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Home , Vestibular system

The Vestibular

The Vestibular Sense

David Brown continues with his series of articles highlighting some of the less well-known

Function ur other sensory the Vestibular system is not Most importantly, Ayres systems provide working then these other declared that the Vestibular Oinformation about two senses (vision and sense plays a key role in ourselves or about the ) can, with helping us to develop environment around us, great conscious effort, be effective self-regulation but the Vestibular system made to compensate to some of our arousal level, our is unique in providing extent and provide a degree ability to maintain a calm a continuous flow of of postural control and but alert state. So this is a information about the ‘fit’ security. sensory system that plays between the two, the person Two writers give interesting an extremely important role and the environment; it broader perspectives on this in enabling us to do almost tells a person how they sensory system that really everything that we do in our are interacting in the emphasize the great extent daily lives, and yet very few environment and it enables of its contribution to all of people know about it. In the individual to remain our functioning: sensory terms, this is the big oriented in space and in time. “In the final analysis, one one. This is the sense that tells may have a well-developed us about the position of our sensory map of the external So this is a sensory system that heads in relation to the pull world and a well-developed “ of gravity, it tells us which motor map of movement plays an extremely important way is ‘up’, and it detects from one place to another, motion. As a consequence of but if one does not know role in enabling us to do almost this it monitors and directs where they are with respect muscular activity and body to that map, they are virtually everything that we do in our position to maintain secure incapable of using that and functional postures spatial mapping information. daily lives, and yet very few whatever we are doing, And the Vestibular system people know about it. working very closely with the appears to be the system that ” touch and proprioceptive gives information about the senses. It also has very close individual’s location in the links with the visual sense, overall spatial map” Structure in particular stabilizing the (neurologist S.J. Cool in The Vestibular apparatus fixation point of the eyes 1987). shares space in the inner when the head moves which Jean Ayres, an occupational with the , which is enables us to maintain a therapist and the creator of part of the . stable visual image of the Sensory Integration Theory The Vestibular apparatus world as we move. Since and Therapy, is more concise is divided into two sets the Vestibular system only and states simply that: of receptors to monitor provides information about “The Vestibular system the two different kinds of the position and movement is the unifying system. All head movement, angular of the head it relies on well- other types of sensation are acceleration (which happens integrated links with the processed in reference to this when we shake or nod senses of proprioception and basic Vestibular information. our heads, bend over, or vision to facilitate postural The activity in the Vestibular roll over in bed) and linear adjustments in the rest of system provides a framework acceleration (which is what the body. If, for any reason, for the other aspects of our happens when we are in an experiences.”

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elevator moving up or down sent by the semicircular activated by your head or in a car moving forwards). canals on the other side of movements. But if you keep Let’s look at these two sets of the head, then the brain your head absolutely still and receptors. gets confused about what somebody else keeps moving the head is doing and the the book around in front of The semi circular resulting conflict will lead you it is impossible to read canals to of and along the lines of print since . your are First the semicircular canals. not being activated by any There are three of these in head movements, and your each , arranged at The vestibulo-ocular voluntary eye movements are right angles to each other so (VOR) totally incapable of keeping that they meet up in just the As they monitor all pace with the movements of same configuration that two movements of the head, the lines of print in the book. walls and the floor meet in the semicircular canals also This gives you a small idea the corner of a room. These organize compensatory of what it must be like to angles correspond to the movements of the muscles try to use your vision when three planes in which we that control eye movements, the semicircular canals are so that the fixation point of damaged in some way. For many children with the eyes remains on a stable base rather than moving “ The utricles and the deafblindness, especially about the same as the head; specific head movements children with CHARGE trigger specific semicircular The other set of receptors canals to activate specific in the Vestibular system are syndrome, all three of these pairs of eye muscles in two sack-like structures called specific ways that enable the utricles and the saccules. sensory systems are likely this. This is a remarkably The utricles lie horizontal complicated but quick when the head is upright and to be missing, impaired, or acting reflex sequence. they detect linear motion in malfunctioning. The amazing thing is that the horizontal plane, while ” although it stabilizes our the saccules lie vertical in visual fixation for us, we can the upright head and they move (horizontal, vertical, then superimpose voluntary detect movement up and and on the diagonal), so eye movements upon this down and forward and back. each of the three semicircular stable base whenever we These two pairs of organs canals is designed to detect wish to. This compensatory keep us vertically oriented motion in a single plane. reflex, complex and smooth with respect to gravity, Their job is to detect angular and rapid, yet something and any movement away acceleration of the head that we don’t need to think from upright triggers the and by acting together as about at all, is called the head-, which two matching sets, one left vestibulo-ocular reflex. You leads to correcting postural and one right, they tell our can identify the reflex at work adjustments. When we think brains exactly what position with a simple experiment. we are standing quite still our head is in at all times, If you hold a book very still and vertical we are, in fact, and what direction it is and try to read part of it as rocking very slightly back and moving. The matching sets of you move your head side to forth or side to side in order Vestibular apparatus on each side and up and down and to trigger this reflex to help side of the head are designed round in circles, it might not us to maintain correct vertical to work together, of course. be particularly comfortable, posture. If infection or damage causes but it is perfectly possible to the semicircular canals on keep your eyes reading and The Equilibrium Triad one side of the head to send following the lines of print, Postural and gravitational the brain information that thanks to your semicircular security, and a good disagrees with information canals which are being sense of equilibrium, both

