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. 

Results:

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.