Introduction to the Vestibular System - BSHAA Events/Sta… · an episode of vestibular neuronitis / labyrinthitis, or after removal of a vestibular schwannoma, i.e. any situation

Introduction to the Vestibular System Phil Gomersall With thanks to Sarah Creeke (Addenbrooke’s Hospital)

Outline

•  Vestibular system -peripheral -central

•  Vestibular-ocular reflex •  Pathologies •  Referral pathways •  Testing •  Fixing •  Summary

Structure of the Vestibular End Organs

Five 'Sensory Units' in each ear

3x Semi-circular Canals -code for rotation

2x Otoliths -code for vertical and horizontal linear acceleration

The role of the vestibular system http://www.youtube.com/watch?v=nLwML2PagbY

http://www.youtube.com/watch?v=nLwML2PagbY

http://www.youtube.com/watch?v=fsD3RDUqgJU



3x Semi-circular Canals -Membranous tubes -cross sectional diameter of 0.4mm -Filled with endolymph -2/3 of a full circle, diameter 6.5mm

2x Otoliths -code for vertical and horizontal linear acceleration

Hain, TC. http://www.dizziness-and-hearing.com. 4 April 2010 http://www.dizziness-and-balance.com/disorders/bppv/otoliths.html


3x Semi-circular Canals -Aligned (almost) orthogonally

http://bestpractice.bmj.com/best-practice/monograph/73/basics/pathophysiology.html


Sensory structure in the semi-circular canal: Crista Ampullaris:



3x Semi-circular Canals -Membranous tubes -cross sectional diameter of 0.4mm -Filled with endolymph -2/3 of a full circle, diameter 6.5mm

2x Otoliths -Globular cavities -Utricle larger than saccule, occupies upper back part of vestibule. Saccule positioned inferiorly



Transduction occurs through depolarisation of hair cells


2x Otoliths -Contains a mesh of fibres embedded in a gel. -This membrane contains otoconia – calcium carbonate crystals 0.5-30 µm diameter

Central Vestibular System

Lateral

Inferior

Medial

Superior

Cervical Cerebellum Reticular

Formation Spinal Cord

Contra. Vestib Nucleus

Balance Cerebellum Eye movements Head and Neck movements Arm and leg position Nausea Control Conscious awareness

Vestibule VIIIth Nerve

Vestibular Nucleus Periphery Brainstem

Central Vestibular System

Lateral

Inferior

Medial

Superior




Balance Cerebellum Eye movements Head and Neck movements Arm and leg position Nausea Control Conscious awareness

Vestibule VIIIth Nerve

Vestibular Nucleus Periphery Brainstem

Vestibular Ocular Reflex

Vestibular System Disorders

•  Benign Paroxysmal Positional Vertigo (BPPV) •  Ménière’s Disease •  Labyrinthitis and vestibular neuronitis •  Acoustic neuroma

BPPV

•  Thought to be caused by otoconia from the utricle floating into the semicircular canals (SSCs)

•  Idiopathic (most commonly) •  Very common

•  increasing age •  more common in women •  head trauma •  with other vestibular disorders

BPPV

Hain, TC. http://www.dizziness-and-hearing.com. 22 Sep 2010 < http://www.dizziness-and-balance.com/disorders/bppv/movies/Debris-Redistribution.gif >.

BPPV

Hain, TC. http://www.dizziness-and-hearing.com. 22 Sep 2010 < http://www.dizziness-and-balance.com/disorders/bppv/movies/Debris-Redistribution.gif >.

BPPV Symptoms

•  Motion provoked vertigo •  rolling over in bed •  head up/down

•  Duration few seconds to 2 mins •  usually abates if position maintained

•  Spontaneous resolution and recurrence

Which Canal?

