Vestibular Function and Anatomy

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					Vestibular Function and
       Anatomy

     Prof. Hamad Al-Muhaimeed
        Professor/Consultant

    Department of Otorhinolaryngology
    King Abdulaziz University Hospital
 System of balance
 Membranous and bony labyrinth embedded in
  petrous bone
 5 distinct end organs
   – 3 semicircular canals: superior, lateral,
     posterior
   – 2 otolith organs: utricle and saccule
 Semicircular canals sense angular acceleration
 Otolithic organs (utricle and saccule) sense
  linear acceleration
                   Embryology
   3rd week of
    embryonic
    development
   Otic placode formed
    from neuroectoderm
    and ectoderm
   Otocyst or otic vesicle
    4th week
   Semicircular canals
    are orthogonal to each
    other
   Lateral canal inclined
    to 30 degrees
   Superior/postereor
    canals 45 degrees off
    of sagittal plane
   Utricle is in horizontal
    plane
   Saccule is in vertical
    plane
Anatomy
   There are five
    openings into area of
    utricle
   Saccule in spherical
    recess
   Utricle in elliptical
    recess
 45% from AICA
 24% superior
  cerebellar artery
 16% basilar
 Two divisions:
  anterior vestibular and
  common cochlear
  artery
   Superior vestibular
    nerve: superior canal,
    lateral canal, utricle
   Inferior vestibular
    nerve: posterior canal
    and saccule
   Membranous labyrinth is surrounded by
    perilymph
   Endolymph fills the vestibular end organs along
    with the cochlea
   Perilymph
     – Similar to extracellular fluid
     – K+=10mEQ, Na+=140mEq/L
     – Unclear whether this is ultrafiltrate of CSF or
       blood
     – Drains via venules and middle ear mucosa
   Endolymph
    – Similar to intracellular fluid
    – K+=144mEq/L, Na+=5mEq/L
    – Produced by marginal cells in stria vascularis
      from perilymph at the cochlea and from dark
      cells in the cristae and maculae
    – Absorbed in endolymphatic sac which
      connected by endolymphatic, utricular and
      saccular ducts
          Sensory structures
 Ampulla of the semicircular canals
 Dilated end of canal
 Contains sensory neuroepithelium, cupula,
  supporting cells
   Cupula is gelatinous
    mass extending across
    at right angle
   Extends completely
    across, not responsive
    to gravity
   Crista ampullaris is
    made up of sensory
    hair cells and
    supporting cells
   Sensory cells are either
    Type I or Type II
   Type I cells are flask
    shaped and have chalice
    shaped calyx ending
   One chalice may synapse
    with 2-4 Type I cells
   Type II cells – cylinder
    shaped, multiple efferent
    and afferent boutons
Hair cells have 50-100 stereocilia and a single
kinocilium.
stereocilia are not true cilia, they are graded in height with tallest
nearest the kinocilium.
             Otolithic organs
 Utricle and saccule sense linear acceleration
 Cilia from hair cells are embedded in gelatinous
  layer
 Otoliths or otoconia are on upper surface
   Calcium carbonate or
    calcite
   0.5-30um
   Specific gravity of
    otolithic membrane is
    2.71-2.94
   Central region of
    otolithic membrane is
    called the striola
   Saccule has hair cells
    oriented away from
    the striola
   Utricle has hair cells
    oriented towards the
    striola
   Striola is curved so
    otolithic organs are
    sensitive to linear
    motion in multiple
    trajectories
   Senses and controls
    motion
   Information is
    combined with that
    from visual system
    and proprioceptive
    system
   Maintains balance and
    compensates for
    effects of head motion
 DEFINITION &
TERMINOLOGIES
           DEFINITION &
          TERMINOLOGIES


   VERTIGO (illusion of rotational, linear or
    tilting movement such as “spinning”,
    “whirling” or “turning” of the patient or the
    surrounding . DISEQUILBRIUM sensation
    of instability of the body positions, walking
    or standing described as “off balanced” or
    “imbalanced”.
            DEFINITION &
           TERMINOLOGIES


