Sensory Integration (Part 7) – The Vestibular System
The vestibular sense has an influence on:
- Hearing: speech and language development
- Muscle tone
- Bilateral integration
- Motor planning
- Gravitational security
- Emotional security
- Physical security
The vestibular system is regulated by two systems: the semi-circular canals and the otolith.
The vestibular system is activated by movement of the head (linear, angular or rotation), vibration and gravity. The hair cells in the semi-circular canals, in the inner ear, are activated by movement of the gel (cupula) due to rotary head movement. The Otolith is divided into the saccule and utricle. The saccule is sensitive to up-and-down movement of the head and the utricle to forward-and-backward movement, thus assisting us to orientate ourselves to the upright position.
Modulation & arousal level
Types of modulation difficulties: over-responsive to movement, gravitational insecurity, under-responsive to vestibular sensation and sensory-seeking behaviour.
Intolerance to movement (over-responsiveness)
It is hypothesized that it may be due to poor modulation of the input from the semi-circular canals.
The child usually present as follows:
- Dislikes swinging, spinning, sliding
- Moves slowly
- No risk-taking behaviour.
- May present as a wilful or uncooperative child
- Uncomfortable when moving e.g. elevators, escalators, driving in a car
- May experience nausea, dizziness or vertigo
- Loses balance easily and may appear clumsy (the teacher and her parents reported that VB appears clumsy)
- Fearful of activities that require balance
Postural insecurity was defined by May-Benson (May-Benson, 2007, p. 143) as extreme caution when a child is doing physical challenges, involving postural strength and stability, due to decreased postural ability.
It is hypothesized that it may be due to poor modulation of the input from the otolith system.
The child usually presents with an intense emotional reaction e.g.:
- Fear of falling
- Fearful of heights
- Anxious when feet leave the ground
- Fearful of climbing stairs
- Fearful when head is not in the upright position (VB. doesn’t like it when her head is tilted backwards)
- Fearful when moved (VB. was scared when moved passively – quick movements)
- Avoids new positions/postures
- Moves slowly and carefully
- Avoids riding a bike, jumping, hopping, standing on one leg
- Can swing / make circular movements for a long period of time without getting dizzy (the teacher reported this behaviour)
- Poor protective extension in arms and legs as she doesn’t notice that she is falling (this was observed during the clinical observation by the therapist and reported by the parents)
Sensory seeking behaviour
- Wants to move continuously
- Has trouble sitting still (VB. exhibits this behaviour according to the teacher and therapist)
- Shakes head
- Rocks back-and-forth
- Jumps up and down
- Craves intense movement
- Adrenaline junkie: risk-taking behaviour (According to the parents she exhibits this behaviour)
- Jumps on chairs, trampolines, spins in a swivel chair, gets into upside-down postures
- Loves to swing as high and fast as possible (The teacher reported this behaviour at school)
- Rather runs/jumps/hops instead of walking
- Likes sudden and quick movements