DEAR DR. ROACH: I am an 84-year-old male in excellent health. In 2009, I had a stroke, which the doctors called a ”sensory stroke.” I was told that I was very lucky to come out of it with no paralysis. What I do have is partial numbness on my left side, especially in my left arm, hand and side of my face. I don’t have any pain. The doctor prescribed gabapentin. I am taking 2,400 mg daily, which gives me some relief but is by no means a cure. Is there anything out there that might help me? — R.L.G.

ANSWER: A stroke is a loss of brain function that does not immediately recover. It is due to the death of cells in the brain, but what part of the brain it happens in and how much of the brain is affected are of primary importance in determining the severity of stroke. A stroke may impair strength, speech or cognitive functions.

A pure sensory stroke — one that does not cause weakness or loss of brain function — usually is due to damage to a small area of the thalamus, called a lacunar infarct (”lacuna” meaning ”lake,” and ”infarction” meaning ”cell death”). Recovery from strokes occurs most commonly in the six to 12 months after the stroke.

Gabapentin is frequently used for pain that is related to nerve damage, especially in people with pain as a result of shingles or due to diabetic neuropathy. Some people with thalamic strokes have terrible pain. However, gabapentin doesn’t always work for pain or numbness. When it does, it is rarely 100 percent effective. I wouldn’t recommend a higher dose than the one you are on; I often see people on doses that may be too low to be effective.

Other potentially effective medication options include pregabalin and amitriptyline; nonmedication options include sensory retraining therapy and massage.

DEAR DR. ROACH: I read that vitamin C may improve athletic performance. Is there any truth to that? What about preventing colds in athletes? — H.C.

ANSWER: I found good evidence that a diet high in fresh fruits and vegetables (five or more servings per day) led to improved athletic performance in several sports. However, high-dose vitamin C supplementation led to worsened athletic performance.

The data on marathoners and other endurance athletes is complex. Among elite-level athletes, there is some evidence that vitamin C reduced cold onset by nearly 50 percent. Interestingly, runners training for more than 60 miles per week have double the risk of developing colds, compared with those who run less than 20 miles per week.

DEAR DR. ROACH: In a recent column, you discussed body mass index and gave directions for how to calculate it, but it required metric measures. I have no idea how much I weigh in kilograms nor how tall I am in meters. However, I found directions for calculating BMI using feet, inches and pounds. Divide weight in pounds by the square of height in inches, and multiply the result by 703. — S.K.

ANSWER: I thank S.K. for this alternate way of calculating BMI. BMI is a useful but imperfect tool for measuring a healthy weight. A BMI below 19 is considered high risk for undernourishment, while a BMI over 30 is obese, and a BMI over 35 is considered morbidly obese.

I often discuss cholesterol levels in mg/dL: To convert these to mmol/L, divide by 38.67.

READERS: The booklet on herpes and genital warts explains these two common infections in detail. Readers can obtain a copy by writing: Dr. Roach Book No. 1202, 628 Virginia Dr., Orlando, FL 32803. Enclose a check or money order (no cash) for $4.75 U.S./$6 Can. with the recipient’s printed name and address. Please allow 4-6 weeks for delivery.

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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. Health newsletters may be ordered from www.rbmamall.com.