Neuroimaging correlates of cognitive and functional outcome after traumatic brain injury.

Magnetic resonance imaging (MRI) may provide an estimate of the severity of diffuse axonal injury by quantitative measurements of atrophy of white matter tracts (such as corpus callosum) and of ventricular enlargement (particularly the third ventricle). However, most MRI studies failed to reveal consistent relationships between the pattern of neuropsychological impairments and the site and extent of focal structural lesions after traumatic brain injury. Functional neuroimaging techniques, such as positron emission tomography or functional MRI, may reveal areas of cerebral dysfunction in regions that look structurally intact on MRI. Studies using these techniques have suggested that the cognitive and behavioural disturbances of traumatic brain injury could be related to a defective activation of a prefrontal-cingulate network.