Variety of Health Concerns Can Cause Numb Feet

Q: My right foot is quite numb and has been for two or three years. Now it has spread to my left foot. I am 86 years old; I can walk but my balance is poor. I had a tumor removed from my brain 60 years ago. Would that have anything to do with it? I have been healthy most of my life and I exercise, eat well and sleep well.

A: Our sense of touch is amazing. Innumerable nerve branches must travel from the skin to the spinal cord and then up to the brain where chemical and electrical information is translated into sensations such as pain, heat, cold or light touch. A single nerve cell must connect the skin to the spinal cord, so the nerve cells that sense touch in the feet have to be very long, and thus, are very susceptible to any sort of damage.

Brain surgery may cause numbness by damaging brain cells, but I expect you would have noticed any effect from surgery right after the surgery occurred. Or, if your brain tumor recurred, it could damage brain cells nearby, but this is unlikely.

Numbness can also be caused by anything that upsets the nerve cell's delicate chemistry. Examples include diabetes, vitamin deficiencies, liver or kidney disease, cancer, Lyme disease and many drugs. In this country, diabetes is the most common cause of foot numbness, but the numbness usually occurs after long-standing diabetes.

You need to ask your doctor to find out the source of your problem, but sometimes we are unable to find a specific cause for numbness.

Q: I'm a 68-year-old male. A few years ago I had bypass surgery. My surgeon gave me only a 10% chance to survive but I recuperated. When I was released from the hospital, the only thing to remind me of the surgery (besides the scars on my chest and legs) was a partial numbness in my right foot. An ultrasound showed blood clots and blockages in both legs. My doctor prescribed a blood thinner and the pain in my legs stopped, but the numbness continued. I was offered angioplasty treatment but I was worried about the risks. What should I do for my numbness?

A: In your case, the numbness is probably a result of surgery on your legs. For bypass surgery, the long straight veins in the legs are removed to use as new blood vessels for your heart. Sometimes the cut nerves do not completely heal. Another explanation of your numbness may be a small stroke during or after surgery; a stroke may result in permanent damage to the brain cells that sense touch in your leg.

Usually, blood clots in the veins of your legs do not cause numbness, although they may cause swelling, discomfort and skin changes. Also, blockages in the arteries of your legs usually do not cause numbness but can certainly lead to leg pain, just like blockages in the arteries to the heart can lead to chest pain.

If your leg pain has subsided, you may not need the angioplasty surgery to open up the artery blockages.

Julie L. Mitchell, MD, MS, is an Assistant Professor of Medicine at the Medical College of Wisconsin. She practices internal medicine at the Froedtert & Medical College General Internal Medicine Clinic – East. Her column also appears in the Milwaukee Journal-Sentinel.

"Dear Doctor" is a compilation of patient questions answered by doctors from the Medical College of Wisconsin.