Assessing success after cerebral revascularization for ischemia

Cerebral revascularization continues to evolve as an option in the setting of ischemia. The potential to favorably influence stroke risk and the natural history of cerebrovascular occlusive disease is being evaluated by the ongoing Carotid Occlusion Surgery Study and the Japanese Extracranial-Intracranial Bypass Trial. For those patients who undergo bypass in the setting of ischemia, four key areas of follow-up include functional neurological status, neurocognitive status, bypass patency, and status of cerebral blood flow and perfusion. Several stroke scales that can be used to assess functional status include the National Institutes of Health Stroke Scale, Bathel Index, Modified Rankin Scale, and Stroke Specific Quality of Life. Neurocognition can be checked using the Repeatable Battery for the Assessment of Neuropsychological Status, among other tests. Bypass patency is checked intraoperatively using various flow probes and postoperatively using magnetic resonance angiography (MRA) or computed tomographic angiography (CTA). Cerebral blood flow and perfusion can be assessed using a host of modalities that include positron emission tomography (PET), xenon CT, single photon emission computed tomography (SPECT), transcranial Doppler (TCD), CT, and MR. Paired blood flow studies after a cerebral vasodilatory stimulus using one of these modalities can determine the state of autoregulatory vasodilation (Stage 1 hemodynamic compromise). However, only PET with oxygen extraction fraction measurements can reliably assess for Stage 2 compromise (misery perfusion). This article discusses the various clinical, neuropsychological, and radiographic techniques available to assess a patient's clinical state and cerebral blood flow before and after cerebral revascularization.