Canal % of patients(a) % of patients(b)

Posterior 90 76 Anterior 2 13 Horizontal 8 5 Indeterminate (posterior or anterior)

6

(a) Fiona Barker BBPV CD (b) 200 consecutive patients (Herdman, ISVR Balance course 2001)

Affected canal identified by direction of nystagmus

Posterior SSC BPPV

http://www.youtube.com/watch?v=rtS2muvjFbM

Labyrinthitis and Vestibular Neuronitis

•  Inflammation of the vestibular end organ or nerve •  often preceded by viral infection

•  Spontaneous rotatory vertigo •  usually sudden onset, severe, with nausea and

vomiting •  hours to days’ duration

•  Gradual recovery (approx 6 weeks) •  residual motion provoked vertigo

Ménière’s Disorder

•  Spontaneous episodes of rotatory vertigo •  often with nausea and vomiting •  typically a few hours’ duration

•  Preceded/accompanied by •  aural fullness •  increased low frequency sensorineural hearing loss •  (increase in) tinnitus

•  Initially, only some symptoms may present

Prevalence of Ménière’s

•  Require ‘triad’ from four possible symptoms 1. Rotary vertigo 2. Aural fullness 3. Tinnitus 4. Sensorineural hearing loss Prevalence 0.2% of US population

•  difficult to obtain reliable data •  often over-diagnosed

“Early” Meniere’s

“Late” Meniere’s

Progression of Ménière’s

•  Often periods of remission, but usually relentless destruction of hearing and vestibular function

•  Second ear may also be affected •  estimates of bilateral prevalence vary from 17%

to 50%

•  Late stage can leave severe/profound hearing loss and even bilateral vestibular hypofunction

Acoustic Neuroma or Vestibular Schwannoma

•  Non-malignant tumour of the VIIIth nerve •  may impinge on the brainstem at the

cerebellopontine (CP) angle

•  Warning signs •  progressive unilateral/asymmetric SNHL

•  poor speech discrimination •  worsening unilateral tinnitus

•  imbalance

•  Diagnosis from MRI with gadolinium contrast

Acoustic Neuroma

Hain, TC. http://www.dizziness-and-hearing.com. 22 Sep 2010 < http://www.dizziness-and-balance.com/disorders/tumors/acoustic_neuroma.htm>.

Typical audiogram

Referral pathway: vestibular problems

GP

Anti-emetics / vestibular suppressants Watch and wait Identify BPPV : May offer Epley manouvre

ENT

Anti-emetics / vestibular suppressants Watch and wait Identify BPPV : Will offer Epley manouvre (or variants) Diagnose Meniere’s (Audiogram)

Neurology

Audiovestibular physician

Vestibular assessment MRI

Vestibular Testing

Battery of Tests available, each focuses on a different aspect of balance function: -Relative influence of vestibular; vision and proprioception on balance -Use Vestibular-Ocular reflex (VOR) to probe vestibular function -Eye muscle control as a probe of brain pathways

Combined Test of Sensory Interaction in Balance (CTSIB)

-Relative influence of vestibular; vision and proprioception on balance: CTSIB

Vestibular Testing

-Use Vestibular-Ocular reflex (VOR) to probe ‘inner ear’ function -Gaze testing -Head thrust test -Head shake testing -Positional testing -Caloric testing

Vestibular Testing

-Use Vestibular-Ocular reflex (VOR) to probe vestibular function: Caloric testing

Vestibular Testing

-Use Vestibular-Ocular reflex (VOR) to probe vestibular function: Caloric testing

Vestibular Testing

http://www.youtube.com/watch?v=Vjk1f99N13M

http://www.youtube.com/watch?v=Vjk1f99N13M

Vestibular Testing

Vestibular Testing

Vestibular Testing

-Eye muscle control as a probe of brain pathways: ‘Ocular motor tests’

• Smooth pursuit pathway

• Saccade pathway

Vestibular Testing


Vestibular Testing


Outcome of Vestibular Testing

•  Results assessed by referrer •  Further investigation -MRI -CT •  Diagnosis (Differential) •  Management options

Fixing Vestibular Problems: BPPV

Treatments centre on moving the patient’s head to try and move escaped otoconia out of the semi-circular canals and back to the otolith organs;

The exact manoeuvre depends upon which canal is affected and whether the otoconia are free or attached to the cupula

http://www.dizziness-and-balance.com/disorders/bppv/bppv.html July 2010

Vestibular Rehabilitation

http://www.dizziness-and-balance.com/treatment/rehab/gaze%20stab.html

Typical Vestibular rehabilitation exercise, repeated daily

Similar exercises can be done vertically

Also practice balance exercises

Ongoing process of gradual improvement over period of weeks

Fixing Problems: Meniere’s

Medication (control fluid pressure) - Betahistine (serc) - Diuretics Chemical oblation -  Gentamicin