18 • DbI Review • Ja n u a r y – Ju n e 2007 The Vestibular Sense depend upon the effective development and functioning We could see that problems were of three different but “ interdependent sensory central to learning disorders, but we needed to look systems (an “Equilibrium beyond vision. Triad”), namely the vision ” sense, the Vestibular sense, and the combined tactile/ proprioceptive senses. which can result in feelings once the child is standing For many children with of nausea and . and walking independently. deafblindness, especially l Blindness, low-vision Jean Ayres realized a long children with CHARGE and visual time ago that knowledge syndrome, all three of these difficulties. of Vestibular function was sensory systems are likely l Lack of use resulting from crucially important when to be missing, impaired, movement difficulties, from considering a child’s visual or malfunctioning, which feelings of insecurity and difficulties. In 1981 she wrote largely explains the slow fear, or from a generally that as early as the mid-60s: development of large motor low level of motivational “We could see that visual skills and mobility, but also drive due to limited processing problems were makes it remarkable that stimulation, limited sensory central to learning disorders, so many of these children perception, or ill health. but we needed to look do eventually stand up and Like all sensory systems, if beyond vision. If you just look walk. The good news is that the Vestibular sense is not at children from a behavioral any input and experience stimulated, challenged, and standpoint and do behavioral that helps to improve the used it will not develop type research and modeling, functioning of any of the effectively. you’ll never really discover sensory systems in this that a main foundation Equilibrium Triad can, The Vestibular sense to is the therefore, be regarded as Vestibular system, with making a contribution to and deafblindness proprioception and other the development of good When we look at the list senses also contributing.” postural control that might above it is possible to She went on to discover result in independent imagine that many children more about the central standing and walking – it is with deafblindness will importance of this sensory not only about the Vestibular have difficulties with their system that we all need to sense. Vestibular perception, either study and understand if we because of malfunctioning are to work successfully with Why does the or absence of the Vestibular children with deafblindness. Vestibular sense go apparatus (as is common Here are some of the with CHARGE Syndrome, wrong? important connections: for example), or because of l A damaged, or missing, other issues that are on the Vision Vestibular system. list. Because the Vestibular So there are strong links l Cerebral palsy and other apparatus plays a crucial between the Vestibular sorts of brain damage role in organizing sensory sense and vision, as already which result in abnormal perception through all the explained. Problems with muscle tone, limited other sensory channels this Vestibular perception may movement abilities, and problem has a profound affect the ability to maintain problems with tactile and effect on all areas of a stable visual field, but it proprioceptive perception. functioning and behavior for may also make it difficult to l Certain infections, the entire life of the child. follow objects smoothly with medications (and alcohol!). However, its importance and the eyes as they move, and l Over-stimulation (for impact is usually over-looked to differentiate whether it example, ), and under-played, especially