   OSCILLOPSIA (inability to focus on
    objects with motion, such as reading a sign
    while walking , seen with bilateral or central
    vestibular loss).
          DEFINITION &
         TERMINOLOGIES


   LIGHTHEADEDNESS (sense of impending
    faint, presyncope).
   PHYSIOLOGIC DIZZINESS (motion
    sickness, height vertigo),
EVALUATION OF THE DIZZY
       PATIENT

                    History
   Dizziness is a term used to describe any of a
    variety of sensation that produce spatial
    disorientation.
   Onset and Duration of Symptoms:
EVALUATION OF THE DIZZY
       PATIENT
                  History

   Character of Dizziness:
   Contributing Factors:
   Associated Symptoms:
    PHYSICAL EXAMINATION

 H & N and General Physical Exam:
 Otoscopy:
 Vestibular Testing:
 Neurological Exam:
      General Characteristics of
   Peripheral and Central Causes of
                Vertigo
Characteristic   Peripheral Central

Intensity             severe          mild

Fatigability          fatigues,       does not
Associated       adaptation fatigue
      General Characteristics of
   Peripheral and Central Causes of
                Vertigo
Characteristic   Peripheral      Central

Symptoms         nausea,              weakness,
                 hearing loss,        numbness
                 sweating             falls more
                                      likely

Eye closed       symptom,            symptoms
                 worse with          better with
                 eyes closed         eyes closed
      General Characteristics of
   Peripheral and Central Causes of
                Vertigo
Characteristic   Peripheral        Central

Nystagmus        horizontal, may       vertical
                 be unilateral         bilateral
                 rotary
Ocular           suppresses            no effect
Fixation         nystagmus (may        or enhances
                 not suppress          nystagmus
                 during acute
                 phase )
    CAUSES OF VERTIGO

PERIPHERAL VERTIGO:
 Benign Paroxysmal Positional Vertigo
 Meniere Disease
 Vestibular Neuronitis
 Perilymphatic Fistulas
    CAUSES OF VERTIGO


CENTRL CAUSES
 Cerebellospontine Angle Tumuors
 Traumatic Vestibular Dysfunction
CENTRAL AND SYSTEMIC CAUSES
         OF VERTIGO


   Multiple Sclerosis
   Other Neurological Disorder (stroke,
    seizures, middle cerebellar lesions,
    parkinsonism, psudobulbar palsy)
   Metabolic Disorders (hypo/hyper-
    thyroidism, diabetes)
CENTRAL AND SYSTEMIC CAUSES
         OF VERTIGO


   Medications and Intoxicants (psychotropic
    drugs, alcohol, analgesics, anesthetics,
    antihypertensives, anti-arrhythmics,
    chemotherapeutics)
   Vascular Causes (vertebrobasilar
    insufficiency, basilar migraine syndrome,
    vascular loop compression syndrome)
 VESTIBULAR TESTING


HALLPIKE TEST
ELECTRONYSTAGMOGRAPHY
ROTATION TEST
OCULOMOTOR TESTING
POSTUGRAPHY
          CALORIC TESTING


 Only test that evaluates vestibular function
  in each ear independently, determines
  unilateral versus bilateral weakness
 Technique:
 Theoretical Normal Response:
           CALORIC TESTING


   Directional Preponderance:
   Unilateral Caloric Weakness:
   Bilateral Weakness:
                DIAGNOSIS

   Based on clinical history, physical
    examination and audiological findings
    (initial low-frequency SNHL) with exclusion
    of other causes of hearing loss and vertigo is
    adequate for diagnosis and initiating
    empirical therapy.
           Meniere’s Disease
            (Endolymphatic
                     Hydrops)
Signs and Symptoms
 Episodic Vertigo lasting minutes to hours
 Episodic fluctuating SNHL (usually unilateral),
  recovery between episodes may be incomplete
  resulting in a progressive SNHL (initially at
  lower frequencies)
 Tinnitus and episodic fullness associated with or
  without the hearing loss
           Meniere’s Disease
            (Endolymphatic
                     Hydrops)

