White matter lesions, migraine and memory problems: a question and an answer

One of the readers of my blog wrote in with a question about white matter lesions on brain MRI. Her question and my response to it follows.

Question:

I was recently referred to a neurologist by my primary care physician for treatment of my migraines. While migraines have a been a part of my life, they have been occuring with greater frequency of late (10+ per month). To rule out any other cause of my migraines, the doctor ordered an MRI. The MRI revealed 20+ white matter lesions throughout my brain (various locations, various sizes). The neuro was at a loss as to why I had so many. I did inform him that approx 15 years ago I had unilateral ect, and asked if perhaps this had caused it? I also let him know that I was experiencing significant memory issues (forgetting short term and long term memories, and even blanking on spelling my own last name for a minute or two). I asked him if ect could be responsible? The neuro has since followed up with me and has stated that ect could NOT be responsible for the lesions, and was not likely to be responsible for my recent, memory issues. I have been tested for MS, lyme, infection, etc. – all negative. I do not suffer from depression or take any other medications which would cause memory issues. Any thoughts? What else could cause these lesions? Is these any research at all into lesions and ect? I am trying to get into Neuropsych testing to determine the extent of my memory loss. The migraines are now currently being sufficiently controlled with Imitrex.

Answer

Thank you for writing in to me M.  White matter lesions are commonly documented on brain MRI done for various reasons (in your case as a work up of migraines). The differential diagnosis of white matter lesions is broad and varies based on the age of the patient. In “most” adult patients especially those with risk factors for microvascular disease such as diabetes mellitus, essential hypertension (high blood pressure), dyslipidemia (high cholesterol), current or past heavy smokers these white matter lesions respresent small vessel disease (also referred to as microvascular ischemic small vessel disease). Meaning that the small blood vessels in the brain are showing signs of ischemia (lack of blood flow). So when I see extensive microvascular (small vessel) disease on a patient’s MRI scan of the brain what I worry about is the possibility of a stroke in the future. As a neurologist, I then try to identify his stroke risk factors and attempt to modify them. If he has high blood pressure and is not an on anti-hypertensive medication–start an appropriate anti-hypertensive, if he is already taking a blood pressure medication but the blood pressure is still not well controlled then I may need to increase the dose of his medication and/or change it. As per the new Joint National Commission guidelines broadly speaking the lower the blood pressure the better it is (earlier a blood pressure of 140/80 mm Hg was accepted as ” normal”, now we aim for level of 120/70 mm Hg). If the patient’s blood sugar is high (fasting blood sugar greater than 107mg/dl), I would investigate him for diabetes mellitus. For this blood sugar is tested in a fasting state and after meal (post prandial). There are normal values and if the patient’s blood sugar exceeds these normal values, then he has diabetes mellitus. Diabetes mellitus can be controlled by a combination of dietary modification, exercise, oral hypoglycemic medications (pills) and/or insulin injections. If the lipid profile is deranged (high total cholesterol, high low density lipoprotein, high triglycerides and low high density lipoprotein), then again dietary modifications, exercise and lipid lowering medications (statin group of medications such as Lipitor are one example) are recommended.

Now what do white matter lesions represent when they are seen in a young person (like for example in a  young lady 25 years of age)?  The main differential and what concerns most patients and physicians alike is whether this could represent multiple sclerosis. I have written about this before and again want to emphasize that the diagnosis of multiple sclerosis is a clinical one and not based solely on the MRI scan of the brain. The MRI scan always has to be interpreted after taking the history and examination findings into consideration. Also the white matter lesions of ischemic small vessel disease are different from the white matter lesions (plaques) of multiple sclerosis. In multiple sclerosis the lesions have a characteristic appearance and distribution in the brain.

White matter lesions can also be seen in many other infectious (Lyme disease is a good example) and inflammatory conditions (sarcoidosis, connective tissue diseases which cause vasculitis in the brain). Most of these diseases can be identified with the help of a good history and some basic tests.

White matter lesions are also commonly seen in people who suffer from migraines (more commonly seen in women migraine sufferers). Why do white matter lesions occur in migraine patients. While there are many theories of migraine pathophysiology, migraine is a vascular headache and hence the blood vessels are again involved.

Do white matter lesions cause memory problems. Now that is a tough question to answer. When I see extensive white matter disease in a brain MRI, it tells me about the health of the brain and the blood vessels. If a person has extensive white matter disease, the same pathology shall be seen in the blood vessels of the heart. So they are prone to both heart disease and brain disease (stroke, transient ischemic attacks). While Alzhemier’s disease is the most common primary dementia, vascular dementia is exceedingly common too. What is vascular dementia? As the name suggests, it is dementia (memory impairment, problems in multiple cognitive domains) caused due to multiple small strokes in the brain or rather strokes in a strategic location. These strokes occur over a period of time and may be clinically silent (meaning that the patient may not even realise that he has suffered a stroke). The small strokes over a period of time though add up and cause vascular dementia.

I hope this helps in answering some of your questions M. My advise to you is to follow up with your primary care physician and the neurologist. They shall help guide your work-up further.

Personal Regards,

Nitin Sethi, MD