[A dissecting aneurysm of the posterior inferior cerebellar artery was reduced spontaneously during conservative therapy: case report].

We report here a case of a patient with a dissecting aneurysm of the anterior medullary segment of the posterior inferior cerebellar artery (PICA) which presented with Wallenberg's syndrome. A 32-year-male presented with an unusual case of Wallenberg's syndrome due to a dissecting aneurysm of the PICA manifesting as a sensation of heaviness in the occipital region and vertigo. The occipital symptoms persisted and vertigo and vomiting developed after 6 days. Numbness developed on the left side of the patient's face, and hyperalgesia on the right side of the body. The diagnosis of Wallenberg's syndrome was based on the above findings. MRI revealed infarction of the lateral aspect of the medulla oblongata and MR angiography revealed dilatation in the proximal portion of the left PICA. Digital subtraction angiography revealed that the left vertebral artery was essentially normal, but there was a spindle-shaped dilatation in the proximal portion of the left PICA. We carried out conservative therapy at the patient's request and 3D-CTA revealed that the dissecting aneurysm was markedly reduced in size seven months after the onset. Dissecting aneurysms of the intracranial posterior circulation have been shown to be less uncommon than previously thought. However, those involving the PICA without involvement of the vertebral artery at all are extremely rare. The natural history of the dissecting PICA aneurysm was unknown, and the indication for surgical treatment of such aneurysms remains controversial. Management options are conservative treatment, open surgical treatment including wrapping, trapping, and resection with reconstruction, but almost all of the patients underwent radical treatment to prevent rupture of the aneurysm. However we had no knowledge of the risk of rupture of a PICA dissecting aneurysm presenting with ischemic symptoms. We have reviewed the well-documented 15 cases of dissecting aneurysms of the PICA reported in the literature and we discuss the management of the dissecting PICA aneurysm presenting with ischemic symptoms.