Cognitive Challenges Effect Postural Balance in MS Patients: A New Study
Have you ever caught yourself swaying a bit while you were deep in thought and using your brain power to work something out? Do you trip just a little bit more when you walk and talk? MS might be to blame.
We know that balance control is affected by musculoskeletal and neuromuscular control (see What is the Romberg Test?). Deficits in balance/postural control can be related to impaired visual, vestibular, and somatosensory inputs to the central nervous system. Recent published research shows that balance control also has a cognitive component.
A small study undertaken at the Ahvaz Jundishapur University (Khuzestan, Iran) showed that MS patients tend to sway more when tasked with a cognitive challenge as compared to their healthy, age-matched controls under varying circumstances.
There were two group of patients included in this study. 23 MS patients (eight male and 15 female) who met the following criteria:
- (1) a definite diagnosis of relapsing-remitting MS
- (2) ability to stand unassisted for at least 30 seconds
- (3) ability to walk 100 meters independently
- (4) in remission.
The control group consisted of 23 healthy participants who were matched with the MS patients according to gender, age, height, body mass index, years of education, and cognitive ability. Patients (MS or healthy) were excluded if they had an Expanded Disability Status Scale (EDSS) score greater than 5.0 and/or a Mini-Mental State Examination (MMSE) score less than 24 (indicating cognitive impairment).
The participants were tested on a force platform which measured aspects of sway velocity, direction, and area. Think a Wii balance board. Testing results were compared between the two groups. Each participant was tested under seven conditions:
- (1) sitting in a chair to test postural control
- (2) standing on a rigid surface with eyes open (RO)
- (3) standing on a rigid surface with eyes closed (RC)
- (4) standing on foam surface with eyes closed (FC)
- (5) standing RO and dual tasked with a cognitive challenge
- (6) standing RC and dual tasked with a cognitive challenge
- (7) standing FC and dual tasked with a cognitive challenge
Closing the eyes removed the visual input helpful to maintain balance while standing on the foam surface took away somatosensory input. The cognitive challenge chosen was counting backwards by threes beginning with a random number between 100 and 200.
There was no difference in balance control between the MS patients and healthy controls under testing conditions #1 and #2 listed above. But significant difference in balance control was seen between groups under conditions #5, #6, #7 listed above.
When MS patients stood on the foam surface, closed their eyes, and counted backwards, they tended to sway a great deal in a front to back direction (anteroposterior). Healthy individuals did not experience the same increased sway velocity when visual and sensory input was removed.
I informally tested myself with my feet at a 30 degree angle and heels separated by 3 cm (just as in the testing protocol) and discovered that I experienced an increased sway from front to back similar to the MS patients in this study. Very interesting. When I am tested for the Romberg sign with my feet parallel and touching, my body tends to fall toward one direction and my hips will sway side to side.
When I was going to physical therapy regularly in 2009, it was for three reasons: (1) work on improving my deconditioned physical state, (2) improve my abnormal gait, (3) strengthen my proprioception skills. After some time when my condition had improved in each of these areas, my physical therapist would increase the challenges she presented. I remember how she would engage me mentally while we worked on balance exercises. Looks like she was helping me to improve my body’s ability to dual task, a skill similar to what was tested in this research study.
The authors of the study conclude that variability in sway velocity seems to confirm the different response to cognitive loading (the extra mental challenge presented) between MS patients and healthy participants. Also, dual tasking, in contrast to single tasking, had the ability to discriminate between the two groups under each of the postural challenges (ie. RC, FC, etc) presented.
Walking and talking, balancing and calculating, keeping your eyes off the ground...all challenges which might well be blamed (just a bit) on the MS. Have you noticed any change in your ability to stay balanced when you are faced with cognitive challenges?
Negahban H, et al. The effects of cognitive loading on balance control in patients with multiple sclerosis. Gait Posture (2011), doi: 10.1016/j.gaitpost.2011.06.023