otolith and bppv use file - university of floridaapplied vestibular anatomy 29 head moves to the...

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How the Labyrinth Works…

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Inner Ear: “On Top of a Long Stalk”

Vestibular Function SCCs:

©2012 MFMER | slide-13

• Semicircular canals• Translates angular rotation movements of

the head around the pivot point of the neck• Information used by the CNS to coordinate:

• Eye movements• Upper torso movement• Hand movements while moving

• See aVOR app in the iTunes Store

Vestibular Function Otoliths:


Micro-Structure of the Macula

Utricle Encoding: Static Tilt and Acceleration

www.utdallas.edu/~tres/integ/ sen5/sense_5.html

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Primary Goal of Otolith Organs

• Anti-gravity muscle tone • Vestibular Spinal Reflexes (VSR)

• Vestibular Ocular Reflexes :• Maintain registration of the retina with

gravitational vertical • Horizontal meridian of the retina aligns

automatically with the horizon

Macula: Linear Translations and Low Frequency Tilts

• Sensitive to movements about the...

•Hips•Ankles

• Play an important role in maintaining upright stance

Ocular Tilt Reaction

Modified from: Brandt & Dietrich, 2000, in S.J. Herdman, Vestibular Rehabilitation

Vestibulo-Macular Ocular Reflex

Goal: Keep eyes aligned with gravitational vertical

Common Otolith Disorders

• BPPV• Most common cause of vertigo in adults

• Superior vestibular nerve “neuro-laybrinthitis”• Second most common cause of dizziness

• Clinically:• “Neuronitis”

• Vestibular symptoms only• “Labyrinthitis”

• Auditory and vestibular symptoms

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Major Nerves In The Internal Auditory Canal (IAC)

FN

CN

SVN

IVN

Facial N. - Superior & AnteriorCochlear N. - Inferior & AnteriorSuperior Vestibular N.Inferior Vestibular N.

A P

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Vestibular Tests and Eighth Nerve BranchesWe can now measure all sensory structures and nerve branches of the inner ear

• Audiological Evaluation

• Caloric response

• oVEMP

• cVEMP• vHIT

• Cochlea• Horizontal SCC (SVN)

• Utricle (SVN)• Saccule (IVN)• All SCCs (SVN/IVN)


Vestibular Study

• Normal• Ocular motor• (-) positional

nystagmus -50 -40 -30 -20 -10 0 10 20 30 40 50

Warm

Cold

Caloric Responses 80% LEFT WEAKNESS

Left Right


Absent cVEMP on LEFT Absent oVEMP on LEFT

Summary Points Three SSC

Encode angular rotation about cervical spine◦ Two otolith organs

Encode linear translations and drive strong neck and spine muscle reflexes.

Vestibular Nerve: LSU on top!

Vestibular nuclei (VN) and cerebellum involved with VOR / VSR / autonomic tone

Applied Vestibular Anatomy

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Ways to Understand the Vestibulo-Ocular Reflex


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Right Semi-Circular Canal Cup • Cup is in the place of the right

SSC•Handle is in the position of the ampulla•Cap represents endolymphposition before any head movement

• Note position of the utricle (medial)


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Head Moves to the left... Ampulla moves with the

head (to the left)◦Cap does not move, but changes position relative to the ampulla due to head movement (curved arrow)

It “lags behind” the head movement

Endolymph moves through the ampulla, away from the utricle


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Head Moves to the Right• Ampulla moves with the head

(to the right)•Cap does not move, but changes position relative to the ampulla due to head movement

• Endolymph moves through the ampulla, toward from the utricle


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Head Moves to the Right

The long arrow (endolymph) does not change its orientation…neither do the eyes.

Vestibular eye movements lawfully reflect relative movement of endolymph in the SCCs


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Vestibulo-Ocular Reflex (VOR)

Shepard and Telian 1995Applied Vestibular Anatomy

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Semicircular Canal aVOR

• Goal:• Maintain visual stability (visual image on

retina) despite “angular” head movements about cervical spine


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Semicircular Canal aVOR

• Three orthogonal SSCs reflect movements in three dimensions

• Three SCCs pairs (left and right) are coplanar

• When one SCC is stimulated, its coplanar complement is inhabited


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A word about nerve firing rates...


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Firing Rate Example (Hypothetical)

100 100

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Left Ear Right Ear

• When the head is still, both nerves fire at about 100 spikes/sec.

Applied Vestibular Anatomy 36


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Left Ear Right Ear

• Head turns to the right at a velocity of 40 degrees / sec,

• Discharge rate increases in the right (leading) ear

• Discharge rate decreases in the left (lagging) ear



5

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Left Ear Right Ear

• The brain interprets this asymmetry in nerve output between ears as a head movement to the right at 40 deg/sec.

• The brain moves the eyes to the left at 40 deg/sec

• vestibular slow phase movement of nystagmus



0

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Left Ear Right Ear

• When the head turns to the right at 100 deg/sec.

