Brain Imaging

Brain Imaging

Several methods of brain imaging are available to assist in di-agnostic assessment. Table 19.17 lists some indications for brain imaging.

Computed tomographic (CT) scans and magnetic resonance imaging (MRI) can be used to assess brain structure and are useful in detecting such abnormalities as mass lesions (central nervous sys-tem neoplasms, certain infections and hemorrhage), calcifications, atrophy, or areas of infarction. Mass lesions should be suspected in situations in which focal or lateralizing abnormalities such as focal weakness, unilateral disturbances in reflexes and increased pupil-lary size are found during the neurological examination. Other situ-ations that call for brain imaging include the work-up of a patient with dementia to look for brain atrophy or lacunar infarctions; the evaluation of new-onset psychosis, acute onset of aphasia or mem-ory loss and neglect syndromes; the evaluation of normal-pressure hydrocephalus (a syndrome characterized by a wide-based gait, de-mentia and urinary incontinence); and demyelinating conditions.

Whereas CT and MRI provide visualization of brain struc-ture, positron emission tomography (PET), single photon emis-sion computed tomography (SPECT) and regional cerebral blood flow allow investigators to study brain functioning by assessing which areas of the brain are stimulated during various types of mental activity.