Post on 18-Feb-2022
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
Structure of the Vestibular End Organs
Five 'Sensory Units' in each ear
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
Structure of the Vestibular End Organs
3x Semi-circular Canals -Aligned (almost) orthogonally
http://bestpractice.bmj.com/best-practice/monograph/73/
basics/pathophysiology.html
Structure of the Vestibular End Organs
Sensory structure in the semi-circular canal: Crista Ampullaris:
Structure of the Vestibular End Organs
Five 'Sensory Units' in each ear
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
Hain, TC. http://www.dizziness-and-hearing.com. 4 April 2010 http://www.dizziness-and-
balance.com/disorders/bppv/otoliths.html
Structure of the Vestibular End Organs
Transduction occurs through depolarisation of hair cells
Structure of the Vestibular End Organs
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
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
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
-Eye muscle control as a probe of brain pathways: ‘Ocular motor tests’
Vestibular Testing
-Eye muscle control as a probe of brain pathways: ‘Ocular motor tests’
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
Cervical
Cerebellum Reticular Formation
Spinal Cord Contra. Vestib Nucleus
Balance
Cerebellum
Eye movements
Arm and leg position
Nausea Control Conscious awareness
Vestibular Nucleus
Head and Neck movements
Unilateral lesion
Lateral
Inferior
Medial
Superior
Cervical
Cerebellum Reticular Formation
Spinal Cord Contra. Vestib Nucleus
Balance
Cerebellum
Eye movements
Arm and leg position
Nausea Control Conscious awareness
Vestibular Nucleus
Head and Neck movements
Endolymphatic Hydrops
• Excess endolymphatic pressure • blocked endolymphatic
duct?
• enlarged cochlear/vestibular aqueduct?
• Unclear if cause or effect of Ménière’s
Hain, TC. http://www.dizziness-and-hearing.com. 4 April 2010 http://www.dizziness-and-balance.com/disorders/bppv/otoliths.html
Endolymphatic Sac
Endolymphatic Duct
Spontaneous Physiological Recovery
Lateral
Inferior
Medial
Superior
Cervical
Cerebellum Reticular Formation
Spinal Cord Contra. Vestib Nucleus
Balance
Cerebellum
Eye movements
Arm and leg position
Nausea Control Conscious awareness
Vestibular Nucleus
Head and Neck movements
Recovery to movement
Lateral
Inferior
Medial
Superior
Cervical
Cerebellum Reticular Formation
Spinal Cord Contra. Vestib Nucleus
Balance
Cerebellum
Eye movements
Arm and leg position
Nausea Control Conscious awareness
Vestibular Nucleus
Head and Neck movements
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