midterm Flashcards
common causes of vestibular disorders
head trauma, otitis media, bacterial labyrinthitis or vestibular neuronitis, viral labyrinthitis or vestibular neuronitis, ototoxic medications, ischemia, vestibular schwannoma or viral causes
impact of dizziness and balance on the population
dizziness is the 3rd most common complaint within outpatient clinics and the #1 complaint in individuals over the age of 70
-additionally, half of the people over the age of 70 will experience BPPV
how is dizziness often reported by our patients
vertigo, syncope, lightheadedness, disequilibrium, unsteady, floating, rocking, tilting, foggy feeling, motion sickness, etc.
true vertigo
the room is spinning or you are spinning
-all about rotation
the ability to maintain balance depends upon ….
sensory information gathered from visual, somatosensory and vestibular receptors within the body
-the sensory information is picked up and set to the brainstem for integration and then sent up to the cortex for perception and processing
how do the cerebellum and cerebral cortex streamline the balance process
they coordinate incoming impulses and add that information from thinking and memory
peripheral vs. central
inner ear (labyrinth to the brainstem) vs. the CNS (brainstem to the cortex)
vision denied
patient does not have a visual target, eyes are closed or covered
vision allowed
patient has a visual target, eyes are open or uncovered
role of the peripheral vestibular system
allows us to interact and maintain contact with our surroundings in a safe, efficient manner
the labyrinth
interconnected canals and cavities that are located in the petrous portion of the temporal bone that houses the sensory organs
bony labyrinth vs. membranous labyrinth
the outer wall vs. inside the bone and suspended in fluid
perilymph vs. endolymph
fluid within the labyrinths that is similar to CSF vs. fluid inside of the membranous labyrinth
how many sensory structures are there total
10 ; 5 on each side
-3 SCC, 1 utricle and 1 saccule
semicircular canals (SCC) overview
bony tubes that are interconnected and oriented as right angles of each other allowing the endolymph to flow to or from the ampullated end of the canal
-3 per canal
-responsible for the pitch, yaw and roll movement
SCCs are primarily responsible for detecting ……
angular accelerations and decelerations of the body
the sensory cells of the SCCs are the …..
cristae ampullaris
what is the cupula and what is happens if the density is changed
it sits on top of the cristae containing the same density as the endolymph
-if anything that impacts the density, this will cause an illusion of vertigo due to stimulation
vestibular hair cells
these are stimulated by the movement of the SCC and the position relative to gravity
-they have kinocilium and several stereocilia containing a resting potential when at rest but with any motion this will change the potential
any movement that causes the sterocilia to flow towards the kinocilium results in ……
depolarization with an increased potential
any movement that causes the sterocilia to flow away from the kinocilium results in ……
hyperpolarization with a decreased potential
how are vestibular hair cells oriented in the SCC canals
in anterior and posterior : towards the canal side of the ampulla
in horizontal : towards the utricle
how does the horizontal canal become inhibited and excited
movement of endolymph away from the ampulla causes inhibition and movement towards the ampulla causes excitation
how does the anterior and posterior canals become inhibited and excited
movement of endolymph towards the ampulla causes inhibition and movement away from the ampulla causes excitation
overview of the otolithic/macular organs
gelatinous structures with otoconia embedded on top that detects movement
-including both the utricle and saccule
otolithic organs are primarily responsible for detecting ……
gravitational acceleration and the perception of up/down movement
the sensory structures of the otolithic organs are ….
otoconia
what are otoconia and what role do they play besides being the sensory structures
calcium carbonate crystals that cause weight
-with any movement relative to the support structures, this results in stimulation of these cells
with the otoconia, when do problems occur
if they move into the SCCs
-results in gravity sensitve structures in areas not senitive to gravity
with otolithic organs, they stay stimulated for …..
longer
-as long as there is movement they will be stimulated
the utricle plays a role in ….
postural control and senses change in orientation with respect to gravity
the saccule plays a role in ….
