International Intracranial Dissection Study

Cervicocephalic artery dissection corresponds to a hematoma in the wall of a cervical or an intracranial artery and is an important cause of stroke in children and young and middle-aged adults. While extracranial cervical artery dissection (CeAD) has been extensively studied and described, less information is available on pure intracranial artery dissection (IAD) not involving the cervical portion of the artery. Early reports were based exclusively on autopsy series, hence biased towards the most severe cases. The incidence of IAD is unknown, but is probably lower than the incidence of symptomatic CeAD in populations of European origin. The proportion of IAD among all cervicocephalic dissections varies substantially between ethnic and age groups, and depending on study recruitment strategies and ascertainment methods. Indeed, recruitments through departments of neurology are biased towards CeAD and IAD presenting with local symptoms and/or ischaemic stroke while recruitments through departments of neurosurgery or interventional neuroradiology are biased towards IAD presenting with subarachnoid haemorrhage (SAH).Therefore, patients with IAD are managed not only by neurologists, but also by neurosurgeons, and interventional neuroradiologists, each having an incomplete picture of the disease.

The vast majority of reported series of IAD patients come from Asian countries and IAD affects the posterior circulation more frequently than the anterior circulation in these series. This contrasts with CeAD and saccular intracranial aneurysms, which most commonly affect the anterior circulation. Due to treatment and publication bias little is known about the natural history of IAD. Overall, IAD is assumed to have a more severe course than CeAD, with a more ominous outcome in patients with SAH IAD than in patients with non-SAH IAD. Furthermore, little information is available on the risk of recurrent IAD as well as risk for recurrent ischaemic and haemorrhagic events. Radiological diagnosis of IAD can be challenging given the small size of intracranial arteries, and the subtle and non-specific radiological signs which tend to evolve with time.

The optimal treatment of IAD is unknown. There are no randomised trials and only observational studies with relatively small sample sizes are available, thus providing a very low level of evidence. Patients with SAH IAD are usually treated by surgery or endovascular procedures because up to 40% of the patients experience re-bleeding within the first days after the event. Various surgical and endovascular treatment methods have been proposed for intracranial dissecting aneurysms. When patients are in poor clinical condition or treatment has an unacceptably high complication risk, it can be decided to withhold from surgical or endovascular treatment. In addition, Most non-SAH IAD patients have been treated medically, but the choice of antithrombotic therapy (anticoagulants or antiplatelet agents) has been evaluated neither in randomised trials nor in systematic reviews and meta-analyses of observational data. As a consequence, there is currently no consensus on optimal treatment of IAD.

• Recurrence of cervico- cerebral dissection [Time frame: 90 days, 180 days, 12 months]
• Recurrence of stroke [Time frame: 0-10 days, 90 days, 12 months after diagnosis]
• Change in Modified Rankin Scale score (mRS score) from before diagnosis to follow up [Time frame: 0-10 days, 90 days, 12 months after diagnosis]
• Change in occupational status from before diagnosis to follow up [Time frame: 0-10 days, 90 days, 180 days, 12 months after diagnosis]
• Mortality [Time frame: 0-10 days, 90 days, 180 days, 12 months after diagnosis]
• Increase or reduction in size (>50% local degree of stenosis) or disappearance of stenosis at 6 months (in patients with stenotic and occlusive dissection) [Time frame: 180 days after diagnosis]
• Increase or reduction in size (> 20% maximal diameter) of aneurysms at 6 months (in patients with aneurysm) [Time frame: 180 days after diagnosis]