Prognosis of intracranial dissection relates to site and presenting features.

Intracranial arterial dissection is relatively rare and generally considered to have a worse outcome than extracranial arterial dissection. It is a clinically significant entity that can cause severely disabling ischaemic stroke or subarachnoid haemorrhage (SAH). Only a few large case series of intracranial arterial dissection have been reported, particularly in the anterior circulation, but it is being increasingly recognized with advances in non-invasive angiographic diagnostic procedures. Patients with posterior circulation dissection appear to present more commonly with SAH and are traditionally said to have a worse outcome. Treatment options remain controversial and include medical therapy, as well as endovascular and surgical intervention. We reviewed the clinical features and outcome of 25 patients who had been treated for intracranial dissection at The Royal Melbourne Hospital over a period of 5 years. We recorded patient age, clinical presenting features, neuroimaging findings, treatment, and outcome assessment at 90 days using the modified Rankin Score (mRS). Eleven patients had anterior circulation dissection, while 14 had posterior circulation dissection; and overall 12 patients had cerebral ischaemia while 13 had subarachnoid haemorrhage (SAH). Almost all intracranial arterial dissections occurred spontaneously, without a history of trauma. Patients were relatively young, especially those in the group with ischaemia, with an average age of 39 years. Hypertension was the most commonly identified vascular risk factor. Eight out of 12 patients with ischaemia (66.7%) had anterior circulation dissection, while posterior circulation dissection occurred in 10 of 13 patients with SAH (76.9%). Location of anterior circulation dissection was variable, while the terminal vertebral artery segment was most commonly involved in the posterior circulation group. Most of the patients in the ischaemic group received medical therapy (n=10/12), while 10 out of 13 (76.9%) patients with SAH underwent endovascular and/or surgical intervention. There was a trend towards more favourable outcome at 90 days (mRS ≥ 3) in the ischaemic group (n=10/12, 83.3%) compared to the SAH group (n=6/13, 46.2%), but this did not reach statistical significance (p value=0.097). The mortality rate was 16.7% (n=2/12) in the ischaemia group, and 7.7% in the SAH group (n=1/13), not significant. Among all the ischaemic group patients who received medical therapy, there were no deaths or development of secondary intracranial bleeding complications including SAH at 90 days. Our series suggest that it is possible to divide patients with intracranial dissection into two groups: (i) an ischaemia group, associated with a more favourable clinical outcome even when treated with antiplatelet or anticoagulation therapy; or (ii) a SAH group with a less favourable prognosis. The mortality rate, especially in patients with SAH who are generally treated with endovascular and/or surgical intervention, is less than previously reported. Anterior circulation involvement appears more common than traditionally perceived. The spontaneous occurrence of intracranial dissection in a relatively young age group, the predominant site of dissection in the artery at some distance from its tethered proximal segment, and the commonly observed hypertension, together raise the possibility of spontaneous dissection in arteries prematurely weakened by accelerated atherosclerosis.