Dissecting aneurysm of the posterior communicating artery.

A 36-year-old male presented with an extremely rare dissecting aneurysm of the posterior communicating artery manifesting as severe occipital headache. Magnetic resonance (MR) imaging revealed a partially thrombosed aneurysm of the right posterior communicating artery and angiography showed the pearl and string sign. Three months later, repeat angiography showed that the aneurysm was completely thrombosed and the posterior communicating artery was occluded. Magnetic resonance (MR) imaging showed an intimal flap. These neuroradiological findings demonstrated that the aneurysm was a dissecting aneurysm of the right posterior communicating artery. He was discharged with no neurological deficit.