Eye Movements and Dizziness

Question 1

Vertigo

def

Answer 1

illusion of movement: rotation, translation or tilt

Question 2

Dysequilibrium

def

Answer 2

imbalance while standing or walking; ataxia, proprioceptive or kinesthetic dysfunction, motor dysfunction

Question 3

Presyncope

def

Answer 3

Lightheadedness, graying out of vision

Question 4

Psychologic dizziness

types

Answer 4

Confusion: poor concentration, agitation
Giddiness: elation, excitement
Derealization: depersonalization, déjà vu, detachment

Question 5

Functional classes of human eye movements

Visual fixation

def

Answer 5

Holds an image of a stationary object on the fovea when the head
is stationary

Question 6

Functional classes of human eye movements

Vestibular

def

Answer 6

Holds images of the seen world steady on the retina during brief head movements

Question 7

Functional classes of human eye movements

Optokinetic

def

Answer 7

holds images of the seen world steady on the retina during sustained head rotation

Question 8

Functional classes of human eye movements

Smooth pursuit

def

Answer 8

holds the image of a moving target steady on the retina

Question 9

Functional classes of human eye movements

Nystagmus quick phases

Answer 9

Reset the eyes during prolonged rotation and direct gaze towards the oncoming visual scene

Question 10

Functional classes of human eye movements

Saccades

def

Answer 10

Bring images of objects of interest onto the fovea

Question 11

Functional classes of human eye movements

Vergence

def

Answer 11

Move the eyes in opposite directions so that images of a single object are simultaneously placed on both foveae

Question 12

Static eye movements

List/fun

Answer 12

(1) Saccade- To acquire target
(2) Vergence- To align eyes on target
(3) Fixation- To hold target

Question 13

Diplopia is a problem of…

Answer 13

Diplopia, or double vision, is a problem of static eye movements: Failure to align eyes on target and keep them there

Question 14

Testing static eye movements

Red glass or Maddox rod

Answer 14

(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.

Question 15

Dynamic eye movements

list

Answer 15

(1) Vestibular reflex
(2) Optokinetic movement
(3) Nystagmus quick phases

Question 16

Anatomic parts of vestibular apparatus

Answer 16

A) Saccule and utricle are translational accelerometers

B) Semi-circular canals (SCCare rotational accelerometers)

Question 17

Parts of vestibular apparatus

Look it up

Answer 17

Do it

Question 18

Functions of VOR

Answer 18

A) Gain and phase: gain is the degree to which head movement moves the eyes, phase refers to how quickly the response occurs

Question 19

Oscillopsia

def

Answer 19

Loss of VOR

Question 20

Connections for lateral eye movements

Answer 20

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.

Question 21

Bedside tests of vestibular function

list

Answer 21

Hallpike-Dix maneuver

Baranys Caloric test

Suppression of fixation

Past pointing

Question 22

Hallpike-Dix Maneuver

What does it provoke

Answer 22

Provokes severe nystagmus in BPPV or milder nystagmus in other peripheral lesions

Question 23

Hallpike-Dix Maneuver

How is it done

Answer 23

(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

Question 24

Caloric Test

How is it done

Answer 24

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)

Question 25

Suppression of fixation mech

Answer 25

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

Question 26

Past pointing mech

Answer 26

(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.

Question 27

Peripheral vs central vertigo (chart) Nystagmus direction/fixation/gaze

Answer 27

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

Question 28

Peripheral vs central vertigo (chart) Calorics/balance/Assoc with

Answer 28

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

Question 29

Episodic Dizziness Time/chars/dx/rx 1 minute or less

Answer 29

(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

Question 30

Modified epley’s maneuver (pg. 369) Mech/alternative

Answer 30

(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

Question 31

Episodic Dizziness 1 hour or less list/dx/rx

Answer 31

(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

Question 32

Episodic Dizziness Hours to days List/dx/rx

Answer 32

Meniere’s Syndrome a. Dx: fluctuating hearing loss, low frequency sensorineural hearing loss, tinnitus b. Rx: Low salt diet, no caffeine, Diamox, surgery

Question 33

Vestibular Suppressants list Antivertiginous Antiemetics Other

Answer 33

Antivertiginous (sedation): Diazepam Droperidol Antiemetics: Promethazine Prochlorperazine Other: Meclizine Scopolamine

Question 34

Management of acute vertigo Day 1-3

Answer 34

(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

Question 35

Management of Acute vertigo subacute More than 3 days

Answer 35

(1) Stop vestibular suppressants! (2) Begin vestibular exercises (3) Laboratory tests: Audiogram, Caloric testing, Rotary chair test