Vestibular

The Vestibular System and Sensory Integration Dysfunction and How They Relate to Deafness

By Melissa K. Chaikof (Rachel’s and Jessica’s Mom)

Parents of deaf babies often write into the CICircle listserv expressing concern about their babies’ and toddlers’ unusual behaviors, including arching their backs, bobbing their heads on their parents’ shoulders, overall poor head control, late crawling, sitting, walking and poor balance. If they mention these concerns to their pediatrician, they’ll often get questionable diagnoses including possible cerebral palsy or even my favorite, “an amazing collagen vascular system.” When they’re older, they may also receive the inaccurate diagnosis of ADHD. In fact, none of these are usually the case. The culprit, instead, is the vestibular system, a system little understood by most but sometimes deemed the sixth sense by neuroscientists.

Many of those who are deaf also suffer from vestibular dysfunction because, when the cochlea suffers damage, so does the vestibular system because, together with the cochlea, it is located in the inner ear, tucked into the temporal bone, the large irregular bone on either side of the head that contains the inner ear. It was as recently as the 19th century that the vestibular system was even recognized as separate from the auditory portion of the inner ear. Some of the known causes of deafness that either often or always also cause vestibular dysfunction are Usher Syndrome, Waardenburg Syndrome, CHARGE Syndrome, Cytomegalovirus (CMV) and Enlarged Vestibular Aqueducts (EVA).

What Is the Vestibular System?

The first sensory system to fully develop by six months after conception is the vestibular system. The vestibular system tells us where our heads and bodies are in space. This system takes in sensory messages about balance and movement from the neck, eyes, and body, sends these messages to the central nervous system for processing, and then helps generate muscle tone that allows us to move smoothly and efficiently. Directly or indirectly, the vestibular system influences nearly everything we do. It is the unifying system in our brain that modifies and coordinates information received from other systems. The vestibular system functions like a traffic cop, telling each sensation where and when it should go or stop.

The vestibular system contributes to our balance and sense of spatial orientation. All of our movements are either side-to-side or circular, and, thus, the vestibular system contains two components, the semicircular canal system, which indicates circular movements, and the otoliths, which indicate side-to-side movements. Each time we move our head, there is a corresponding movement of the fluid in the vestibular system of each ear that allows each ear to sense how far our head has moved and at what speed.

A recent New York Times article provided an interesting example of the vestibular system at work.

“If you want to glimpse the handiwork of one of your body’s unsung sensory heroes, try this little experiment. Hold your index finger a few inches in front of your face and sweep it back and forth at a rate of maybe once or twice a second. What do you see? A blurry finger. Now hold your finger steady and instead shake your head back and forth at the same half-second pace. This time, no blur. … The finger stays in focus even as your head vigorously pantomimes its denial.”

The reason for this difference is that the brain distinguishes between movements of the viewer vs. movements of the view. Because the brain can make this distinction, we are able to walk without having our surroundings appear to blur or lurch. Unlike hearing or vision, which we can easily understand by closing our eyes or plugging our ears, appreciating the significance of the vestibular system is more difficult. When it is functioning properly, we are unaware that it is working because it integrates with other sensory information.

Vestibular Dysfunction

According to Carol Stock Kranowitz in her book, The Out-of-Sync Child, “the vestibular system seems to ‘prime’ the entire nervous system to function effectively. When the vestibular system does not function in a consistent and accurate way, the interpretation of other sensations will be inconsistent and inaccurate, and the nervous system will have trouble ‘getting started.’”

The vestibular system does more than simply allow us to stand upright, maintain balance and move through space. As mentioned earlier, it is like the traffic cop and coordinates information from the not just the inner ear but also the eyes, muscles, joints, fingertips, palms of the hands , soles of the feet, jaw and gravity receptors on the skin. In addition, it helps adjust the heart rate and blood pressure, muscle tone and limb position.

Vestibular dysfunction is the inefficient processing of sensations perceived through the inner ear. Dysfunctions in the vestibular system can cause anxiety or panic attacks, a need for self-stimulation, abnormalities in muscle tone, academic problems, drooling, etc. Children with vestibular dysfunction are inefficient at integrating information about movement, gravity, balance and space. As a result, they can be over sensitive or under sensitive to movement. They may not develop the necessary postural responses to sit upright and, instead, slump when sitting. They may never crawl and may learn to walk late. As they grow older, they may appear uncoordinated, awkward and clumsy. They may fall and trip easily, bump into things when they move, and easily lose their balance when they are slightly off their center of gravity.

