THE CLINIC: Spinal Disc Fluid Loss and Leg Weakness

QUESTION:

I am 55 years old and have been a marathoner since the age of 18. I am 5’ 7”, 125 pounds, and my marathon times range from 2:26 (age 32) to 3:28 (Boston ‘04). I have had plenty of injuries—most notably, to my hamstrings—but none have been terribly serious. About two years ago I suddenly felt a decrease in power in my left leg. Sometimes mid-stride my left shoe hits my right ankle bone. My stride is heavier and slightly out of kilter. There is no pain. An MRI revealed a loss of fluid in the lowest disc in my back. A neurologist told me he believes the bulging disc has narrowed the passageway through which nerve signals travel to my left leg. What is your opinion of that analysis? Why can’t I find any other runners with this problem? If he is correct, what can I do? I would hate to resign myself to running permanently with this off-balance stride, which will limit my mileage and cause further injury.

Barry Bradley

Washington, DC

ANSWER:

At age 55, it is typical for an MRI scan to reveal degenerative, or age-related, changes, which include loss of fluid and/or bulging of one or more spinal discs. An MRI is actually not the best type of scan to demonstrate the bony canal through which the spinal nerves pass; a CT scan would be better. However, you probably don’t need to undergo a CT scan—an EMG can evaluate whether your spinal nerves are functioning normally.

Usually, if there is a problem involving a spinal nerve, there are symptoms of pain, as well as sensory symptoms such as numbness, tingling, or “pins and needles,” none of which you mentioned. Alternative explanations for your left leg weakness would include deficient circulation to the leg, though that would be very unusual for a long-time marathoner, especially assuming you don’t smoke. Your doctor can evaluate this by feeling how strong the arterial pulses are in your feet, and if there’s any uncertainty, further evaluation with a test involving blood pressure cuffs around your legs. This will determine blood pressure in each leg, compared to blood pressure in your arm, and can be done both before and after running. 

Other possibilities include problems with your nervous system at a level above your lower back, such as middle back, neck, or even brain. A complete neurologic examination, which includes evaluation of both upper limbs as well as your neck and head, would help determine whether you need an MRI scan of the middle spine and neck, an EMG of the upper body, or other testing. 

If one of the spinal nerves going to your left leg is somehow causing the symptoms, nonsurgical options are usually tried first. Specific stretching and strengthening, as well as postural, exercises would be recommended and performed under the supervision of a sports medicine physician or therapist. Anti-inflammatory medication may be recommended, either oral or by injection depending on whether your MRI scan showed anything more than just disc dehydration.

Brian L. Bowyer, MD

Columbus, OH