Surgery - Endolymphatic sac decompression - Vestibular nerve section

Fixing Problems: Vestibular Schwannoma •  Watch wait and re-scan •  Radiotherapy

•  Surgical excision

•  All of these may include vestibular rehabilitation

Referral Criteria

Thanks

Thanks for listening! Further reading: Vestibular Rehabilitation (Contemporary Perspectives in Rehabilitation) Susan J. Herdman

Publisher: F.A. Davis; 3Rev Ed edition (1 April 2007) ISBN-10: 0803613768 ISBN-13: 978-0803613768 Balance Function Assessment and Management Gary P. Jacobson (Author), Richard E. Gans (Author), Neil Shepard Publisher: Plural Publishing Inc; 1 Har/Cdr edition (1 April 2007) Language English ISBN-10: 1597561002 ISBN-13: 978-1597561006

Fixing Chronic Vestibular Problems

For non-fluctuant motion-provoked symptoms, (another common set of symptoms encountered) vestibular rehabilitation is the recommended approach. These symptoms may be commonly encountered after an episode of vestibular neuronitis / labyrinthitis, or after removal of a vestibular schwannoma, i.e. any situation where there is an asymmetry of vestibular information between the ears.

Vestibular Rehabilitation

In the case of an asymmetry in vestibular information Physiological processes will adapt for static (resting) situations However in order for dynamic adaptation i.e. VOR to adapt during movement there must be: Intact vision and depth perception Normal proprioception in the neck and limbs Intact sensation in the lower extremities ‘Healthy’ central vestibular processing Adaptation of VOR to movement requires movement!

Fixing Vestibular Problems

When problem is spontaneous and fluctuating , i.e. Meniere’s disease, severe attacks of vertigo can strike without warning. Very significant impact on quality of life. Some medications can help stop the attacks, but mixed success. Most successful approach is to turn fluctuating lesion into a non-fluctuating problem: destroy troublesome vestibule, either with: -Vestibulotoxic medication (Gentamicin) -Surgery ..and then carry out rehabilitation as outlined before.

Fixing Vestibular Problems

A few, rare, causes of dizziness can be fixed directly by surgery: Perilymph fistula: Fluid leaking out of the vestibule can be ‘plugged’ Superior Semi-circular Canal Dehiscence: A hole in one of the semi-circular canals allows transmission of fluid and/or vibrations between skull-base and inner ear. Dizziness when exposed to loud sounds. Can be surgically repaired. This disorder can be identified by another vestibular test not discussed here that uses a reflex that links the vestibule and the neck muscles (VEMP).

Summary

Balance is a complicated process. The inner ear plays a very significant role in the maintenance of balance as part of the vestibular system. Other systems also contribute alongside. Disorders of the inner ear and/or VIIIth cranial nerve can lead to dizziness and imbalance. Other disorders can also lead to dizziness and imbalance Suitably qualified audiologists may perform a number of different tests to help determine whether dizziness is being caused by the vestibular system or not, and whereabouts in the vestibular system the problem lies. In cases of inner ear causes audiologists often play a role in aiding the recovery

process.

Summary continued

Dizziness and imbalance are very common disorders (dizziness = 2nd most common reason people attend GP). Become increasingly more common the older the individual. Dealing with people with audiological problems there is an even higher likelihood that you will come across individuals with balance problems, due to strong tie-in between audio and vestibular systems (NB VIIIth cranial nerve = audiovestibular nerve). Import to ‘red flag’ suspicious dizziness to medical experts. Most causes of dizziness are benign, yet occasionally represent significant potentially life-threatening disease. Some dizziness/imbalance can be treated to improve individual’s quality of life.

Referrable conditions (BSHAA/BAA) : -Dizziness -Swaying -Floating sensation

Spare slides (‘cos 64 ain’t enough!?)

• Verdana bullets: First order • Second order

• Third order •  Fourth order

These are all set up on the slide master View: Master> slide master to change

Irritative neuronitis

Vestibular Pathway

Lateral

Inferior

Medial

Superior




Balance Cerebellum Eye movements

Arm and leg position Nausea Control Conscious awareness

Vestibular Nucleus

Head and Neck movements

Unilateral lesion

Lateral

Inferior

Medial

Superior






Vestibular Nucleus


Endolymphatic Hydrops

•  Excess endolymphatic pressure •  blocked endolymphatic

duct? •  enlarged cochlear/

vestibular aqueduct?

