2 - Limitations of current brain imaging modalities in stroke

Summary

Introduction

The successful management of stroke patients requires the ability to confirm the diagnosis, identify the site, extent and age of the lesion, and determine underlying pathophysiology. Several studies have made it clear that this cannot be done on the basis of clinical findings alone. At the most basic level, clinicians are unable to accurately differentiate between cerebral infarction and primary intracerebral hemorrhage. Cerebral imaging is therefore a prerequisite in the management of almost all stroke patients.

Techniques such as computed tomography (CT), magnetic resonance imaging (MRI), positron emission tomography (PET) and single photon emission computed tomography (SPECT) have provided a window onto the structural and functional changes that occur during stroke can be examined and have revolutionized our understanding of the pathophysiology of ischemia. The advent of thrombolytic therapy has exposed a need for imaging techniques that enable the more rational selection of patients for potentially hazardous treatments. Each of these currently used brain imaging techniques has limitations in such a role and these will form the focus of this chapter.

Patient factors

There are a number of logistic and technical problems related to the performance of all imaging studies in stroke patients. These difficulties relate to a patient's emotional and physical state in the immediate hours after symptom onset. Fear, confusion, language disturbance, and physical deficits may all affect the ability to comprehend or follow commands. Patients are often restless, and frequently become more so with prolonged scanning protocols.