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14/5/2015
1
THE VESTIBULAR
SYSTEM
(c) 2014 USC OS OT
LECTURE PREPARED BY
Diane Parham, PhD, OTR, FAOTA, 1999, revised, 2005, 2008, 2011
With input from Susanne Smith Roley OTD, OTR/L, FAOTA
OVERVIEW
Introduction
Structures and
functions
Development
Disorders in Children
Intervention
INTRODUCTION
Central role of vestibular system
Two systems: peripheral and central
INTRODUCTION
Peripheral vestibular
system = receptor organs
Located in inner ear
Sensitive to movement of
head, gravity, and
vibration
INTRODUCTION
Central vestibular system = multimodal CNS system
Integrated with vision & proprioception
Close linkages with cerebellar, reticular, &
autonomic systems
Functions cannot be completely isolated
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INTRODUCTION
General functions
Integrates sensations in brainstem
Awareness of body position relative to gravity
Posture and equilibrium
Antigravity muscle tone
Stable visual field
Physical and emotional security
INTRODUCTION
Relationship to occupation
Vestibular processing affects quality of life
Vestibular problems ���� problems with occupational
performance and satisfaction
INTRODUCTION
Types of Problems
Vestibular-bilateral problems: posture, balance, & bilateral
coordination affected
Hyper-responsive: gravitational insecurity (GI)
INTRODUCTION
Child with vestibular-bilateral problems
Infancy
Preschool
School-age
INTRODUCTION
Child with hyper-responsivity
Infancy
Preschool
School-age
INTRODUCTION
Effects on parents
Shaping of identity
Good response to intervention
Reframing -- Importance of parent & teacher education
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PERIPHERAL VESTIBULAR SYSTEM
Semicircular canals
Otolith organs
Canal superior
PERIPHERAL VESTIBULAR SYSTEM
Functional implications
Any head position or movement ���� vestibular stimulation
Canals & otolith organs ����reference point for spatial orientation
Macular information especially critical
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PERIPHERAL VESTIBULAR SYSTEM
Treatment considerations:
Body position & plane of movement
Speed or velocity of movement
Linear vs. angular movement
Change in velocity
CENTRAL
VESTIBULAR SYSTEM
Overview
Vestibular nuclei in brainstem
Descending pathways
Brainstem-level pathways
Ascending pathways
CENTRAL VESTIBULAR SYSTEM
Vestibular nuclei
Superior
Medial
Lateral (Deiter’s)
Inferior
CENTRAL VESTIBULAR SYSTEM
Descending Vestibulospinal Pathways:
Lateral vestibulospinal tract (LVST)
Medial vestibulospinal tract
(MVST)
Reticulospinal tract
CENTRAL VESTIBULAR SYSTEM
Descending Vestibulospinal Pathways:
Lateral vestibulospinal tr.
Medial vestibulospinal tr.
Reticulospinal tract
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CENTRAL VESTIBULAR SYSTEM
Functions of Descending (Spinal) Pathways:
Head righting and equilibrium reactions (transient & sustained)
Powerful autonomic effects
Proprioception modulates vestibular input
CENTRAL VESTIBULAR SYSTEM
Brainstem-Level Pathways:
Reticular formation
Vestibulocerebellar
pathways
CENTRAL VESTIBULAR SYSTEM
Ascending Pathways:
Vestibulo-ocular pathways
Reticular-limbic pathways
Vestibulo-cortical projections
CENTRAL VESTIBULAR SYSTEM
Vestibulo-ocular pathways:
Vestibular nuclei to ocular-motor cranial nerves
Mediate compensatory eye movements for stable visual field
CENTRAL VESTIBULAR SYSTEM
Vestibulo-ocular reflex (VOR):
Eyes move opposite to head movement
Doll’s eye reflex in newborn infants
Provides stable visual field
Enables visual fixation during head movements
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CENTRAL
VESTIBULAR SYSTEM
Vestibular nystagmus:
Induced by angular acceleration
Slow phase: same as VOR
Fast phase: eyes jerk or beat back toward midline
CENTRAL
VESTIBULAR SYSTEM
Two main types of vestibular nystagmus
Perrotary: During rotation
Postrotary: After rotation
CENTRAL VESTIBULAR SYSTEM
Perrotary nystagmus:
During rotation, eyes beat in direction of rotation
Postrotary nystagmus:
After rotation, eyes beat opposite to rotation
Direction may reverse for a few beats at the end (called secondary