Signs and Symptoms
 Classic Menieres Disease presents with all of the
  above symptoms (vertigo, hearing loss, tinnitus,
  and aural fullness), however Meniere Disease
  may also present as any combination of the above
  symptoms
        Meniere’s Disease
         (Endolymphatic
                  Hydrops)
 DIAGNOSIS
 Vestibular testing may reveal unilateral
  weakness on affected side.
 Electrocochleography:
    MEDICAL MANAGEMENT
     OF MENIERE DISEASE

   Dietary Restrictions:
   Diuretics:
   Vestibular Suppressants:
   Corticosteroids:
   Allergy Management:
   Stress Reduction
BENIGN PAROXYSMAL
POSITIONAL VERTIGO
(BPPV, Cupulolithiasis)
                          BPPV
   Frequency- 50% of peripheral vertigo, 20% of pts over 80
    have BPPV

   Clinical history: sudden onset, brief vertigo, brought on
    by changes in head position, particularly turning in bed,
    or tilting head back, may have prior history of vestibular
    neuritis or head trauma

   Exam: + Dix-Hallpike (don’t forget 5-10% have
    horizontal variant)

   Pathophysiology: loose calcium crystals in posterior
    semicircular canal

   Treatment: Epley manuever
         MANAGEMENT

 Education, reassurance and observation
 Particle Repositioning Maneuver (Epley’s
  Maneuver):
 Home vestibular positional exercises
 Antivertiginous medications
 Singular Neurectomy:
               Vestibular Neuritis
   Frequency: 15% of peripheral vertigo

   Clinical history: sudden onset severe vertigo c N/V, sx’s improve
    in days to weeks secondary to central compensation, can have
    chronic effects for months to years.

   Exam: unilateral nystagmus c fast phase away from affected ear,
    amplitude of nystagmus decreases when looking towards affected
    ear, +/- hearing loss or tinnitus

   Pathophysiology: probably secondary to viral infection &
    inflammation of vestibular nerve or labyrinth

   Treatment: steroids- 3 week tapering course, starting at 100 mg.
     – Strupp et al. (2004). Methylprednisolone, Valacyclovir, or the
       Combination for Vestibular Neuritis. NEJM 351, pp. 354-361.
       PERILYMPH FISTULA

   Pathophysiology:
   Causes:
   SSx:
   Diagnosis:
   Treatment:
      VERTEBRONBASILAR
      INSUFFICIENCY (VBI)

   Pathophysiology:
   SSx:
   Diagnosis:
   Treatment
       OTHER VESTIBULAR
          DISORDERS
   Basilar Migraine Syndrome:
   Vestibular Epilepsy:
   Multiple Sclerosis (MS):
   Labyrinthine Apoplexy:
   Subclavian Steal Syndrome:
   Hyperrinsulinemia/Diabetes:
Etiology Recur Onset   Duration Associated features

BPPV         +    sudden       <1 min     elderly, induced by
                                                       position change
Meniere’s    +   gradual          hours           ear fullness, tinnitus,
                                                 low freq hearing loss
Vestibular   -    gradual       days-weeks 50% c preceding viral
  neuritis       or sudden                     illness, +/- hearing loss
Migraine     +     gradual       sec-days         young F, HA, positive
                                                   visual phenomenon
VB TIA       +    sudden         mins CN, long-tract sx’s/
                                                          signs
Labryinth    -    sudden        days-months              hearing
   stroke                                             loss +/- tinnitus

Brainstem    -   sudden      days-months         CN, long-tract
   stroke                                               sx’s/ signs

Cerebellar   -   sudden      days-months          unil dysmetria,
   stroke                                          “central” nystagmus
    MANAGEMENT CONCEPT

   Safety:
   Acute Vestibular Suppression:
   Vestibular Rehabilitation:
   Surgical Management:
SURGICAL MANAGEMENT
     OF VERTIGO
SURGICAL MANAGEMENT
     OF VERTIGO

   Endolymphatic Sac Surgery:
   Vestibular Nerve Section:
   Transtympanic Or Intratympanic
    Aminoglycoside Injections:
   Labyrinthectomy
Conclusion


1. Is this vertigo?

2. Is this central or peripheral?

3. History- focus on age, PMH, duration

4. Exam- focus on CN and coordination,
     focal neurological findings, Dix-Hallpike

				
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posted:10/18/2011
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