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Vestibular Examination ANATOMY & FUNCTION Carmen Casanova Abbott PT, PhD.

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Presentation on theme: "Vestibular Examination ANATOMY & FUNCTION Carmen Casanova Abbott PT, PhD."— Presentation transcript:

1 Vestibular Examination ANATOMY & FUNCTION Carmen Casanova Abbott PT, PhD

2 Lecture Objectives ► Discuss vestibular structure as it relates to vestibular function when examining a dizzy patient. ► Discuss signs and symptoms associated with vestibular disorders ► Differentiate between peripheral and central vestibular pathology ► Discuss components of a physical therapy vestibular examination.

3 Vestibular System Function ► Provides information concerning gravity, rotation and acceleration ► Serves as a reference for the somatosensory & visual systems ► Contributes to integration of arousal, conscious awareness of the body via connections with vestibular cortex, thalamus and reticular formation ► Allows for:  gaze & postural stability  sense of orientation  detection of linear & angular acceleration

4 Vestibular Anatomy ► Peripheral sensory apparatus  detects & relays information about head angular & linear velocity to central processing system  orients the head with respect to gravity ► Central processing system  processes information in conjunction with other sensory inputs for position and movement of head in space ► Motor output system  generates compensatory eye movements and compensatory body movements during head & postural adjustments

5 Peripheral Apparatus ► Membranous Labyrinth  Semicircular canals (SSC)  Otolith organs

6 Netter ‘97

7 Semicircular Canals ► Angular acceleration ► Ampulla contains sensory epithelium

8 SSC Coplanar Pairing ► Spatial arrangement of the 6 SSC cause 3 coplanar pairings  R & L lateral, L anterior and R posterior; l posterior & R anterior; R & L horizontal ► Allows for a Push-Pull arrangement of the two sides (e.g., as head turns right, right SSC will increase firing rate & the left SSC will decrease firing rate) ► Advantages  sensory redundancy  common mode rejection/noise  assist in compensation for sensor overload

9 Inhibitory Cutoff ► Depolarization of the ipsilateral hair cells occurs during angular head movements ► Hyperpolarization of contralateral hair cells occurs at the same time ► Hair cells are only able to hyperpolarize to what they were at rest = cut off of inhibitory influences from the movement going in the opposite direction even if the ipsilateral hair cells continue to spike higher firing rates

10 Purves 2001

11 Otoliths ► Utricle and saccule ► Otolith sensory structures  Maculae  Otolithic membrane  Otoconia ► Movement of gel membrane & otoconia cause a shearing action to occur over the hair cells → sensitivity of otoliths

12 Otolith Function ► Respond to:  Linear head motion on acceleration  Static tilt  Two organs respond to respective accelerations or tilts in their respective planes ► Saccule has vertical orientation of maculae ► Utricle has horizontal orientation of maculae

13 Bear 1996

14 Purves 2001.

15 Hair Cells ► 2 types: kinocilium & stereocilia ► Sensory structures for the peripheral end organs (maculae and ampula) ► Hyperpolarized or depolarized depending upon the direction of deflection of the stereocilia (movement of stereocilia towards the kinocilium causes depolarization of the hair cell) ► Affect the firing rate of the primary vestibular afferents to the brainstem

16 Bear 1996

17 Striola of the Macula ► Striola serves as a structural landmark ► Contains otoconia arranged in narrow trenches, dividing each otolith ► Orientation of the hair cells change over the course of the macula ► Allows otoliths to have multidirectional sensitivity

18 Purves 2001.

19 Principles of the Vestibular System ► Tonic firing rate ► Vestibular Ocular Reflex ► Push-pull mechanism ► Inhibitory cutoff ► Velocity storage system

20 Ascending Pathways ► Vestibular nerve ► Vestibular nuclei ► Cerebellum ► Oculomotor complex  CN 3, 4, and 6  Along with vestibulospinal reflexes coordinate head and eye movements

21 Relay Centers ► Thalamus  Connection with vestibular cortex and reticular formation → arousal and conscious awareness of body; discrimination between self movement vs. that of the environment ► Vestibular Cortex  Junction of parietal and insular lobe  Target for afferents along with the cerebellum ► Both process vestibular information with somatosensory and visual input