School age children with vestibular dysfunction may become confused when looking up at the board and then back down at their desk. Reading problems may arise from the difficulty to track left to right. Language processing can also be an issue, as can memory retrieval and a decreased sense of internal certainty, that is, the ability to see the big picture or to reach a point of closure or to see the proverbial forest through the trees.

In her book, The Out-of-Sync Child, Carol Stock Kranowitz addresses six specific areas in which children with vestibular dysfunction may experience difficulty, movement and balance, muscle tone, bilateral coordination, auditory-language processing, visual spatial processing and motor planning.

Movement and Balance

When the central nervous system connects signals from the vestibular system with other sensations, we are able to coordinate our bodies and move seemingly automatically. Our vestibular system tells us which way is up and that that is where we want to be. In order to remain upright, we make unconscious physical adjustments that allow us to stabilize our bodies, maintain our balance and move smoothly. Children with vestibular dysfunction have difficulty with movement and balance. They may move too little or too much, and their resulting movements are awkward and uncoordinated.

Muscle Tone

The vestibular system affects muscle tone by regulating neurological information from the brain to the muscles, telling them how much to contract so that we can resist gravity to perform skilled tasks. Thus, children with vestibular dysfunction may have low muscle tone and so appear to be loose or floppy.

Bilateral Coordination

The vestibular system helps integrate and coordinate both sides of the body. This is known as bilateral coordination. Usually, by the age of three or four, children have mastered the skill of crossing the midline. That is, they can move one hand, foot or eye into the space of the opposite hand, foot or eye. Preschool and early elementary activities, such as painting at an easel, catching and throwing a ball and reading from left to right are examples of activities that involve crossing the midline. Children with poor bilateral coordination may also appear not to establish a righthanded or lefthanded preference.

Auditory-Language Processing

The vestibular system affects auditory-language processing. Ordinarily, the auditory and vestibular systems work together to process sensations of sound and movement. Even the ability to hear sound, though, does not guarantee the ability to process it. Auditory processing skills include auditory discrimination, that is differentiating among sounds, auditory figure-ground, that is discriminating between foreground and background sounds, and, finally, language. Auditory processing problems that may arise as a result of vestibular dysfunction include detecting likenesses and differences in words, attending to the teacher’s voice in the presence of background noise, difficulty following directions, difficulty with expressive language and difficulty with auditory sequential memory.

Visual-Spatial Processing

Vision is not simply eyesight. While eyesight contributes to our visual skills, vision is a complex process that enables us to identify sights, to anticipate what is coming at us, and to prepare for a response. Four motor skills comprise our visual skills, and our vestibular system affects all four of them. They are

  • Fixation – Aiming our eyes or shifting our gaze from one object to another, such as when reading across a line and down a page
  • Tracking – Following moving objects easily and accurately, such as when catching a ball
  • Focusing – Switching our gaze quickly and accurately between near and distant objects
  • Binocular Vision – Integrating the images from our two separate eyes into one single mental picture

The vestibular system also affects spatial awareness, which is a part of visual processing as well because, in order to acquire this skill, we gain practice by moving around and participating in many sensory experiences. Some visual-spatial processing skills are visual discrimination, including symbols and forms, such as letters, numbers and words, visual figure-ground, which entails distinguishing objects in the foreground vs. those in the background, including a word on a page, and visual-spatial functions, which include form constancy, orientation, and directionality and are necessary to judge distances between objects and left and right. Children with vestibular dysfunction may mix up words on a page, skip words when reading, write letters backwards, have difficulty maintaining their place on a page when reading, have difficulty climbing stairs, have difficulty doing jigsaw puzzles, and get lost frequently due to a poor sense of direction.

Motor Planning

Proprioception refers to sensory information that provides us with information about our own body movement or body position. Motor planning refers to our ability to conceptualize, organize and realize a complex series of movements. When our nervous system integrates vestibular sensations with tactile sensations and proprioceptive sensations, we are able to motor plan. That is, we can do what we want our bodies to do. Motor planning affects not only skills such as throwing a ball, running or skating, but also talking. Consequently, children with vestibular dysfunction can have oral motor issues or speech apraxia.