nystagmus)
CENTRAL VESTIBULAR SYSTEM
More on Vestibular Nystagmus
Slow phase:
Velocity closely related to peripheral function
Fast phase:
Mediated by central mechanism in brainstem
CENTRAL VESTIBULAR SYSTEM
More on Postrotary Nystagmus (PRN)
Velocity storage in brainstem:
more rotation ���� longer duration of PRN
Unusually shortened duration of PRN suggests centralvestibular problem in brainstem
Duration also affected by arousal level & visual stimuli
CENTRAL VESTIBULAR SYSTEM
Influence of Vision on Vestibular System
Optokinetic reflex: visual system
Optokinetic nystagmus (OKN): induced visually
Optokinetic after-nystagmus (OKAN): pure central vestibular function
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CENTRAL
VESTIBULAR SYSTEM
Influence of Vision on Vestibular System
Vection
Powerful illusions regarding spatial orientation
CENTRAL
VESTIBULAR SYSTEM
Pathological types of nystagmus (not sensory-based):
Spontaneous
Positional
Gaze
Congenital
CENTRAL
VESTIBULAR SYSTEM
Functional implications of vestibular-visual connections:
Vestibular & visual work together to
mediate eye movements
Vestibular does not control all types of eye movements
PRN is not a pure vestibular measure
CENTRAL VESTIBULAR SYSTEM
Reticular-limbic pathways
Vestibular n. ���� reticular system ���� limbic system
Emotional responses to vestibular stimulation
Increased eye contact during vestibular stimulation
CENTRAL VESTIBULAR SYSTEM
Vestibular-cortical projections
Vestibular-visual-proprioceptive signals
converge in thalamus, parietal lobe, & somatosensory
transition zone
Prolonged postrotary nystagmus may be
characteristic of children with higher cortical dysfunction
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CENTRAL VESTIBULAR SYSTEM
Alain Berthoz (2002):
Anticipation of environmental conditions
& results of action,
combined with intentionand planning,
affects the sensitivity & interactions
among components of the central vestibular system
DEVELOPMENT OF
VESTIBULAR SYSTEM
Phylogenetically old system
Develops early in utero
Many primitive motor patterns (reflexes) mediated by
vestibular with vision or proprioception
DEVELOPMENT OF VESTIBULAR
SYSTEM
LVST matures at ~ 6 months postnally (Landau)
Vestibulo-ocular responses rapidly mature over the first year
PRN duration lengthens with age
ASSESSMENT OF
CHILDREN FOR
VESTIBULAR-BASED
PROBLEMS
Vestibular-based postural problems originally identified in
research with SIPT
Vestibular system may also be involved with modulation
difficulties
ASSESSMENT USING
UNSTRUCTURED
OBSERVATIONS
• Movement preferences
• Craving or avoiding body/head movement
• Seeking or avoiding visual movement
• Head/neck/eye control
• Head/trunk/limb control
• Response to movement: posture, alertness, attention, affect
• Presence of anxiety?
STRUCTURED OBSERVATIONS AND
STANDARDIZED TESTS
Clinical observations:
• Prone extension
• Tilt Board Reach (Fisher)
Some standardized tests, e.g., SWB on the SIPT
Pediatric Clinical Test of Sensory Interaction for Balance (Crowe et al., 1990; Deitz et al., 1991)
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ASSESSMENT
CONSIDERATIONS
Consider alternative explanations for difficulties
Vestibular processing problems may be secondary to
experiences, biomechanical factors, other disorders
INTERVENTION FOR
VESTIBULAR PROBLEMS
GENERAL GUIDELINES
Introduce vestibular activities early in Ayres SI intervention
Suspended equipment makes a big difference!
Gear to the needs, tolerance level, and preferences of child
Goal: an actively involved child who enjoys game
INTERVENTION FOR
VESTIBULAR DISORDERS
GENERAL GUIDELINES
Consider opportunities for varied input:
linear vs. angular, sustained vs.
transient, & slow vs. fast
Consider influences of vision & proprioception
Monitor closely for safety and overstimulation
INTERVENTION FOR VESTIBULAR
DISORDERS
GENERAL GUIDELINES
For overstimulated child:
use increased proprioception, preferably through active resistance
Manipulate visual environment:
visual targets to inhibitvestibular
dim lighting or bare walls to facilitate vestibular
VESTIBULOGENIC
SEIZURES
DO THEY EXIST?
