vestib lecture 2014.ppt · lvst matures at ~ 6 months postnally (landau) vestibulo-ocular responses...

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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


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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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


Descending Vestibulospinal Pathways:

Lateral vestibulospinal tract (LVST)

Medial vestibulospinal tract

(MVST)

Reticulospinal tract


Descending Vestibulospinal Pathways:

Lateral vestibulospinal tr.

Medial vestibulospinal tr.

Reticulospinal tract

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Functions of Descending (Spinal) Pathways:

Head righting and equilibrium reactions (transient & sustained)

Powerful autonomic effects

Proprioception modulates vestibular input


Brainstem-Level Pathways:

Reticular formation

Vestibulocerebellar

pathways


Ascending Pathways:

Vestibulo-ocular pathways

Reticular-limbic pathways

Vestibulo-cortical projections


Vestibulo-ocular pathways:

Vestibular nuclei to ocular-motor cranial nerves

Mediate compensatory eye movements for stable visual field


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


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)


More on Vestibular Nystagmus

Slow phase:

Velocity closely related to peripheral function

Fast phase:

Mediated by central mechanism in brainstem


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


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


Reticular-limbic pathways

Vestibular n. �� reticular system �� limbic system

Emotional responses to vestibular stimulation

Increased eye contact during vestibular stimulation


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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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

vestib lecture 2014.ppt · lvst matures at ~ 6 months postnally (landau) vestibulo-ocular responses...

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