficits. Head CT showed SAH with blood in the interhemispheric fissure, suggesting a ruptured ACA aneurysm. Serial cerebral angiograms failed to demonstrate an aneurysmal sac, but showed evolving irregularities of the ACA consistent with a dissecting aneurysm. These findings were confirmed by CTA and MRA. The patient was treated conservatively and made an excellent recovery. A MRA obtained 2 months later showed slight improvement of the previously visualized ACA dilatation.

Conclusion: Serial angiograms are often required to confirm the diagnosis and to follow the evolution of an intracranial dissection. With recent advances in neuroradiological techniques, however, critical information can be obtained by less invasive imaging studies, such as CTA and MRA.