22 Netter 1997

23 Tonic Firing Rate ► Vestibular nerve and vestibular nuclei have a normal resting firing rate ( cycles/sec) ► Baseline firing rate present without head movement ► Tonic firing is equal in both sides; if not, a sense of motion is felt e.g., vertigo, tilt, impulsion, spinning ► Excitation and inhibition of the vestibular system can then occur from stimulation of the hair cells ► Spontaneous recovery with light

24 Vestibular-Ocular Reflex (VOR) ► Causes eyes to move in the opposite direction to head movement ► Speed of the eye movement equals that of the head movement ► Allows objects to remain in focus during head movements

25 Compensatory Eye Movements ► VOR ► Optokinetic reflex ► Smooth pursuit reflex, saccades, vergence ► Neck reflexes  combine to stabilize object on the same area of the retina=visual stability

26 Purves 2001.

27 Vestibular Processing Gain ► Keeps eye still in space while head is moving ► Ratio of eye movement to head movement (equals 1)

28 Vestibular Processing Velocity Storage Mechanism ► Perseveration of neural firing in the vestibular nerve by the brainstem after stimulation of SSC to increase time constant (10sec.)  SSC respond by producing an exponentially decaying change in neural firing to sustained head movement ► Otolith & somatosensory input also drive mechanism

29 VOR Dysfunction ► Direction of gaze will shift with the head movement ► Cause degradation of the visual image ► In severe cases, visual world will move with each head movement

30 Oscillopsia ► Visual illusion of oscillating movement of stationary objects ► Can arise with lesions of peripheral or central vestibular systems ► Indicative of diminished VOR gain  motion of images on fovea  diminished visual acuity

31 Cerebellum ► Monitors vestibular performance ► Readjusts central vestibular processing of static & dynamic postural activity ► Modulates VOR ► Provides inhibitory drive of VOR (allows for VOR c )

32 Descending Pathways ► Provide motor output from the vestibular system to:  Extraocular muscles (part of VOR)  Spinal cord & skeletal muscles (generate antigravity postural activity to cervical, trunk & lower extremity muscles) ► Response to changing head position with respect to gravity (righting, equilibrium responses)

33 Vestibulospinal Reflex (VSR) ► Generates compensatory body movement to maintain head and postural stability, thereby preventing falls

34 Netter 1997

35 Vestibular Dysfunction

36 Demographics ► Vestibular disorders manifested by vertigo are a significant health problem, secondary only to low back pain ► NIH study estimates that 40% of the population over the age of 40 will experience a dizziness disorder during their lifetime

37 Fall Demographics ► Falls will be experienced in community dwelling individuals:  % over age 65  42-49% over age 75 ► Greater than 60% will have bilateral vestibular lesion (BVL) in the 75 years of age

38 Fall Risk Factors ≥ 4 risk factors, 78% chance of falling in an older adult ► Sedatives ► Cognitive impairment ► Palmomental reflex ► LE disability ► Foot problems ► Balance abnormalities ► Dizziness ► ↑ dependence on visual cues ► Fear of falling ► Orthostatic hypotension (Tideiksaar R 1998)

39 Other Fall Risk Factors?

40 Aging Changes ► Progressive changes begin at age 40  Decreased number of hair cells  Decreased vestibular nerve fibers ► Lead to dizziness and vertigo ► Harder to deal with competing visual and somatosensory input

41 Fear of Falling (FOF) ► FOF affects willingness to participate in physical activity & exercise ► FOF occurs in an average of 30% of older adults who have not fallen ► FOF increases to an average of 60% of older adults who have fallen ► FOF is higher among women ► Prevalence of FOF is underestimated ► Greater FOF associated with lower quality of life in mental health, social & leisure pursuits (Legters, 2002)

42 Falls Related Self-efficacy ► Falls Efficacy Scales (FES)  better for frail  indoor activities ► Activities-Specific Balance Confidence Scale (ABC)  higher functioning  indoor & outdoor activities  > discrimination between fearful & nonfearful (Legters, 2002) (Legters, 2002)