• The right nerve firing rate jumps up

• The left ear cannot change

• You can’t fire less than zero times / sec ;-)



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Left Ear Right Ear

• Any angular head movement that exceeds a critical velocity is encoded entirely by the leading ear.

• The “lagging ear” contributes little to the VOR at high velocities of rotation


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How Is This Helpful?…. Head Thrust Test

(+)

(-)

Jacobson et.al.,Applied Vestibular Anatomy

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Ecological Approach to Vestibular Evoked Eye Movements

• Vestibular evoked eye movements are designed to:

• Maintain gaze stability during unexpected head / body movements

• Maintain eye orientation so that the horizon lines up with the horizontal meridian of the retina

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A Model...

Right Left


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PHA

PHARight Left


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SSC Planes

Six SSCs are matched in complement pairs -three planes…◦ Two Horizontal◦ Right Anterior and Left

Posterior

(RALP)◦ Left Anterior and Right

Posterior

(LARP)

RALPLARP

Right Left


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Law of Reciprocal Innervation

• Head movements that stimulate the nerve of one canal, inhibit output in the complementary canal

• Leading Ear Excites• Lagging Ear Inhibits

RALPLARP

Right Left


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Horizontal Canal Dynamics

• Q: Which way does the cupulla of the horizontal canal bend to excite the vestibular nerve?

• A: It “swings away from” the leading ear.• Ampullopetal flow - endolymph flows towards

the utricle


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Horizontal Canal Dynamics


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Relating Horizontal SSC Output to VOR

So with Left Head Turn:◦ The Left Horizontal SCC

Excites Left Vestibular Nerve ◦ Right Horizontal SCC

Inhibits Right Vestibular Nerve

The Eyes Drift to the Right side of the Orbit to maintain Gaze stability (VOR)

Right Left


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Right Left

• So with Left Head Turn:• The Left Horizontal

SCC Excites Left Vestibular Nerve

• Right Horizontal SCCInhibits Right Vestibular Nerve

• The Eyes Drift to the Right side of the Orbit to maintain Gaze stability (VOR)


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Right Left


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Right Left


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At some point, gaze stability cannot be maintained and a saccade moves the eyes to a new fixation target…◦ Nystagmus “Fast

phase”◦ Not Vestibular Induced

Right Left


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Understanding Vertical SSCs

• “Goals” of VOR• Maintain Gaze stability

despite head movement• Maintain eyes oriented to

the horizon• Gravitational

Horizontal should line up with horizontal meridian of retina

RALPLARP

Right Left


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• What Kind of Eye Movement Is Necessary When Moving in the “Right - Anterior , Left Posterior” (RALP) Plane?


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RALP Movement

• Turn Head 45o to Left

• RALP Movement:• Tilt Forehead Down• Look Straight

Ahead• What Do Eyes Do?

Right Left


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RALP Movement




Right Left


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RALP Movement




Right Left


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RALP Movement

• Right Eye elevates

• Slight Counter Clockwise Torsional eye movement (relative to the patient)Right Left


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RALP Movement

• At some point, gaze stability cannot be maintained and a saccade moves the eyes to a new fixation target…

•Nystagmus “Fast phase”•Not Vestibular Induced

Right Left


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RALP Movement This is the Effect of Right

Anterior Canal Stimulation (When looking to the right):◦ Right Eye elevates◦ Slight Counter-clockwise

Torsional “Slow phase” eye movement (relative to the patient)Right Left


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RALP Movement

When looking to the left of Right Anterior Canal Stimulation provokes:◦ Minimal vertical

movement◦ Counter-clockwise

Torsional “Slow phase” eye movement (relative to the patient)

Right Left


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RALP Eye Movements

• Vertical component changes with direction of gaze

• Eye movement remains “in the plane of” the dependent canals (Arrow)

RALPLARP

Right Left


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RALP Plane Movements

Looking LeftLooking Right

- Plane of rotation is the same regardless of gaze direction- Trajectory of the pupil depends on direction of gaze


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Vertical Canal Cupula

• How does the cupula of the leading vertical canal move when the head tilts in the RALP plane?


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Vertical Canal Dynamics

• It “falls” toward the head tilt.• Ampullofugal Flow or Flow away from the

utricle.

Parnes et.al, 2003


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Summary Point: #1

• Vestibular Induced Eye Movements:• Maintain gaze stability during unexpected

head / body movements• Maintain eye orientation so that the horizon

lines up with the horizontal meridian of the retina


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Summary Point: #2

• In Angular Head Movements• The leading canal excites the vestibular

nerve • Lagging canal suppresses vestibular nerve

firing• Provokes a slow eye movement in the

opposite direction of the head movement (Ewald).

• The leading canal will drive eye movements in response to fast accelerations (Ewald).


