Effects of limb immobilization on brain plasticity.
Langer N, Hänggi J, Müller NA, Simmen HP, Jäncke L. Neurology. 2012 Jan 17;78(3):182-8.
In sports medicine a large variety of injuries require a period of immobilization that reduce or eliminate external load to protect healing structures. However, there are several consequences resulting from longer periods of immobilization including increased joint stiffness, muscle atrophy, and decreased motor control or coordination. These consequences may limit the amount of time a joint is immobilized and they also dictate our goals in rehabilitation after immobilization. However, one area of the body that has not been well examined for adaptations due to joint immobilization is the brain. The brain is thought to be one of the most adaptable structures of the body with previous animal studies demonstrating neural brain map changes with learning and movement tasks within several weeks. However it is not known if the reduced motor and sensory input caused by joint immobilization will lead to neural brain map changes or the amount of time required for these changes to occur. Therefore, Langer et al. longitudinally examined the structural changes of the gray and white matter of the brain in 10 patients receiving unilateral upper limb immobilization of their dominant (right) arm for at least 14 days. The nondominant (left) arm of patients was examined with the Motor Performance Series (MLS) test, which evaluates fine motor control, prior to immobilization and after an average of 16 days of immobilization of the dominant (right) arm. In addition a structural magnetic resonance imaging scan was taken at both time points to evaluate the surface morphometry (shape) of the brain and spinal cord. They found that there was a significant improvement in the MLS scores for the nondominant (left) arm following immobilization of the dominant (right) arm. There was also a decrease in gray matter thickness of the left primary motor and somatosensory area as well as a decrease in the white matter of the left corticospinal tract. The left hemisphere of the brain corresponds to the right side of the body. The increase in skill of the nondominant arm was found to be correlated with an increase in gray and white matter on the right side of the brain.
These are very interesting findings that suggest adaptations to stress (either deprivation or increase use) occur in more than just the most commonly thought structures (bones, tendons, ligaments, and muscles). Often times during the treatment or rehabilitation of orthopaedic injuries, the brain is not even on our minds (pun intended!). This study demonstrates immobilization can affect the neural centers of the brain thereby affect motor control to that joint. It is also very impressive that only a short duration of time (16 days) was required to cause significant structural changes in the brain. As clinicians we should keep this in mind and try to minimize the length of immobilization, if possible, to allow for a speedy recovery back to competition. Longer immobilization will allow the neural center of the brain for that joint to be taken over by other areas potentially including the other extremities. You can use the phrase “use it or lose it” to describe the way the brain adapts. Prolonged immobilization will increase rehabilitation time and may even decrease the athlete’s skill in the short term. This study also creates many more questions that should be answered with future research. Does low level isometric muscle contractions minimize this effect? Can electrical stimulation during immobilization also minimize this effect? Does it take longer to restore normal neural brain centers after re-mobilization compared to the loss?
Written by: Stephen Thomas
Reviewed by: Jeffrey Driban
Langer N, Hänggi J, Müller NA, Simmen HP, & Jäncke L (2012). Effects of limb immobilization on brain plasticity. Neurology, 78 (3), 182-8 PMID: 22249495