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is the object or oneself that example corners, the edges of these) should be very is moving. Some children of windows, doors, table helpful. Difficulties processing may appear to ‘go blind’ if tops, and wall-mounted auditory input contribute their postural security is too pictures). They may have to problems with language challenged, but they may much less equilibrium development, and also to surprise us by showing some outdoors where these strong problems with memory and well-developed visual (and visual markers are largely with learning many basic other) skills once they are absent or beyond their range academic skills. We all need flat on their back or on their of vision. One result might be to move to some extent in side on a stable surface. This a reluctance to go outdoors, order to listen, but children apparent paradox shouldn’t for example during recess at with Vestibular problems may surprise us because Jean school, and another might need to move even more to Ayres told us a long time ago be an inability to perform listen and to understand, so that, after air to breathe, certain tasks when they are that, when they are standing, postural security is our next outdoors that they perform telling them to “Stand still most urgent priority; without very well indoors. For children and listen” could be counter- postural security none of us is who are reading, the use productive. Understanding going to focus our attention of a typoscope (a letter-box and remembering visual and on reading a magazine, or on shaped frame) can help movement sequences are also listening carefully to a radio by isolating one single line likely to be more challenging broadcast, or on carrying of text at a time. Similarly, if the Vestibular sense is out a complex fine motor the use of large print on significantly impaired. task like sewing or writing. a computer might be very First we save ourselves from helpful to a student, not Memory falling, or reorganize our because their visual acuity is An absent Vestibular sense position to get more secure poor but because they need is likely to have a negative and physically comfortable, help to isolate the line of impact on the development and then we do our reading text on which they should be of memory, which, with the or listening or sewing. As visually fixating. difficulties with the effective they get older, children In addition to vision, use of vision (especially fine may use residual vision to the Vestibular sense links central vision), and with help them to stay upright with many other areas of the processing of auditory (think about the Equilibrium functioning: input, will have a cumulative Triad), compensating for impact on speech and having a poor Vestibular and language development, and sense by using the strong understanding on receptive understanding visual impressions made by sequencing of visual language (for horizontal and, especially, example sign language, vertical lines in a room (for There are links between the Vestibular sense and the finger spelling, written ability to process sound, language). Resultant to perceive and remember difficulties with expressing A truly collaborative approach auditory sequences, and so themselves, or the constant “ to develop spoken language. experience of having their that brings together a teacher of For children with Vestibular expressive communications issues this has implications misinterpreted, can lead the deaf, a speech therapist, and in addition to other hearing some children to give up, or to resort to explosive an occupational therapist trained difficulties, and a truly collaborative approach that behaviors that may be in Sensory Integration Therapy (or brings together a teacher of construed as unpredictable, the deaf, a speech therapist, irrational, or emotionally any combination of these) should and an occupational therapist disturbed. Significant trained in Sensory Integration problems with the Vestibular be very helpful.” Therapy (or any combination sense can also inhibit the

20 • DbI Review • Ja n u a r y – Ju n e 2007 The Vestibular Sense development of effective children walk with repeating Breathing/ feeding body language, since postural swaying circular movements skills/digestion and control, equilibrium, muscle of the upper body and nutrition tone and head, as if trying to keep will all be impacted. aware of the danger areas Because of resultant low at the limits of safe posture tone, poor head control, preferred horizontal postures, Attention/ distraction by alternating from one and limited movement, these and levels of arousal ‘danger’ position to another. On-going monitoring are all likely to be adversely If arousal levels are by a physical therapist is impacted. abnormally high or low, and important because there is a the child has very limited high risk of the development Sociability ability to self-regulate of neuromuscular scoliosis As can be seen from this because of problems with the (curvature of the spine) in list, significant difficulties Vestibular sense, they may childhood and the teenage with the Vestibular sense never attain that ‘calm but years. cause disorientation and alert’ state that is essential confusion in most aspects for effective learning. Bilateral coordination/ of daily living, particularly when there are other sensory Muscle tone/ postural orientation and mobility impairments present also. control and security Unless people involved with Very persistent low muscle Bilateral coordination, the the child are prepared to tone is often associated with ability to use both left and understand these difficulties severe Vestibular problems. right sides of the body and adopt a supportive and Low tone is also associated independently and also non-judgmental attitude, with low vision, breathing together, may be significantly then the child is likely to difficulties, and generally affected, with one side so develop a strong distrust reduced sensory inputs, dominant that the other and dislike of others. This is hence reduced perceptual side of the body is ignored. especially regrettable when . The problem Hand dominance and eye people repeatedly stop the is then compounded by dominance may be very child doing the very things the lack of motivation to late developing, or one that enable them to function move and the resulting lack hand and eye might be so – things like adopting of “exercise.” Protective dominant that the child specific postures or using reactions, standing, cruising, is effectively functionally self-regulation strategies that and independent walking one-eyed and one-handed. are interpreted negatively as usually develop very late. Remember also that, when it ‘self-stimulating behaviors’. When children do walk, there is working effectively, this is is often a characteristic gait, the sense that tells a person What can we do to how they are interacting in some aspects of which may help? remain evident for many the environment, enabling l Respect compensatory years – the feet spaced widely them to remain oriented in behaviors as functional, apart, the knees bent to space and in time. Add these and help the child to make lower the center of gravity, challenges to blindness, and their own choices. Prohibit the body rolling from side to poor body awareness anything dangerous, of to side with each step, the due to limited tactile and course, but otherwise do feet sliding along the floor proprioceptive feedback, and not attempt to remove or planted down very firmly it seems amazing that many or replace any of these on the floor with each step children with deafblindness compensatory behaviors (maybe several times, almost do manage to learn and until their function has like patting the floor with the remember routes at all. been established. foot), and the arms held up l Suggest evaluation like a tightrope walker. Some by an occupational therapist (preferably