43 Vestibular Pathophysiology ► Disorders of tone & or gain (vertigo / movement- induced vertigo) ► Vestibular nerve / nuclei give abnormal sensory information ► Tone automatically recovers in a few days; does not need visual input ► Compensation for reduced gain depends on visual images; takes month to years to complete; high speeds & accelerations may never be complete ► Nystagmus usually transient sign of vestibular lesion; movement-induced symptoms can be chronic

44 Dizzy Patient Presentation: unexplained or new onset of symptoms ► Medical referral is indicated  constant vertigo  lateralpulsion  facial asymmetry  speech & or swallowing difficulties  oculomotor dysfunction  vertical nystagmus  severe headaches  recurrent falls  unilateral hearing loss, tinnitus, fullness, ear pain

45 Vertigo ► An asymmetrical firing of the two vestibular systems ► Gives an illusion of spinning, movement ► Indicative of any one or combination of causes (acute UVH, BPPV, brainstem lesion, vascular hypotension…)

46 Differentiation Between Peripheral & Central Causes of Vertigo Peripheral Central Peripheral Central Nauseasevere moderate Imbalancemild severe Hearing Losscommon rare Oscillopsiamild severe Neurologic Symptomsrare common Compensationrapid slow ( Furman JM, Whitney SL. 2000)

47 Peripheral Vestibular Disorders ► Vestibular Neuronitis ► Labyrinthitis ► Meniere’s ► Acoustic Neuroma ► Fistula ► Benign Paroxysmal Positional Vertigo (BPPV)

48 Central Vestibular Disorders ► Vascular  Wallenberg’s Syndrome  Head Injury  Cerebellar Infarct ► Postconcussive Syndrome ► Demyelinating Disease ► Congenital

49 Degenerative Cerebellar Disease ► Signs & symptoms  abnormal ocular pursuit  gradual decline  irregular saccades  gaze end point nystagmus  ataxia

50 Objective of Clinical Exam ► Establish location & severity of lesion (central or peripheral) ► Typical examination - history (hearing status) - cranial nerves - vestibular spontaneous nystagmus (imbalance in tone) postural instability (abnormal tone & gain; proprioceptive loss) VOR gain (maintained fixation, dynamic visual acuity) head shaking (compensated UVL; not necessarily PVL) calorics pressure sensitivity (fistula) positional nystagmus (Hallpike-Dix test) hyperventilation (anxiety; acoustic neuroma)

51 Nystagmus ► Rapid alternating movement of eyes in response to continued rotation of the body ► Primary diagnostic indicator in identifying vestibular lesions ► Physiologic nystagmus  vestibular, visual, extreme lateral gaze ► Pathologic nystagmus  spontaneous, positional, gaze evoked ► Labeled by the direction of the fast component ► Central vs. peripheral cause differentiated by duration

52 Vestibular Function Tests ► Caloric test ► Rotary Chair test ► Posturography

53 Results of Vestibular Function Tests ► Presence of complete vs. incomplete loss ► Presence of peripheral vs. central dysfunction ► Direct patient management ► Help in outcome prediction

54 Dizziness Handicap Inventory ► Three subscales  function  emotion  physical aspects ► Scoring  Yes4 pts.  Sometimes 2 pts.  No 0 pts. ► Excellent test-retest reliability

55 Hallpike-Dix Maneuver ► Gold standard used to check for the presence of benign paroxysmal positional vertigo (BPPV) ► Nystagmus induced by this test is an objective measurement from which we can determine SSC dysfunction and assess a response to treatment

56 Benign Paroxysmal Positional Vertigo (BPPV) ► Signs & symptoms  sudden, severe attacks of vertigo precipitated by certain head positions & movements ► e.g., rolling over, neck extension, bending forward  lightheadedness; nausea  anxiety  avoids movement  direction & duration of nystagmus differentiates between BPPV & a central vestibular lesion (CVL)

57 Benign Paroxysmal Positional Vertigo (BPPV) ► 5 criteria crucial in diagnosis (Hallpike-Dix Test):  torsional/linear-rotary nystagmus; reproduced by provocative positioning with affected ear down  nystagmus of 1-5 sec. latency  nystagmus of brief duration (5-30 sec.)  reversal of nystagmus direction on returning to upright position  response diminishes with repetition of maneuver (fatigability) ( Massoud ’96)