What to Do about Vestibular Dysfunction
Vestibular dysfunction is not an insurmountable obstacle. Given time and the proper early intervention, children can learn to compensate for and overcome the difficulties that arise. Occupational therapy is the particular branch of therapy that addresses vestibular dysfunction. Occupational therapy today includes not only “treatment” in a therapy room, but also swimming and therapy on horseback, known as hippotherapy. Parents can also provide their children with activities at home to stimulate their vestibular system, such as swingsets and other toys that provide many opportunities for swinging and spinning.
Braintraining.com provides these suggestions:

  • Swinging, rocking, jumping
  • Rotating chair: The child sits in an office chair or other chair that can spin easily and is rotated up to 20 times, changing direction frequently.  Stop immediately if the child appears uncertain or if they want to get down from the chair. Children who are unstable can be placed in an adult’s lap and rocked side to side (slowly) rather than spun.
  • Visual Pursuit: Hold an object at eye level, a comfortable distance away from the child’s face and then move the object smoothly from the left to the right slowly while the child follows the object with the eyes alone. Change direction and move the target in all directions, increasing speed over time.
  • Balance:  The child walks up and down a low ramp while holding an adult’s hand. Increase the slope (rake) of the incline as the child improves. Sitting on balance balls can also be used to help improve balance, or standing on boards with a rounded bottom.
  • Obstacle Course.
  • Gaze Stabilization:  The child stands on an uneven, soft, or movable surface (e.g. foam, trampoline or tilt board) and focuses on a toy or interesting object that is moving either diagonally, horizontally, or vertically in front of them.  Change the trajectory, direction, and speed of the object movement as the child watches.
  • Targets and Optic Flow:  Play catch with balls of varying diameters and textures, increasing the distance between players over time.  If the child has difficulty catching a ball, use a balloon rather than a ball.  Increase difficulty by using smaller and harder balls to increase the speed and challenge of the game.
  • Steps, Curbs and Parking Blocks:  Practice walking smoothly up steps, curbs and parking blocks.

In addition, Carol Stock Kranowitz has written a companion book to The Out-of-Sync Child entitled The Out-of-Sync Child Has Fun. This book is a wonderful resource for parents of activities they can do at home with their children.

References:

  • Angier, Natalie. “The Unappreciated, Holding Our Lives in Balance.” The New York Times. 28 October 2008 http://www.nytimes.com/2008/10/28/science/28angi.html.
  • Auditory and Vesitibular Pathways.” < http://thalamus.wustl.edu/course/audvest.html>
  • “The Cause of Internet and TV Addiction?” < http://pages.prodigy.net/unohu/neuro_vest.htm>.
  • Cullen, Kathleen and Soroush Sadeghi. “Vestibular System.” Scholarpedia, 3(1):3013. < http://www.scholarpedia.org/article/Vestibular_system>.
  • Erickson, Kenneth M.D. “Cognitive Aspects of Vestibular Disorders.” Lecture delivered at Vestibular Disorders Association (VEDA) conference, Portland, Oregon.
  • Kranowitz, Carol Stock. The Out-of-Sync Child. New York. Perigee, 1998.
  • Vestibular Disorders Association. “Possible Symptoms of Vestibular Disorders.” http://www.vestibular.org/vestibular-disorders/symptoms.php.
  • “The Vestibular System.” http://www.braintraining.com/vestibular.htm.

Resources:

Websites:
American Occupational Therapy Association
Pediatric Therapy Network
Sensory Integration Dysfunction
Sensory Processing Disorder Foundation
The Vestibular Disorders Association (VEDA)

Books:
Biel, Lindsey and Nancy Peske. Raising a Sensory Smart Child: The Definitive Handbook for Helping Your Child with Sensory Integration Issues. 2005
Kranowitz, Carol Stock. The Out-of-Sync Child: Recognizing and Coping with Sensory Processing Disorder, Revised Edition. 2006
Kranowitz, Carol Stock. The Out-of-Sync Child Has Fun, Revised Edition: Activities for Kids with Sensory Processing Disorder. 2006

Sources for Products to Use at Home:
Integrations
PDP Products
Sensory Comfort
Sensory Processing Disorder
Southpaw Enterprises