White matter brain disease results in the degeneration of white matter, which creates a large portion of the brain. The primary form of white matter brain disease is multiple sclerosis, which results in the destruction of the myelin sheath. In multiple sclerosis, there is defective formation or maintenance of the myelin because of dysfunction of the oligodendrocytes, a type of glial cell. Other types of white matter brain diseases include progressive multifocal leukoencephalopathy, post-infectious encephalitis and HIV encephalitis. White matter brain diseases have a variety of different symptoms that can impair visual, motor, sensory and cognitive functions.
White matter is located in the central and subcortical regions of the cerebral and cerebellar hemisphere of the brain. White matter makes up 60 per cent of the total brain volume, and can be identified in a scan from its white colour, compared to grey matter. There is not as large a supply of blood in the white matter as there is in grey matter, and thus is more susceptible to ischemia. White matter contains the major commissural tracts, cortical association fibres, and all cortical afferent and efferent fibres.
A variety of different visual problems can arise from white matter brain diseases. Examples include blurred vision, double vision and abnormal pupil responses. In addition, patients may also have problems controlling their eye movements, such as lack of coordination or jerky movement of the eyes.
White matter brain disease patients may also have difficulty with motor responses and movement. Types of motor problems include muscle weakness and wasting, paralysis---either mild, partial or total, stiffness, twitching and other involuntary jerking motions, involuntary leg movements, loss of coordination, restricted movement of the limbs, slow movement of the limbs, dragging of the limbs and problems with posture.
Sensory problems can also occur when there is damage to the white matter. These include numbness, strange sensations such as tingling or vibrations, loss of sensation, experiencing pain without a cause and losing the awareness of limb location.
Finally, white matter brain disease can interfere with cognitive functions. Examples of cognitive problems as a result of white matter brain disease are short-term and long-term memory problems, slow word recall, speech impairment, depression, mood swings, anxiety and other mood disorders. Other cognitive problems include sleep disorders, fatigue and impairments to speech comprehensive and production.