The state of the art for imaging acute cerebral ischemia dramatically changed after the efficacy of tissue plasminogen activator (tPa) was demonstrated. Neuroimaging now occupies a central role in patient management. Prompt performance and interpretation of the initial CT is critical to successful intervention. For imaging in acute stroke two approaches may be useful, depending on availability. Head CT scan with careful assessment for subtle signs of stroke combined with bedside vascular imaging using TCD provides optimal information to decide on thrombolytic therapy and establish an early prognosis. Of note, the currently recommended tPA protocol does not require vascular assessment. An alternative approach is urgent MR imaging with diffusion and perfusion-weighted imaging and intracranial MRA. This approach may be more time consuming and require greater resources, but provides additional information, which may allow better definition of risk of thrombolytic therapy and perhaps may identify patients who could benefit from reperfusion even if they present outside of the currently accepted time window. Given recent data suggesting that even within the 3-hour time window for starting treatment, earlier treatment is associated with better outcome, routine use of MR imaging cannot be advocated before the use of intravenous tPA for otherwise eligible patients. For diagnostic evaluation of stroke in the nonacute setting, defining both mechanism of stroke and risk factors can proceed in several phases, progressing to the next phase if the diagnosis remains uncertain (Fig. 8). Phase I evaluation should include brain imaging, screening of the major vessels supplying the region of ischemia, assessment for a cardiac source of embolism, and obtaining and blood tests to define associated medical conditions and risk factors. Finding occlusive vascular disease may not obviate the need for cardiac investigation, because many patients have coexistent disease in the heart, aorta, and cerebral vessels. Phase II studies may be indicated in patients with suspected intracranial stenosis or vasculitis or in young patients in whom no defined cause of stroke is found after phase I testing. At each step, results from previous tests should either confirm the hypothesis or lead to the generation of a new hypothesis concerning the cause of stroke or TIA, but the extent of testing may be modified depending on the patient's medical condition and available treatment options.
ASJC Scopus subject areas
- Clinical Neurology