vestib - objective exam Flashcards
what are the 5 main components of the vestib objective exam
- oculomotor exam
- head thrust / head impulse test
- head shaking induced nystagmus test
- dynamic visual acuity test (DVA)
- positional testing of SCC
what are 8 things to look at in the oculomotor exam
ocular alignment
EOM
smooth pursuits
saccades
vergence
GEN
spontaneous nystagmus
VORc
what are 4 types of misalignments seen in resting eye position
esotropia
exotropia
hypotropia
hypertropia
ocular alignment: normal vs abnormal (and likely cause)
normal: position symmetrical
abnormal: misalignment
- spontaneous nystagmus (peripheral or central lesion)
what is the function of normal EOM
eyes move in concert
-> brain takes input from each and puts it together to form a single image
what is the test to screen EOM
test 6 cardinal positions in H pattern holding tip of finger 18-24in from eyes
EOM: normal vs abnormal (and likely cause)
normal: able to follow target thru full range
abnormal: dec mobility in eye
- CN III, IV, VI lesion
- potential lesion of parietal/occipital lobe, pons, cerebellum
what does smooth pursuits measure
person’s ability to accurately track a visual target in a smooth controlled manner
- looking for coordination
what is the task for smooth pursuits
single point target held parallel to ground 18-24in from eyes
- person follows single point target as slowly moves horizontally and vertically
smooth pursuits: normal vs abnormal (and likely cause)
normal: accurately track visual target in smooth controlled manner w both eyes
- eyes remained fixated on moving object
abnormal: eye mvmt not controlled
- consistent saccadic intrusions
- GEN (closer to end range)
(+) central dysfunction
what are saccades
normal rapid, ballistic mvmts of eyes that abruptly change point of fixation
- amplitude of mvmt changes depending on task
how are saccades tested/assessed
person repeatedly change gaze fixation from one target to another
- assessed both horizontally and vertically
saccades: normal vs abnormal (and likely cause)
normal: eyes should be conjugate, have normal amplitude and brisk velocity
abnormal: consistently overshoots (hypermetric) or undershoots (hypometric) w multiple small saccades to get to target
*(+) central path
what is vergence and how is it tested
simultaneous mvmt of both eyes in opposite directions to obtain or maintain single binocular vision
person focuses on tip of finger while slowly moves toward pt nose
vergence: normal vs abnormal (and likely cause)
normal: eyes should converge symmetrically and pupils should constrict
- NPC <4’’
abnormal: eye mvmt asymmetrical
- NPC >4’’
*(+) indicate central path
- some people show ocular deviation at baseline, 6% of gen pop has convergence insufficiency
what is spontaneous nystagmus
nystagmus at rest w fixed gaze
why are frenzel lenses a good tool to utilize when testing for spontaneous nystagmus
help to block out light
- makes it so pt can’t fixate on object to suppress nystagmus -> CNS can suppress peripheral causing spontaneous nystagmus by fixating on target
also makes eyeballs larger to more accurately identify mvmt
what is spontaneous nystagmus a key clinical sign in
pts w acute vestibular syndrome (AVS)
what are causes of spontaneous nystagmus and what are ways to diff dx
acute unilateral peripheral hypofunction
- dec w gaze fixation
- resolves w/i 3-7days
central lesion (brainstem, cerebellar abnormality)
- doesn’t dec w gaze fixation
- doesn’t resolve w/i days and is chronic in nature
what is rebound nystagmus
keeps going back and forth w/o a slow or fast beat phase
how is GEN/holding nystagmus assessed
watch pt in primary gaze and then in lateral gaze (usually 30deg to each side)
- assess direction and # of beats
GEN: normal vs abnormal
normal: <1-2 beats in end range
- present in >50% of gen pop w normal vision
- GEN normal in people >65yo bc eye ms lose ability to tonically hold end range
abnormal: sustained GEN > 2 beats
GEN of a central vs peripheral origin
central: dominant characteristic is direction changing nystagmus, pure vertical/torsional
- could be rebound
peripheral: consistently beats away form affected side (toward intact side)
- non-direction changing
- can be torsional
- may be suppressed w gaze fixation
what is VOR cancellation and how is this assessed
in order to shift direction of gaze along w head motion, VOR needs to be overridden/cancelled
assess person’s ability to maintain fixation on target while head and target are moving
VORc: normal vs abnormal (and likely cause)
normal: can maintain visual fixation w/o c/o blurriness
abnormal: saccadic eye mvmts/intrusions (eyes move off target, eyes jump back to target)
- person c/o blurriness
*(+) central dysfunction
what are tests for the VOR and what do abnormal results of these tests usually indicate
head thrust/impulse test
head shaking induced nystagmus
dynamic visual acuity
unilateral vestib hypofunction
- aka peripheral dysfunction
indication of CNS vs PNS involvement in abnormal VOR findings
CNS = vertical nystagmus
PNS / vestib hypofunction
- horizontal nystagmus
- beat away from affected side
dynamic visual acuity: normal vs abnormal (and likely cause)
normal: 2-line or less difference b/w static and dynamic visual acuity
abnormal:
UVH >3 line loss
BVH > 5 line loss
how is the head thrust/impulse test helpful for diff dx
helpful to r/o stroke d/t high specificity/sensitivity to detect vestib hypofunction
what are 2 important considerations in performing a head thrust / impulse test
head flex forward 20-30deg to level horizontal canals
high acceleration thrusts to kick in VOR
head thrust: normal vs abnormal (and likely cause)
normal: vision fixation maintained
abnormal: corrective saccades after head rotation inability to maintain visual fixation
(+) peripheral hypofunction on side head turned toward during testing
- (+) thrust R, corrective L saccade = R UVH
- (+) thrust R and L = BVH
what is an important consideration if you want to perform a head shaking induced nystagmus test
only performed w fixation blocked (ie Frenzel lenses)
procedure for head shaking induced nystagmus test
head flex down 30deg, eyes closed, head rapidly oscillated by PT 20xs
- cued to open eyes just prior to stopping head motion and observe for nystagmus
head shaking induced nystagmus: normal vs abnormal (and likely cause)
normal: none or 1-2 beats
abnormal: >/= 3 beats
- existing nystagmus accentuated
- usually beats to intact side
what do the presentations of head shaking induced nystagmus indicate
beats L = R UVH
beats R = L UVH
vertical nystagmus = central vestib