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Summary Point: #3

• For horizontal or “yaw” type of excitatory movements, the cupula lags behind the leading ear

• For vertical movements (RALP or LARP planes), the cupula falls in the direction of the head movement


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BPPV Induced Eye Movements


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Benign Paroxysmal Positional Vertigo (BPPV)

• Intense but transient vertigo provoked by moving into specific head positions

• Most common cause of vertigo• Accompanied by a characteristic nystagmus• Thought to be caused by debris in the

semicircular canals• Can be treated by a simple in office

procedure

71Applied Vestibular Anatomy

Understanding BPPV Induced Eye Movements

• Simple forms are easy to recognize:• Posterior SSC BPPV is torsional, with the

top pole of the eye rolling to the floor.• For more complicated types of nystagmus:

• Relate the eye movement to the type of head movement that would normally drive the eyes in that direction.

• “Analogous Equivalent Movement”



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Dix-Hallpike or Nylen Maneuver

Furman and Cass “Benign Paroxysmal Positional Vertigo.” NJM 1999.

Characteristic Response

• Torsional nystagmus (rolling eye movement) & vertiginous sensation

• Onset latency (5-45 sec)• Crescendo then fatigues

(typically within 30 sec)• Symptoms extinguish (adapt)

over repeated trials


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Analogous Equivalent Head Movement

• Analogous equivalent head movement• Visualize which semicircular canals would be

stimulated or inhibited during such a movement

• This will tell you where the debris rests in the labyrinth.


Posterior Canal BPPV

• Eye movement:•Top of eye rolls to the floor

•Counter clockwise (relative to the patient)

•Up beating component, >in the contralateral eye

• Eye movement is analogous to falling in the plane of the involved posterior canal


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Analogous Head Movement

• Nystagmus is torsional and vertical, with upper pole of eye beating to the floor (fast phase)

• Nystagmus is the same as if the head was going back for a Dix-Hallpike Maneuver

• Cupula leans into the movement (excitatory)


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•Nystagmus is the same as if the head was going back for a Dix-Hallpike Maneuver•Cupula leans into the movement (excitatory)


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Right Posterior Canal BPPV


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Head in the Dependent Position

• Same up and clockwise (relative to the patient) torsional nystagmus as when moving into the Dix-Hallpike position from sitting.

• Onset delay• Upward component

greatest with gaze to the left


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Debris Falls From the Pull of Gravity

Cupula bends Same Up and Clockwise

(relative to the patient) Torsional Nystagmus as when moving into the Dix-Hallpike Position From Sitting.◦Onset delay◦Upward component greatest with gaze to the left


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Posterior Canal Variety

• Eye movement is analogous to falling in the plane of the involved posterior canal

•Top of eye rolls to the floor

•Counter clockwise (relative to the patient)

•Up beating component, >in the contralateral eye


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Dizzy!

Dizzy! Could be Dizzy!

Epley ManeuverRight Posterior Canal


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Superior Canal Variations

Modified from: Furman & Cass Benign Paroxysmal Positional Vertigo. NJM, 341:21 1999


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Contralateral SC-BPPV Quick Rules of Thumb

• For vertical / torsional nystagmus…

• Up-beating eye implies the contralateral posterior canal

• Down-beating eye implies the ipsilateral anterior canal


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Back to our Case

• Why the Down Beating Nystagmus on Dix –Hallpike?


Back to our Case

• Right Anterior Canal BPPV


Detecting Anterior Canal BPPV

Side Lying Maneuver with the Nose Down

AC-BPPV

• Try a reverse Epley Maneuver• Example is for left anterior canal...


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Epley Omniax® System


Down Beating Positional Nystagmus

• Central:• Enhances with hyperventilation • Enhances with lateral eye position• Seldom with torsional Component• Rare

• Anterior Canal• Torsional component variably present with

eye position• More common


Canalithiasis Treatments (Bed Side):

• Posterior Canal

• Horizontal Canal

• Anterior Canal

• Epley

• Barrel roll

• Reversed Epley

• Deep Head tilt

From: Baloh, R. W. (1998) “Dizzy Patients: The Varieties of Vertigo”in: Hospital Practice, http://www.hosppract.com/issues/1998/06/dmmbal.htm

Epley Omniax® System


Treatment Outcome

• Down beating nystagmus diminished with EpleyChair Treatment.

• Patient not so unsteady when first getting up in the morning.

• Still unsteady on feet


Fig. 9 Simplified schematic diagram of some of the possible pathways underlying the cVEMP and oVEMP responses and the patternof the asymmetry of n10 and p13 after complete and partial unilateral vestibular loss. It is consistent with the evidence from <ce...

Ian S. Curthoys

A critical review of the neurophysiological evidence underlying clinical vestibular testing using sound, vibration and galvanic stimuli

Clinical Neurophysiology, Volume 121, Issue 2, 2010, 132 - 144

http://dx.doi.org/10.1016/j.clinph.2009.09.027

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VEMP Response Absence by Age

cVEMP

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oVEMP

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oVEMP and BPPV Age of Onset

oVEMP BPPV

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MALE FEMALE

otolith and bppv use file - university of floridaapplied vestibular anatomy 29 head moves to the...

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