The Vestibular System

The Vestibular System, which is a contributor to our balance system and our sense of spatial orientation, is the sensory system that provides the dominant input about movement and equilibrioception. Vestibular sense provides information related to movement and head position. The vestibular sense is important for development of balance, coordination, eye control, attention, being secure with movement and some aspects of language development.

The vestibular system is composed of the vesibular receptors in the inner ear, the connections between them and other areas in the central nervous system.Together with the cochlea, a part of the auditory system, it constitutes the labyrinth of the inner ear, situated in the vestibulum in the inner ear (Figure 1). As our movements consist of rotations and translations, the vestibular system comprises two components: the semicircular canal system, which indicate rotational movements; and the otoliths, which indicate linear translations. The vestibular system sends signals primarily to the neural structures that control our eye movements, and to the muscles that keep us upright. The projections to the former provide the anatomical basis of the vestibular – ocular reflex, which is required for clear vision; and the projections to the muscles that control our posture are necessary to keep us upright.

Vision is an important component of the vestibular system. About twenty percent of visual neurons respond to vestibular stimulation (e.g. when spinning, head shaking, or rocking).   Adults who have suffered damage to the vestibular organs of the inner ear can learn to depend on visual information to maintain their balance.  However, If that visual information is removed or distorted (e.g. in the dark or when there is conflicting visual information about the horizon as when standing on a balcony), the individual will feel as if they are drifting or falling.

The auditory system is also highly involved in vestibular functions. The vestibular and auditory nerves join in the auditory canal and become the eighth cranial nerve of the brain.  Anything that disrupts auditory information can also affect vestibular functioning.   Blocked eustachian tubes in the inner ear, for example, create mild balance problems.

There are also other systems that provide sensory information to the vestibular system. The hands and fingers, for example, send information to the brain about the relationship between the body and stationary surfaces in the environment.  If the brain loses information from the vestibular organs of the inner ear (e.g. when there is fluid in the eustachian tubes) balance can be maintained by simply touching a vertical or horizontal surface with the fingertips.

The pressors on the soles of the feet provide important information to the vestibular areas of the brain about the texture of the ground.  This information is used to calculate weight and posture adjustments that will allow upright balance and movement.

Dysfunctions in the vestibular system can cause anxiety, nausea, a need for self-stimulation, abnormalities in muscle tone, academic problems, etc.

SIGNS OF VESTIBULAR DYSFUNCTION:

1. HYPERSENSITIVITY TO MOVEMENT (over-responsive):

__ avoids/dislikes playground equipment; i.e., swings, ladders, slides, or merry-go-rounds

__ prefers sedentary tasks, moves slowly and cautiously, avoids taking risks, and may appear “wimpy”

__ avoids/dislikes elevators and escalators; may prefer sitting while they are on them or, actually get motion sickness from them

__ may physically cling to an adult they trust

__ may appear terrified of falling even when there is no real risk of it

__ afraid of heights, even the height of a curb or step

__ fearful of feet leaving the ground

__ fearful of going up or down stairs or walking on uneven surfaces

__ afraid of being tipped upside down, sideways or backwards; will strongly resist getting hair washed over the sink

__ startles if someone else moves them; i.e., pushing his/her chair closer to the table

__ as an infant, may never have liked baby swings or jumpers

__ may be fearful of, and have difficulty riding a bike, jumping, hopping, or balancing on one foot (especially if eyes are closed)

__ may have disliked being placed on stomach as an infant

__ loses balance easily and may appear clumsy

__ fearful of activities which require good balance

__ avoids rapid or rotating movements

2. HYPOSENSITIVITY TO MOVEMENT (under-responsive):

__ in constant motion, can’t seem to sit still

__ craves fast, spinning, and/or intense movement experiences

__ loves being tossed in the air

__ could spin for hours and never appear to be dizzy

__ loves the fast, intense, and/or scary rides at amusement parks

__ always jumping on furniture, trampolines, spinning in a swivel chair, or getting into upside down positions

__ loves to swing as high as possible and for long periods of time

__ is a “thrill-seeker”; dangerous at times

__ always running, jumping, hopping etc. instead of walking

__ rocks body, shakes leg, or head while sitting

__ likes sudden or quick movements, such as, going over a big bump in the car or on a bike

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