changes in orientation within the vertical plane
how are the vestibular hair cells oriented within the utricle and saccule
oriented towards the striola within the utricle and away from the striola in the saccule
branches of the vestibular nerve
superior : in the utricle, anterior part of the saccule and the horizontal and anterior canal
inferior : in the posterior part of the saccule and the posterior canal
3 functions of the vestibular system
to provide a subjective sensation of movement and/or displacement in 3D space, to maintain upright body posture and to stabilize the eyes during head/body movement
what are the 3 vestibular reflexes that help the 3 functions
vestibulo-ocular reflex (VOR), vestibulo-collic reflex (VOC) and the vestibulospinal reflex (VSR)
function of the VOR
giving a clear image through generating reflexive movements that are equal to and opposite of the head movement
what occurs if the VOR is damaged
oscillopsia or retinal slip
-visual field is bouncing when you walk
-retinal slip will result in corrective saccades
how can we quickly assess the VOR
head thrust/head pulse
how do the eye muscles correlate with a cranial nerve
CN 3 : medial rectus, superior rectus, inferior rectus and inferior oblique
CN 4 : superior oblique
CN 6 : lateral rectus
what occurs when the eyes reach their limit
when the eyes reach their width limit, the CNS causes the eyes to move back to the center in order to create a new focal point through a saccade
function of the vestibulo-collic reflex (VCR)
acts on the neck musculature to stabilize the head helping to keep the head in the horizontal gaze point relative to gravity
-maintaining upright head position
how to assess the VCR
cVEMP
function of the vestibulospinal reflex (VSR)
generates compensatory body movement to maintain head and postural stability in the upper and lower limbs that is activated from the neck down
-stabilizes body movement
how to assess the VSR
postural stability exams
what occurs if the VSR is damaged
patients could be walking or bending the opposite way
what are some bedside screening evaluations we can conduct
romberg, fukuda, halmalgi head thrust, active or passive head shake and dynamic visual acuity
romberg/tandem romberg
screens the body’s proprioception (somatosensory) system and the degree of functional disequilibrium caused by central vertigo, peripheral vertigo and head trauma
how to complete the romberg/tandem romberg
have the patient stand with their feet together and arms out to the side, ask them to stand still for 10-15 seconds (eyes open then closed)
-to make it a tandem, have the patient put the feet in front of each other
results of the romberg/tandem romberg
positive romberg : if the patient sways or falls or with any non fluid motions
-patients will generally move towards the side of the problem
fukuda/stepping fukuda
measures the labyrinth function through vestibulospinal reflexes
how to complete the fukuda/stepping fukuda
have the patient hold their arms out straight and ask them to march in place for 50 steps with their eyes closed
results of the fukuda/stepping fukuda
normal : able to complete the task without significant angular deviation
abnormal : patient will rotate and is considered positive if the rotation exceeds 45 degrees
halmalgi head thrust
measures the SCC dysfunction in all canals and the detection of peripheral vestibulopathy
how to complete the halmalgi head thrust
hold the patients head and slowly move it side to side at first then use a rapid pattern to move the head to each side, ask the patient to keep their eyes open throughout the test, head should be held briefly at the end of the impulse to monitor for re-fixation saccades
results of the halmalgi head thrust
normal : no corrective saccades
abnormal : refixation/corrective saccades present
active/passive head shake
evaluates the status of the patients velocity storage integrator
-identifying if function is balanced
how to complete the active/passive head shake
have the patients eyes under the goggles or eyes closed, shake the patients head back and forth and after 20 seconds ask them to open their eyes and not if any nystagmus is observed
results of the active/passive head shake
normal : no post headshake nystagmus
abnormal : post headshake nystagmus present or enhanced post headshake nystagmus
result pattern with the active/passive head shake
no pre and no post HS : balanced function
no pre but present post HS : unbalanced vestibular function
present pre and increased post HS : asymmetry but we made it greater, newer condition
present pre and present HS : central funding
dynamic visual acuity (passive head rotation with snellen chart)
screens for oscillopsia that is a complaint often caused by vestibular loss
-looking at the VOR
how to complete the dynamic visual acuity
have the patient a proper distance from eye chart and have them read the lowest line that they can, when completed shake the head back and forth and have the patient read the lowers line possible during the rotation
-observe the line change
results of the dynamic visual acuity
normal : no line change or just a slight line change (normal VOR function)
abnormal : having a line change of 2 or greater (no laterality)
nystagmus
involuntary rhythmic oscillation of the eye with many different types and description
-can be either pathological or physiological
slow phase
describes the magnitude of the nystagmus
-generated by the vestibular system, driven by the ears
-occurs within 5 to 10 msec
fast phase
describes the direction of the nystagmus
-generated by the central system, driven by the CNS
-occurs within 70 msec
how can we assess nystagmus
oculography with VNGs, rotational tests, head thrust or vHIT
nystagmus will beat __________ a stimulated ear and __________ from an inhibited ear
towards ; away
nystagmus will generally beat _______ from the impacted side
away
with unilateral damage, there will be a weak side and there is no ability to have excitation resulting in ….
