I frequently get asked about white matter disease of the brain. It is commonly reported when MRI scans are carried out causing concern to patients and family alike. So in this blog post that is the topic we shall discuss.
Just what is white matter disease of the brain? As you all may be aware of in very simple terms the brain is made of grey matter (comprising the cell bodies of the neurons) and white matter (fiber tracts). Think of white matter disease as changes seen in the white matter of different parts (lobes) of the brain visualized on a MRI scan of the brain. Either the white matter appears scarred or atrophic. If the white matter is examined under the microscope, degenerative (ischemic) changes are visualized in the small blood vessels hence the term ischemic microvascular small vessel disease is sometimes used. A point to remember here is that these white matter changes visualized on the brain MRI can be seen in many different diseases of the brain-diseases as diverse as leukodystrophies, nutritional deficiencies, toxic drug exposures, vascular dementia and multiple sclerosis (MS). So the radiologist’s report invariably lists all these differential diagnoses and when patients read their MRI report they get worried. Many write in to me asking me if they have MS.
White matter changes on brain MRI need to be correlated with the patient’s history and examination findings and that is where I as a neurologist step into the picture. Let me explain with a few examples:
1. A 29-year-old woman with history of acute loss of vision in one eye (optic neuritis) . MRI brain shows white matter lesions in a characteristic distribution (perpendicular to the long axis of the lateral ventricles). In this case multiple sclerosis is high up in the differential.
2. A 29-year-old woman with history of episodic headaches which are usually unilateral, throbbing in quality and accompanied by nausea and photophobia (brights lights bother her during the headache episode). MRI brain shows a few non-specific white matter lesions scattered in the brain. In this case the most likely diagnosis is migraine headaches.
3. A 75-year-old woman with complaints of memory impairment. MRI brain shows white matter lesions scattered diffusely in the frontal and temporal lobes. In this case vascular dementia is the diagnosis which comes to mind.
Should white matter disease of the brain be treated: if the white matter disease of the brain represents ischemic white matter disease it may be prudent to address vascular risk factors such as better control of hypertension and diabetes, lowering the cholesterol and advising the patient to stop smoking. There is now increasing evidence that white matter disease may cause cognitive impairment and may coexist with other causes of memory impairment such as Alzheimer’s disease in the same patient. On the other hand if the white matter lesions are demyelinating lesions of MS, then treatment is aggressive treatment of MS. If they are due to migraine then usually no treatment is warranted.
In children the cause of white matter disease of the brain is different. Various leukoencephalopathies, metabolic, hereditary and degenerative diseases are in the differential and have to be screened for and ruled out systematically.
I hope this small post helps to answer some of my readers concerns.
Nitin K Sethi, MD