Teaching Neuro Images : Artery of Percheron aneurysm masquerading as ICH spot sign.

A 50-year-old Japanese woman presented with left thalamic intracerebral hemorrhage (ICH). CT angiography demonstrated an ICH spot sign and intracranial vasculopathy consistent with Moyamoya disease (figure 1). Conventional angiography demonstrated that the spot sign was actually a pseudoaneurysm arising from the artery of Percheron (figure 2). Intracranial aneurysms may complicate Moyamoya disease and occur at the circle of Willis, distal peripheral arteries, or Moyamoya vessels at a ratio of 3:1:1.1 Aneurysms in thalamo-perforating arteries are rare2 and an artery of Percheron aneurysm in Moyamoya disease has not been reported. In Moyamoya disease, presence of a spot sign should prompt consideration for angiography.