58 BPPV Cupulolithiasis ► Debris, probably fragments of otoconia from the utricle, adhere to the cupula ► Treatment  Brandt-Daroff habituation exercises  Semont, liberatory maneuver

59 BPPV Canalithiasis ► Debris floating freely in the endolymph in the long arm of the posterior SSC ► Treatment  Canalith repositioning maneuver (Epley)  84-90% remission rate  Sleep upright one night only (more severe cases)

60 Problems Experienced with Vestibular Loss ► Balance & gait deficits ► Head movement-induced dizziness ► Head movement-induced visual blurring (oscillopsia) ► LE dressing difficulty ► Driving deficits ► Disability related to work, social & leisure activities

61 Systems Approach to Examination ► Examination of balance & mobility using a variety of tests & measurements to document functional abilities, determine underlying sensory, motor, & cognitive impairments contributing to functional disabilities

62 Balance ► Can be viewed as a motor skill that emerges from the interaction of multiple systems ► These systems are organized to meet functional task goals & are constrained by the type of environment ► Balance, like any skill, can improve with practice

63 Balance Components ► Steadiness ► Symmetry ► Dynamic stability

64 Balance Training: Postural Biofeedback ► Postural symmetry & dynamic stability have been consistently improved by training using force platform systems

65 Clinical Test of Sensory Interaction In Balance (CTSIB) ► Assesses pattern of sensory dependence for balance from timed stance tests during distortion of sensory environment

66 Berg Balance Scale ► Performance -orientated balance assessment ► Interpretation:  > 45/56 score highly specific (96%) for nonfallers  subjects who fell most frequently were those closer to cut off ► Correlates with other balance tests

67 Functional Gait Assessment (FGA) ► Assesses postural stability during walking ► Modified version of the Dynamic Gait Index ► Added 3 new tasks to increase challenge and sensitivity of the test to minor changes in gait ► Stronger vestibular components (head turns, narrow BOS, ambulating backwards and with eyes closed)

68 General Therapeutic Intervention Objectives ► Changing impairments ► Improving functional performance ► Improving capacity to adapt performance to changing task & environmental demands

69 Mechanism of Recovery: Compensation ► Results from changes in CNS  rebalancing of tonic activity within vestibular nuclei (spontaneous recovery)  recovery of VOR (vestibular adaptation)  habituation (progressive decline in response to same stimulus)  alternative strategies/substitution; in complete loss of vestibular function ► Enhanced by active movements & processing of visual, vestibular, & somatosensory stimuli

70 Result of Early Intervention ► Gain returns quicker ► Increased function ► Decreased gait ataxia ► Decreased perception of disequilibrium (Herdman 2000)

71 Vestibular Exercise Program Objectives Vestibular Exercise Program Objectives ► Complement CNS natural compensation  diminish dizziness & vertigo  enhance gaze stabilization  enhance postural stability in static & dynamic situations ► Increase overall functional activities ► Patient education  nature of pathology  episodic nature, prognosis  control of exacerbations

72 Vestibular Program Components ► Gaze stabilization exercises to retrain VOR function ► Balance retraining to retrain VSR function ► Conditioning exercises to increase fitness level ► Habituation or canal repositioning maneuvers as indicated

73 e.g., Unilateral Vestibular Lesion: Exercise Guidelines ► Adaptation is best stimulated by producing an error signal; work at limit of abilities ► Incorporation of head movements & visual input ► Provide context specific stimulation to promote adaptation ► Adaptation is positively affected by voluntary muscle control ► (Herdman 2000)

74 Vestibular Function Recovery Rates ► UVL: 6-8 weeks ► BPPV: remission in 1/few treatments ► BVL: 6 months - 2 years ► CNS Lesion: 6 months - 2 years

75 Physical Therapy Intervention: Prescription ► Individualized vestibular rehabilitation program:  Outpatient, 1-2 times / week (4-6 weeks)  HEP, 5 minutes, 3x / day  Walking program (health & fitness prescription) ► Compliance to daily program essential to success ► Exercise graduated for possible increase of symptoms during the first week


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