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Introduction to the Vestibular System

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Introduction to the Vestibular System 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 2x Otoliths -code for rotation -code for vertical and horizontal linear acceleration http://www.youtube.com/watch?v=nLwML2PagbY The role of the vestibular system 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 2x Otoliths -Membranous tubes -code for vertical and -cross sectional horizontal linear diameter of 0.4mm acceleration -Filled with endolymph -2/3 of a full circle, diameter 6.5mm 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 2x Otoliths -Membranous tubes -Globular cavities -cross sectional -Utricle larger than diameter of 0.4mm saccule, occupies -Filled with endolymph upper back part of -2/3 of a full circle, vestibule. Saccule diameter 6.5mm 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 Periphery Brainstem Balance Vestibule VIIIth Vestibular Nucleus Cerebellum Nerve Superior Eye movements Head and Neck movements Lateral Medial Arm and leg position Inferior Nausea Control Conscious awareness Cervical Cerebellum Contra. Vestib Nucleus Reticular Spinal Cord Formation Central Vestibular System Periphery Brainstem Balance Vestibule VIIIth Vestibular Nucleus Cerebellum Nerve Superior Eye movements Head and Neck movements Lateral Medial Arm and leg position Inferior Nausea Control Conscious awareness Cervical Cerebellum Contra. Vestib Nucleus Reticular Spinal Cord Formation 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 6 (posterior or anterior) (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 Typical audiogram Hain, TC. http://www.dizziness-and-hearing.com. 22 Sep 2010 < http://www.dizziness-and-balance.com/disorders/tumors/ acoustic_neuroma.htm>. Referral pathway: vestibular problems GP ENT Audiovestibular physician Neurology Anti-emetics / Anti-emetics / vestibular suppressants vestibular Watch and wait suppressants Identify BPPV : Will offer Epley Watch and wait manouvre (or variants) Identify BPPV : May Diagnose Meniere’s (Audiogram) offer Epley manouvre 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=Vjk1f99N13Mhttp://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 Typical Vestibular rehabilitation exercise, repeated daily Similar exercises can be done vertically Also practice balance exercises http://www.dizziness-and-balance.com/treatment/rehab/gaze%20stab.html 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’
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