•  Unclear if cause or effect of Ménière’s


Endolymphatic Sac

Endolymphatic Duct

Spontaneous Physiological Recovery

Lateral

Inferior

Medial

Superior






Vestibular Nucleus


Recovery to movement

Lateral

Inferior

Medial

Superior






Vestibular Nucleus


BPPV Mechanisms (postulated)

•  Canalithiasis •  free floating debris in canals •  supported by short duration

•  Cupulolithiasis •  otoconia stuck to cupula •  mechanism for long duration BPPV?

Case Study ...

•  43 year old man •  active, outdoor professional

•  Initial symptoms •  difficulty walking in a straight line for 5 years •  slight bradykinesia in both hands, more on left •  MRI head 2 years previously reported as normal

•  Initial differential diagnoses •  Parkinson’s disease •  psychogenic

Case Study – 6 months later ...

•  Reported gradually progressive left sided hearing loss •  unable to hear on the phone •  left-sided, constant, hissing tinnitus for past year

•  Referred for audio and vestibular assessment

Case Study – Test Results ...

•  Bilateral sensorineural hearing loss, worse in the left ear at high frequencies

•  Left peripheral vestibular system lesion •  left canal paresis of 74% •  head-shaking nystagmus

•  Some central signs •  abnormal smooth pursuit

•  Couldn’t balance on a cushion eyes closed

Case Study – MRI results ...

•  Left cerebellar peduncle angle enhancing mass lesion •  21 x 16 x 11 mm in size

•  Considered surgery or radiotherapy •  Left translabyrinthine excision

•  facial nerve intact •  residual hearing lost

•  6 weeks later •  balance improving

Case Study – Outcome

•  6 weeks post-op •  good facial function •  balance improving •  back at work full-time

•  2 years post-op •  good facial function and normal taste •  occasional imbalance •  riding a bike and climbing •  tried CROS with little benefit, accepting of hearing

loss

Why you need to know about this stuff

Exams? – only very basics , i.e : “What are the vestibular symptoms associated with Meniere’s?”

Red flags: “Vertigo or other disturbance of balance which includes dizziness, swaying or

floating sensations (frequently associated with unsteadiness) that may indicate otological, neurological or medical conditions.”

Answering questions Interest

Superior Semicircular Canal Dehiscence (SSCD) •  Thinning of the SSC wall

•  creates a “third window” in the cochlea

•  Symptoms •  awareness of body noises (eyeballs, footfalls) •  “false” air-bone gap (enhanced bc) •  present acoustic reflexes •  Tullio’s phenomenon/pressure induced nystagmus •  imbalance/dizziness

•  Diagnosis from CT and VEMP (vestibular evoked myogenic potentials)

Tullio’s Phenomenon

Hain, TC. http://www.dizziness-and-hearing.com. 22 Sep 2010 < http://www.dizziness-and-balance.com/disorders/symptoms/movies/tullio.avi>.

Perilymph Fistula

•  Abnormal opening resulting in perilymph leak •  oval or round windows

•  trauma (mechanical/barotrauma) •  surgery

•  bony canals •  cholesteatoma •  fenestration

•  Rare •  Symptoms and diagnosis similar to SSCD

Central Vestibular Disorders

•  Previous conditions are all peripheral •  Central causes include

•  stroke •  migraine •  cerebellar degeneration or malformation •  tumours •  seizures

•  Symptoms vary •  Diagnosis often from MRI

Migraine Associated Vertigo

•  The third leading cause of vertigo •  Migraine defined by International Headache

Society (IHS) •  50 – 70% of migraineurs have vestibular

symptoms

Rotatory vertigo Unsteadiness

Light-headedness

Motion-provoked dizziness

Motion-sickness Positional vertigo

Diagnosing Migraine

•  Difficult! •  no diagnostic criteria for vestibular migraine

•  Diagnosis by exclusion or confirmed by positive response to treatment

•  Vertigo usually precedes headache, but can occur with headache, or be independent •  duration: seconds to hours to days

•  Can have migraine without headache

Other factors

•  Hyperventilation syndrome •  often causes light-headedness •  can produce nystagmus •  some evidence that underlying peripheral

vestibular disturbances may be heightened by hyperventilation

•  important to address breathing control before underlying disorder

•  Anxiety and depression

Documents

Introduction to the Vestibular System - BSHAA Events/Sta… · an episode of vestibular neuronitis / labyrinthitis, or after removal of a vestibular schwannoma, i.e. any situation