Old concept of vestibulogenic seizures proposed but not validated--
Research shows no increase in seizure activity due to vestibular stimulation in seizure-prone children
But pulsating light is a common trigger of seizures – so be careful with lighting in the room when using vestibular stimulation!
VESTIBULAR PROBLEMS INVOLVING
POSTURAL CONTROL & BILATERAL
INTEGRATION
Theory:
maturation of the central vestibular system is delayed or underactive
thought to be a brainstem-based inefficiency
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CLASSIC SIGNS:
VESTIBULAR PROBLEMS INVOLVING
POSTURAL CONTROL & BILATERAL
INTEGRATION
Poor prone extension
Hypotonicity, especially proximal extensors
Poor proximal stability
Poor equilibrium reflected in low SWB score
May crave intense vestibular stimulation
Some may be posturally insecure
May have depressed duration of PRN
INDICATORS OF POOR BILATERAL
INTEGRATION
Low scores on tests of bilateral coordination
May avoid crossing midline
Two sides of body not well synchronized
• Jump with two feet together
• Skipping
• Jumping Jacks
SPECULATION:
HEMISPHERIC SPECIALIZATION
SOMETIMES MAY BE AFFECTED:
Language delays
Visual perceptual problems
Delays in establishing hand preference
HOME AND SCHOOL BEHAVIOR
CHILDREN WITH VESTIBULAR-
POSTURAL PROBLEMS
Affected by social context
Clumsiness associated with poor balance
Poor posture
May seem weak
Classically appears normal with average or higher IQ
INTERVENTION GUIDELINES:
VESTIBULAR-POSTURAL-BILATERAL
PROBLEMS
If child seeks intense vestibular input, allow it
Always monitor for safety & autonomic responses
Simple postural-ocular responses initially
Increase challenges to dynamic balance & bilateral
coordination, including bilateral projected action sequences
INTERVENTION GUIDELINES:
ACCOMMODATIONS WITH DYNAMIC
SEATING
Improved attention in class
for with children with ADHD
(Fedewa & Erwin, 2011; Schilling et al.,
2003)
Some children with autism may also
benefit
• Evaluate individually• In one study, children with autism with
poor postural stability were less engaged when sitting on ball chair (Bagatell et al., 2010)
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VESTIBULAR
MODULATION PROBLEMS
Gravitational Insecurity
Over-responsive and distressed in response to vestibular sensations, especially vertical linear
Intolerance to Movement
Easily nauseated by vestibular stimuli; not usually treated by OT when seen by itself
VESTIBULAR
MODULATION PROBLEMS
GRAVITATIONAL
INSECURITY
Classic signs:
Fear of everyday movement experiences
Changes in vertical space are difficult
Avoidance of new head positions
Anxiety when feet are away from the floor
Extremely cautious and restricted movement
Emotional and behavior problems common
GRAVITATIONAL
INSECURITY
Theory: poor vestibular modulation of otolithic input
Commonly viewed as vestibular over-responsivity
Alternative theory: proprioceptive problem –
not adequately modulating vestibular input
ASSESSMENT OF GRAVITATIONAL
INSECURITY
Parent & child interviews & questionnaires
• Sensory Profile, SPM
Clinical observations:
-- supine over bolster
-- step backwards off step-stool
-- May-Benson & Koomar (2007)
GUIDELINES:
GRAVITATIONAL
INSECURITY
Start with activities child can tolerate
Usually will start close to the ground
Stay physically close to child, giving physical supports as needed, and gradually move away
Very gradually increase challenges for movement through space
INTEVENTION
STRATEGIES FOR
GRAVITATIONAL
INSECURITY
Use child’s interests to motivate
Fantasy play very effective for introducing challenges
Social play may motivate child to overcome fears
Work on specific gross motor activity skills if child is strongly motivated to achieve them
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INTERVENTION FOR
GRAVITATIONAL INSECURITY
Goal: child who enjoys participating in physical
activities with others
Can have profound
positive effect on child’s
and family’s life
EXPANDING INTERVENTION
BEYOND THERAPY SESSIONS
Help family incorporate vestibular activities into child and family daily routines
Community-based programs: swimming, gymnastics, horseback riding, karate