Design of a multicentre study on neurosonology in acute ischaemic stroke

This report summarises the design and organisation of a multicentre study on neurosonology in acute ischaemic stroke. The Neurosonology in Acute Ischaemic Stroke Study will determine whether extracranial and transcranial Doppler and duplex sonography performed within 6 h after onset of stroke improves prediction of functional outcome if applied in addition to routine diagnostic admission investigations, i.e. medical history, standardised neurological examination, brain imaging by computed or magnetic resonance tomography, electrocardiography, and baseline laboratory examination. The primary hypothesis is that there is a consistent and persuasive difference between patients with an occluded middle cerebral artery and those with an open artery in terms of the functional deficit after 3 months. Power calculations are based on the assumption of α=0.05 (two-sided test) and a probability of a maximally mild functional deficit of 0.4. Detection of a 20% difference with a power of 0.8 resulted in a calculated sample of 400 patients to be observed. Calculation took into consideration that only 50% of admitted patients would have a moderate to severe neurological deficit of whom only 30% will have an occlusion of the corresponding middle cerebral artery. Furthermore, the study is designed to evaluate a difference of the functional outcome in relation to occurrence and time of recanalisation in-patients presenting with an initially occluded middle cerebral artery.