Magnetic resonance imaging of the brain
White matter hyperintensities are common in MRIs of asymptomatic individuals, and their prevalence increases with age from approximately 10%-20% in those approximately 60 years old to close to 100% in those older than 90 years.
White matter hyperintensities are more common in patients with a history of cognitive impairments, dementia, or cerebral vascular disease.
Aging and hypertension are the main predictors of white matter hyperintensities.
Other risk factors associated with white matter hyperintensities include diabetes, hyper cholesterolemia, smoking, carotid artery disease, atrial fibrillation , and heart failure.
Twin studies suggest that white matter hyperintensities have. a heritability factor of 55-80%.
White matter hyperintensities are a predictor of future risk of stroke, declining global cognitive performance, executive function, and processing speed, dementia-Alzheimer types, vascular and mixed , and death particularly due to cardiovascular causes.
The presence of white matter hyperintensities on MRI are associated with functional decline, gait disturbance, and depression because they disrupt neural networks.
Magnetic resonance imaging (MRI) of the nervous system uses magnetic fields and radio waves to produce high quality two- or three-dimensional images of nervous system structures.
It does not use of ionizing radiation or radioactive tracers.
Advantages of MRI of the brain over computed tomography of the head is better tissue contrast, fewer artifacts than CT when viewing the brainstem, superiority for pituitary imaging.
MRI of the brain may be less effective at identifying early cerebritis than CT.
In the case of a concussion, an MRI should be avoided unless there are progressive neurological symptoms, focal neurological findings or concern of skull fracture on exam.
In analysis of the fetal brain, MRI provides more information about gyration than ultrasound.
T1-weighted (T1W) images: Cerebrospinal fluid is dark.
T1-weighted images are useful for visualizing normal anatomy.
T2-weighted (T2W) images: CSF is light, but fat and is white matter that is darker than with T1.
T2-weighted images are useful for visualizing pathology.
Diffusion-weighted images (DWI): DWI uses the diffusion of water molecules to generate contrast in MR images.
Proton density (PD) images: CSF has a relatively high level of protons, making CSF appear bright.
Gray matter is brighter than white matter with proton density (PD) images
Fluid attenuation inversion recovery (FLAIR): useful for evaluation of white matter plaques near the ventricles.
Fluid attenuation is useful in identifying demyelination.