Multiple Sclerosis and the Loss of Proprioception

Nerve impairment affects balance and spatial awareness

Physical therapist doing a neurological exam with a young boy.
A physical therapist conducting a neurological exam with a young boy. Microgen/Getty Images

People with multiple sclerosis (MS) will be familiar the various exams a doctor will use to evaluate the neurological symptoms of the disease. In one, you may be asked to touch your nose with alternating fingers. In another, you would need to walk heel-to-toe in a perfectly straight line.

One of the tests people sometimes fail requires you place your feet together, extend your arms in front of you, and close your eyes.

As simple as this may sound, people will often find themselves nearly toppling over the moment their eyes are shut. What they've experienced is not clumsiness or a sudden bout of dizziness. It is a sensory effect known as Romberg's sign, or the loss of proprioception.

Understanding Proprioception

Proprioception is your ability to determine where you are in space in the absence of vision. It is based on sensory input from the joints and muscles. It is your awareness of your posture, weight, movement, and position of your limbs, both in relation to your environment and to other parts of your body.

Proprioception, which some people like to refer to as our "sixth sense," is an ability we often take for granted. What most of us fail to realize is how important it is to our mobility and spatial awareness, arguably as much as sight, touch, or hearing.

How Proprioception Is Affected in MS

MS disrupts communications between the central nervous system (involving the brain and spinal cord) and the peripheral nervous system (covering the rest of the body) through a process known as demyelination.

This happens when the protective covering of nerve cells is gradually stripped away, leading to the development of scar tissue (lesions).

Because proprioception requires instant and coordinated communication between these systems, MS can leave us a little less "in touch" with our sensory responses. Often times, the loss of balance is due to the disruption of nerve impulses from our ankles, our primary source of sensory feedback for balance, to the brain.

In addition to balance, we use proprioception to walk, eat, and pick up objects. When impaired, we can lose the ability to navigate spaces, play sports, or even drive.

Sensation and movement are inextricably linked. While the complete loss of proprioception is virtually impossible (given that we receive sensory information from all of our muscles and nerves), impairment of any sort can be unnerving and sometimes even debilitating.

Treating the Loss of Proprioception

Balance training is often used for people with MS to enhance the three sensory systems responsible for balance: proprioceptive, visual, and vestibular (inner ear). Since MS can affect one or more of these systems individually, therapists need to identify what, if any, role each part plays.

One of the frustrating aspects of the intervention is that some people improve their balance while others do not, often because the causes can be so far-ranging and diverse.

The location of MS lesions is usually key to understanding the problem. For example, the loss of fine touch and proprioception (known as dissociated sensory loss) is usually caused by a lesion on a single tract of the spinal cord. Any impairment of vision, meanwhile, is usually related to the development of lesions on the cerebellum or brain stem.

Similar, problems with postural control (the ability to maintain an upright posture) are usually related to lesions on the brain stem affecting the vestibular system.

By addressing and integrating all of these sensory factors into balance training, therapists are more likely to achieve positive results in persons with MS.

Sources:

Aman, J.; Elangoven, N.; Yeh, I.; and Konczak, J. "The effectiveness of proprioceptive training for improving motor function: a systematic review." Frontiers of Neurological Science. 2014; 8:1075.

Hebert, J.; Corboy, J.; Manago, M.; and Schenkman, M. "Effects of Vestibular Rehabilitation on Multiple Sclerosis–Related Fatigue and Upright Postural Control: A Randomized Controlled Trial." Physical Therapy/Journal of The American Physical Therapy Association. August 2011; 9(8):1166-83.

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