Magnetic resonance imaging of the brain and spine.

The efficacy of magnetic resonance imaging (MRI) in the diagnosis of diseases of the central nervous system is reviewed. MRI, computed tomography (CT) and certain radionuclide studies are compared in the evaluation of intracranial tumours, cerebral vascular disease, multiple sclerosis and other white matter diseases, dementia, head injury, infection, epilepsy, spinal lesions and in paediatric central nervous system disorders. The measurement of cerebrospinal fluid volumes and dynamics by MRI is discussed. MRI most clearly has advantages where CT is degraded by bone hardening and streak artefacts (spine, skull base, posterior and temporal fossa, sella and parasellar regions) and in diseases in which the X-ray attenuation of the suspected lesion differs little from normal parenchyma (paediatric brain disorders, demyelination and dysmyelination, early oedema associated with infarction, infection or low-grade infiltrating neoplasm, subacute and chronic haemorrhage and lesions in the spinal subarachnoid space and cord). Elsewhere MRI and CT should be seen as complementary rather than competitive methods of imaging. In spite of an absence of information about the contribution of MRI to management decisions and a lack of rigorous, prospective controlled trials, MRI will play an increasing role in the diagnosis of diseases of the central nervous system.