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direction of movement, the whole body and Think about the total demands and providing adequate all its sensory systems. “ physical support for both Some older children and made on the child by every the head and the limbs teenagers can seem to during movement as well function quite well at their activity in every situation as for the child’s body. desk for extended periods (in other words, think l Always make appropriate of time, but they then need physical support available periodically to get up and multi-sensory). (for example, seating, move around, or to get ” a table, things to lean into a horizontal position against, or you yourself). to relax and to re-charge trained in Sensory As these children get older their energy levels for the Integration Therapy) the problems with fatigue, next exertions. They may and a physiotherapist, postural control, and sitting also need periods in the and implement their or standing unsupported horizontal position to suggestions. Regular input may be less evident but reorganize their sensory from therapists is very still present. Sometimes systems using behaviors like important for all children the student will benefit leg kicking, hand flapping, with Vestibular dysfunction, from using an adapted shoulder shrugging, but these therapists will chair, with arms and a hyperventilating, or gazing need to be informed about footrest, possibly also with at bright light. the existence of severe the seat tilted forwards l Observe for indications problems and to encourage more active of under-arousal or over- about the implications of sitting against gravity. arousal and know what this. Alternately, some children to do about it (if the child l Pace activities to facilitate may benefit from provision cannot do this themselves). optimal functioning and to of mobile seating such as l Think about the total minimize fatigue and stress. a suitably sized therapy demands made on the child Functioning with little or no ball, which can facilitate by every activity in every Vestibular information is an repetitive rhythmic motion situation (in other words, extremely challenging and of the lower trunk and think multi-sensory). Many tiring business, so breaks legs which helps the brain otherwise well planned and rest periods may to know where the body activities fail because the need to be frequent and is and that it is all secure child is being challenged extensive. and under control (rather or distracted by a sensory l Remember that work that like the way we all sway challenge that has not improves the functioning around slightly when we been noticed by the adults of other sensory channels think we are standing quite involved with them. can help to ameliorate still). There may still be a l Isolate lines of text (for the impact of Vestibular great need to support the example, large font on difficulties. head by propping it up screen, typoscope) if l Younger children, and those or by resting it on one or necessary. with physical disabilities, both arms or even down may need to be lifted and on the desktop itself, in David Brown carried, which could be order to read or write. Also (Education Specialist) very threatening for them remember that extended California Deaf-Blind if they have poor Vestibular periods standing still and Services, 1600 Holloway / functioning combined with entirely unsupported Pacific Plaza other sensory impairments. are usually particularly San Francisco, Handle them to minimize challenging. CA 94132-4201 stress, for example, l Allow periods of movement Tel: 415-405-7559 by using consistent or repose, as appropriate, FAX: 415-405-7562 anticipation cues, using for reorganization of E-mail: [email protected] an appropriate speed &

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