MRI best bet for brain structure, blood vessels

DEAR DR. ROACH: In 2016, I had a brain MRI without contrast, which showed chronic small vessel brain disease and a remote lacunar infarct in the right cerebellum.

This brain MRI was done because I was experiencing insomnia, along with dizzy spells, brain fog, poor judgment and difficulty walking and driving.

In May 2017, I had a brain CT scan because my blood pressure was high and I was having some pain on the left side of my head. (For years, I had experienced migraines or cluster headaches on the right side, but they ceased about eight years ago.) The brain CT scan was read as “normal.”

Why would the CT scan not show the damage that the MRI showed a year ago? I was told that the damage was permanent. I still can tell a difference in my thinking and memory skills, which were the result of the stroke that the MRI showed.

ANSWER: An MRI is a much more sensitive test than a CT scan for looking at the brain structure and its blood vessels. The back part of the brain, called the posterior fossa, contains the cerebellum, and that area in particular is very difficult for the CT to show.

A CT scan is quick and useful for making sure there is no bleeding inside the head. But an MRI simply has much better resolution of the soft tissues, necessary to see small-vessel disease.

“Lacuna” is Latin for “pool” (the word “lagoon” comes from the same root), so a lacunar infarct is a small stroke that looks like a pit or pool.

High blood pressure is a common underlying cause. Keeping the blood pressure down is the single most important factor in preventing another stroke.

Dr. Roach regrets that he is unable to answer individual letters, but will incorporate them in the column whenever possible. Readers may email questions to ToYourGoodHealth@med.cornell.edu or request an order form of available health newsletters at 628 Virginia Dr., Orlando, FL 32803.