(p. 1063) Imaging the central nervous system in the critically ill 

Imaging techniques play a major role in managing patients with acute severe neurological signs. Initial evaluation of patients with traumatic brain injuries is best performed with a computed tomography (CT) scan, both for its ability to demonstrate most of the significant lesions and for logistical reasons. Magnetic resonance imaging (MRI) is able to provide more subtle information, as well as prognosis indicators, but is impractical until the patient’s condition has been stabilized. MRI has the same advantages for assessing anoxic brain injuries. In strokes, MRI has become the technique of choice, as it is able to highlight new lesions among older ones, and can identify ischaemic lesions only a few minutes after the event. At the same time MRI can identify or exclude contraindications for intravenous thrombolysis. Subarachnoid haemorrhages are best initially assessed with CT followed by a digital suppression angiogram to identify arterial aneurysms or arteriovenous malformations. In spine imaging, CT scan works the best in indicating traumatic bone lesions, while MRI is unsurpassed in examining the spinal cord and ligamentous injuries, and can provide prognostic indicators of the expected functional outcome.