Eye Movements and Dizziness Flashcards
Vertigo
def
illusion of movement: rotation, translation or tilt
Dysequilibrium
def
imbalance while standing or walking; ataxia, proprioceptive or kinesthetic dysfunction, motor dysfunction
Presyncope
def
Lightheadedness, graying out of vision
Psychologic dizziness
types
Confusion: poor concentration, agitation
Giddiness: elation, excitement
Derealization: depersonalization, déjà vu, detachment
Functional classes of human eye movements
Visual fixation
def
Holds an image of a stationary object on the fovea when the head
is stationary
Functional classes of human eye movements
Vestibular
def
Holds images of the seen world steady on the retina during brief head movements
Functional classes of human eye movements
Optokinetic
def
holds images of the seen world steady on the retina during sustained head rotation
Functional classes of human eye movements
Smooth pursuit
def
holds the image of a moving target steady on the retina
Functional classes of human eye movements
Nystagmus quick phases
Reset the eyes during prolonged rotation and direct gaze towards the oncoming visual scene
Functional classes of human eye movements
Saccades
def
Bring images of objects of interest onto the fovea
Functional classes of human eye movements
Vergence
def
Move the eyes in opposite directions so that images of a single object are simultaneously placed on both foveae
Static eye movements
List/fun
(1) Saccade- To acquire target
(2) Vergence- To align eyes on target
(3) Fixation- To hold target
Diplopia is a problem of…
Diplopia, or double vision, is a problem of static eye movements: Failure to align eyes on target and keep them there
Testing static eye movements
Red glass or Maddox rod
(1) The red lens over one eye allows determination of which image comes from each eye. The ribbed lens of the Maddox rod additionally eliminates normal image fusion by vergence.
(2) The patient is asked to look at a light and describe what is seen in each of the 9 directions of gaze, and the result is diagrammed in a tic-tac-toe figure as shown.
(3) Looking toward the weak muscle gives the greatest divergence.
(4) The weak muscle may be a result of a cranial nerve deficit, or due to a problem with the connections between nuclei, as in internuclear ophthalmoplegia, where there is an interruption in the medial longitudinal fasciculus connecting the cranial nerve VI nucleus with the cranial nerve III nucleus.
Dynamic eye movements
list
(1) Vestibular reflex
(2) Optokinetic movement
(3) Nystagmus quick phases
Anatomic parts of vestibular apparatus
A) Saccule and utricle are translational accelerometers
B) Semi-circular canals (SCCare rotational accelerometers)
Parts of vestibular apparatus
Look it up
Do it
Functions of VOR
A) Gain and phase: gain is the degree to which head movement moves the eyes, phase refers to how quickly the response occurs
Oscillopsia
def
Loss of VOR
Connections for lateral eye movements
Excitation at the semicircular canal stimulates the medial vestibular nucleus which stimulates the contralateral sixth nerve nucleus which stimulates the ipsilateral 3rd nerve nucleus via the MLF.
Bedside tests of vestibular function
list
Hallpike-Dix maneuver
Baranys Caloric test
Suppression of fixation
Past pointing
Hallpike-Dix Maneuver
What does it provoke
Provokes severe nystagmus in BPPV or milder nystagmus in other peripheral lesions
Hallpike-Dix Maneuver
How is it done
(1) Have patient turn head 45o to one side and extend neck- this puts the posterior canal on that side in the plane of rotation
(2) Move patient quickly from sitting to lying, letting head hang below horzontal plane- observe for nystagmus for one minute
(3) Move patient quickly back to sitting- observe again for nystagmus for one minute
(4) Repeat with head turned the other way to test the posterior canal on the other side
Caloric Test
How is it done
COWS CUWD
a. Cold water -> nystagmus beating to the opposite side (slow phase toward the ear being tested)
b. Warm water -> nystagmus beating to the same side (slow phase away from the ear being tested)
c. Cold water in both ears -> nystagmus beating upward (slow phase downward)
d. Warm water in both ears -> nystagmus beating downward (slow phase upward)
Suppression of fixation
mech
Suppression of fixation: brings out nystagmus
(1)Use Frenzel goggles or ophthalmoscope while covering the other eye, so patient can keep gaze steady by focusing on a target
Past pointing
mech
(1) Hold one arm extended forwards, swing up to vertical then back down to a target, repeat
(2) Continue repeating this motion with eyes closed. Vertigo will cause drift away from the target.
Peripheral vs central vertigo (chart)
Nystagmus direction/fixation/gaze
Nystagmus direction
Peripheral: Usually mixed (horizontal & rotational)
Central: Usually a single direction
Fixation
Peripheral: Usually suppresses nystagmus
Central:Usually does not suppress nystagmus
Gaze
Peripheral: Nystagmus increases with gaze toward the direction of the quick phase
Central: No change or reverses direction
Peripheral vs central vertigo (chart)
Calorics/balance/Assoc with
Calorics
Peripheral: Little change
Central: Increases
Balance
Peripheral: Mild defect, poor tandem, + past-pointing, (-) Romberg
Central: Severe defects, unable to tandem, +/- past-pointing, + Romberg
Assoc with
Peripheral: May be assoc with hearing loss or tinnitus
Central: Usually no hearing loss or tinnitus, may be assoc with brainstem or cerebellar signs
Episodic Dizziness
Time/chars/dx/rx
1 minute or less
(1) Benign paroxysmal positional vertigo (BPPV)
(2) Etiology: otolith or other debris is loose in semicircular canals (usually posterior)
(3) Dx: Positive Hallpike-Dix maneuver
(4) Rx: Epley’s or Semont’s maneuver
Modified epley’s maneuver (pg. 369)
Mech/alternative
(i) One minute to slowly change positions, four minutes in each postion
(ii) Debris (otoconia) falls into saccule
(iii) Patient then wears a soft collar, no bending, sleeps sitting up for two days while debris adheres, resorbs
Seemont’s Maneuver: not shown but similar, can try if Epley’s fails
Episodic Dizziness
1 hour or less
list/dx/rx
(1) Transient ishemic attack (TIA)
a. Dx: Cerebrovascular & cardiac studies
b. Rx: Reduce risk factors, antiplatelet drugs, CEA
(2) Migraine
a. Dx: International Headache Society criteria
b. Rx: Diet, Sumatriptan, other medications
(3) Panic Attacks
a. Dx: DSM-III R criteria
b. Rx: Benzodiazepines, tricyclics
Episodic Dizziness
Hours to days
List/dx/rx
Meniere’s Syndrome
a. Dx: fluctuating hearing loss, low frequency sensorineural hearing loss, tinnitus
b. Rx: Low salt diet, no caffeine, Diamox, surgery
Vestibular Suppressants
list
Antivertiginous
Antiemetics
Other
Antivertiginous (sedation):
Diazepam
Droperidol
Antiemetics:
Promethazine
Prochlorperazine
Other:
Meclizine
Scopolamine
Management of acute vertigo
Day 1-3
(1) Vestibular suppressants
(2) Bed rest
(3) Hospitalize if dehydrated or if central defect is suspected
(4) Laboratory tests: FTA (fluorescent treponemal antigen for syphilis), ESR (erythrocyte sedimentation rate), rheumatoid factor, ANA (anti-nuclear antibodies for systemic lupus)
(5) MRI
Management of Acute vertigo
subacute
More than 3 days
(1) Stop vestibular suppressants!
(2) Begin vestibular exercises
(3) Laboratory tests: Audiogram, Caloric testing, Rotary chair test