perceived spinning
-the strong side drives the vestibular activity against the weak side
with bilateral and equal vestibular deficits the patient would not perceive vertigo but would more often complain about …
feeling off balance
-therefore the patient would not have nystagmus based on asymmetry
pendular nystagmus
speed of motion is the same in both directions, appearing sinusoidal
-identifying the speed by cycles per second (magnitude)
jerk nystagmus
speed of motion is seen within a slow and fast phase, moving opposite of each other
-identifying the speed by the slope
with a central lesion, how does the nystagmus typically change with a fixation
will either stay the same or become enhanced
with a peripheral lesion, how does the nystagmus typically change with a fixation
will decrease
downbeating nystagmus
fast phase is down and the slow phase is going up
upbeating nystagmus
fast phase is up and the slow phase is going down
alexander’s law
a enhancement of nystagmus when the patient looks the same way of the beating and then a decrease or elimination in the opposite way
-the patient needs to have central gaze nystagmus for this to occur
alexander’s law is typically seen in the ______ stages of vestibular disorders
early
torsional or rotary nystagmus
the eyes rotate about the central axis of the globe
-pure torsional is a sign of central but if seen within positional testing indicates a more peripheral finding
gaze evoked nystagmus
elicited by the attempt to maintain an ecentric gaze
-becomes present when you move the eyes away from the center gaze
-will observe a corrective saccade
acquired jerk nystagmus
the intensity of nystagmus increases with gaze towards the fast phase and decreases or reverses directions upon gaze in the direction of the slow phase
physiologic (end point) nystagmus
occurs when the patient is asked to stare at a target out on the side for 30 seconds or more, causing the eyes to be tired and therefore resulting in nystagmus
-occurs with gazes that are too wide and too long
what are three types of nystagmus that are considered normal
fatigue nystagmus, unstained end point nystagmus and sustained end point nystagmus
geotropic nystagmus
beating towards the floor
ageotropic nystagmus
beating away from the floor
what are the three eye recording techniques
electro-oculography (ENG/EOG), infrared video oculography (VOG/VNG) and scleral search coils
electro-oculography (ENG/EOG)
we are recording the corneo-retinal potential (CRP)
-this potenital is altered when the eyes look in either direction
reasoning of the electro-oculography (ENG/EOG)
the eye has dipolar orientation and the retina is negatively polarized causing a steady electrical potential field that can be detected if the eyes are closed or in darkness
-with any rotation of the eye, it will bring a change of polarity which is recorded
-therefore the relative voltage difference caused by the eye movement provides the basis of the EOG
any eye movement to the right will cause a recording to deflect ________ ; any eye movement to the left will cause a recording to deflect _________
upward ; downward
infrared video oculography (VOG/VNG)
uses pupil localization technology and the reflective nature of the corneal surface to calculate the pupil location and angle
-the goggles contain the infrared diode to illuminate the eyes
scleral search coils
coils that are embedded into a tightly fitted contact lens or a rubber ring that adheres to the eye
-there are alternating magnetic fields that are generated by magnets positioned around the eye and through electromagnetic induction
with any vestibular testing, what it is a test of
function rather than strucure
what is the purpose of a vestibular assessment
to determine if the symptoms are caused by the inner ear, brain or both
what are pre-test instructions for a VNG
patients are refrained from taking certain medications for at least 12 hours prior, refrained from drinking alcoholic beverages, not eating a big meal prior, wear comfortable clothing and to remove eye makeup for testing
why are medications often asked to not be consumed before a VNG
some medications can interfere with the accuracy of the recording and some pain medications can cause drowsiness impacting the recording
what are the components of a vestibular case history that we are wanting to ask
description, timing, frequency, provoking factors, associated symptoms, any other medical history, medications and other relevant topics in regards to the patient
the most common test for evaluation of dizziness if the ENG/VNG, what are the components of this testing
oculomotor evaluation, positional/positioning evaluation and caloric irrigation
BPPV
the most common cause of vertigo in the elderly and the most common cause of vertigo that we see in all patients
-based on the movement of otoconia
-2 potential causes canalithiasis and cupulolithiasis
canalithiasis
otoconia are moving freely in the endolymph
-will see a delayed onset with fatigue over time
cupulolithiasis
otoconia get stick to the cupula
-will show immediate onset with little to no fatigue over time
in order to diagnosis BPPV, what criteria must be present
latency (beginning 1 or more seconds after head tilt), duration of at least 1 minute, linear rotational nystagmus, reversal observed when sitting and fatiguability over time
mechanisms of BPPV
otoconia become detached from their otoconial layer by degeneration or head trauma or viral infection and they become settled into the SCCs
-this results in gravity sensitive organs to be in a place of acceleration movement causing the symptoms
what is the most common canal to have BPPV with, what is the least common
posterior ; anterior
if BPPV is bilateral, how do we classify it
on the worse side
