The Exact Science of Stroke Thrombolysis and the Quiet Art of Patient Selection

Joyce S. Balami; Gina Hadley; Brad A. Sutherland; Hasneen Karbalai; Alastair M. Buchan


Brain. 2013;136(12):3528-3553. 

In This Article


The goal of neuroimaging is to help establish the clinical diagnosis as early as possible, as time is of the essence in management of acute stroke. The choice of brain imaging modality lies between CT and MRI (Jauch et al., 2013).

A non-contrast CT can easily distinguish ischaemic from haemorrhagic stroke and may also demonstrate early ischaemic changes or sign of arterial occlusion. The AHA/ASA recommends that either non-contrast CT or MRI be completed within 25 min of arrival at hospital, with interpretation by a skilled physician within a further 20 min (Latchaw et al., 2009; Jauch et al., 2013).

Multimodal Stroke Imaging

Multimodal CT and MRI techniques can provide a fast, reliable and comprehensive assessment of the presence and extent of ischaemic injury, perfusion status, vessel occlusion and collateral flow, and exclude intracranial haemorrhage and other mimics of acute ischaemic stroke, such as neoplasm and infection, through the combination of parenchymal, penumbral, and vascular imaging in a single study (Albers et al., 2006; Hopyan et al., 2010), potentially differentiating the reversible ischaemic penumbra from the irreversible infarct core, and enabling improved selection of patients who will benefit from reperfusion therapies (Schellinger et al., 2003; Albers et al., 2006). Multimodal imaging is also a valuable tool in patients with unknown time of symptom onset or 'wake-up' stroke. Whereas the multimodal CT protocol can be performed in <10 min, multimodal MRI may take 15–30 min (Leiva-Salinas et al., 2011); AHA/ASA guideline time constraints should be kept in mind. It is imperative that stroke physicians are familiar with the advantages and limitations of multimodal CT and MRI imaging techniques (Table 1).

Neuroimaging Scales

Several acute ischaemic stroke neuroimaging scores have been developed to improve detection and guide physicians in making better therapeutic decisions and prognostic predictions. Examples include the one-third middle cerebral artery territory method (hypoattenuation in less than one-third of the middle cerebral artery territory) (von Kummer et al., 1996; Silver et al., 2001), the Boston Acute Stroke Imaging Scale (BASIS) (Torres-Mozqueda et al., 2008) and ASPECTS (Barber et al., 2000) (Fig 1). ASPECTS is a standardized and validated 10-point scoring scale developed to quantify the extent of early ischaemic changes in the middle cerebral artery territory on non-contrast CT (Barber et al., 2000). Similarly, the posterior circulation ASPECTS is a predictive scale for quantifying posterior circulation changes (Puetz et al., 2008b). ASPECTS, in combination with specific clinical markers, has been found to be predictive of response to both intravenous (Coutts et al., 2004a) and intra-arterial therapies (Gupta et al., 2012). ASPECTS has been extended for use with magnetic resonance diffusion-weighted imaging (Kosior et al., 2010), quick symptomatic intracranial haemorrhage risk assessment before thrombolytic therapy (Singer et al., 2009), and for scoring of cerebral blood volume (Aviv et al., 2007). It has also been incorporated into clinical trials such as the Interventional Management of Stroke 3 (IMS III) trial (Broderick et al., 2013) and the Solitaire FR Thrombectomy for Acute Revascularisation (STAR) trial (NCT01327989) (

Figure 1.

Assessing the viability of tissue: the importance of imaging in informed patient selection for thrombolysis. (A and B) ASPECTS = 10 (no changes dictated). (C and D) ASPECTS = 3 (severe tissue damage). Patients with a good scan (A and B) have the potential to respond well to thrombolysis despite a clinically severe stroke. An ASPECTS of >7 predicts a favourable outcome. Patients with a poor scan (ASPECTS <7) (C and D) are less likely to benefit from thrombolysis. C = caudate; L = lentiform; IC = internal capsule; I = insular; M1,M2, M3, M4, M5, M6 = cortical regions.