Disorders of the Vestibular and Visual Systems Flashcards
What is vertigo?
An illusion of motion
*most common symptom of vestibular system disorder
What does vertigo arise from?
a disturbance of spatial orientation in the vestibular cortex
Vestibular disorders may cause ______ nystagmus
pathologic
Does pathologic nystagmus fatigue and habituate in periperhal or central disorders?
in most peripheral disorders, but not in central disorders
What does a complete lesion affecting receptors or cranial nerves dedicated to that system produce?
a total ipsilateral loss of sensory input for the particular system
What does a complete lesion in the retina or optic nerve cause?
ipsilateral blindness in the visual system
Do peripheral or central disorders typically cause recurring periods of vertigo and more severe nausea?
Peripheral vestibular disorders
What always accompanies peripheral vertigo?
nystagmus
What are 2 other symptoms of vestibular disorders?
- diminished hearing
- tinnitus
What are 5 common peripheral vestibular disorders?
- benign paroxysmal positional vertigo (BPPV)
- vestibular neuritis
- Ménière’s disease
- traumatic injury
- perilymph fistula
What benign paroxysmal positional vertigo (BPPV)?
An inner ear disorder that causes acute onset of vertigo and nystagmus
BPPVs are benign meaning….?
Paroxysmal meaning…?
Positional meaning…?
- Benign: Is not malignant.
- Paroxysmal: Has a sudden onset of a symptom or disease.
- Positional: Denotes head position as the provoking stimulus.
Rapid change of head position, resulting in vertigo and nystagmus, will subside in less than _ minutes, even if the provoking head position is sustained.
2
What are 4 activities that frequently provoke BPPV?
- Getting into or out of bed
- Bending over to look under a bed
- Reaching up to retrieve something from a high shelf
- Turning over in bed
What causes BPPV?
the displacement of otoconia from the macula into a semicircular canal
Signs and symptoms of BBPV can be provoked using the _____ maneuver.
Hallpike
The displacement of otoconia may occur spontaneously or it may be the result of what?
trauma or infection of the vestibular apparatus
What is Vestibular Neuritis?
Inflammation of the vestibular nerve
What usually causes Vestibular Neuritis?
a virus
What are the symptoms of Vestibular Neuritis?
- dysequilibrium
- spontaneous nystagmus
- nausea
- severe vertigo
Is hearing affected in Vestibular Neuritis?
no
What is Ménière Disease?
A disease that causes a sensation of fullness in the ear, tinnitus, severe acute vertigo, nausea, vomiting, and hearing loss
What is Ménière Disease associated with?
Abnormal fluid pressure in the inner ear
Traumatic injury may cause what 3 things to occur which may alter the vestibular system?
- concussion of the inner ear
- fractures of the bone surrounding the vestibular apparatus and nerve
- pressure changes in the inner ear
What is perilymph?
fluid in the space between the bone and the membranous labyrinth in the inner ear
A perilymph fistula is the result of what?
An opening between the middle and inner ear which allows perilymph to leak from the inner ear into the middle ear
What does a perilymph fistula produce?
- abrupt onset of hearing loss
- tinnitus
- vertigo
What is oscillopsia?
the subjective sensation of visual objects bouncing when the head is moving or the persons is walking
Oscillopsia tends to occur because normal reflexive adjustments for head movement are _______.
decreased
Oscillopsia is the initial complaint of what?
Bilateral Lesionsof the Vestibular Nerve
Central Vestibular Disorders are the result of what?
damage to the vestibular nuclei or to the connections within the brain
Central Vestibular Disorders are most commonly the result of what 4 things?
- ischemia or tumors in the brainstem/cerebellar region (e.g., Wallenberg’s syndrome)
- cerebellar degeneration
- multiple sclerosis
- Arnold-Chiari malformation
What may also cause vestibular dysfunction?
Migraine headaches
What does unilateral vestibular loss cause problems with?
- posture
- eye movement control
- nausea
Peripheral lesions interfering with otolithic function on one side causes imbalance which produces a tendency to fall _____ the side of the lesion.
toward
A unilateral lesion affecting the otoliths or the vestibular nuclei may produce what?
An ocular tilt reaction
What does bilateral vestibular loss eliminate?
A person’s internal sense of gravity
What must a person with bilateral vestibular loss relay on for spatial orientation?
visual and proprioceptive cues
IS vertigo present in bilateral vestibular loss? Why or why not?
No, because there is no asymmetry of the vestibular information
Bilateral loss of semicircular input causes failure of which reflex?
VOR
When a person with bilateral vestibular loss walks, what happens?
the world appears to bounce up and down
What is a common symptom of individuals with chronic vestibular dysfunction?
stiffness of the neck and shoulders, due to attempting to stabilize the head to lesson vertigo or oscillopsia.
Visual losses are clinically described by referring to the “_______________”.
“visual field deficit.”
What is anposia?
Loss of sight in one or both eyes
What is hemianopsia?
Loss of sight in one half of the visual field
What is homonymous hemianopsia?
Loss of vision in the left or right visual field of both eyes
A lesion of the optic nerve will cause what?
loss of vision from the ipsilateral eye
A lesion of the optic chiasm will cause what?
bitemporal hemianopsia
A lesion of the optic tract will cause what?
loss of vision from the contralateral visual field of both eyes (homonymous hemianopsia)
Describe a person who is cortically blind
They have no awareness of any visual information
What is blind sight?
the ability of an individual who is cortically blind to orient or point to visual objects
How can a person who is cortically blind orient their head position?
Because the ability to perceive light and dark is vaguely retained in the visual system
The ability of a cortically blind person to orient to visual objects is contingent on what?
Intact function of the retina and pathways from retina to superior colliculus
Abnormalities of eye movement occur with lesions involving what 6 things?
- Cranial nerves that control extraocular muscles
- Strength of extraocular muscles
- Medial longitudinal fasciculus
- Vestibular system
- Cerebellum
- Eye fields in the cerebral cortex
What are tropia and phoria?
deviations of the ability to align the eyes
Define tropia
the deviation of one eye from a forward gaze when both eyes are open
Define phoria
the deviation from a forward gaze, apparent only when the person is looking forward with one eye, while the other eye is covered.
What is motion sickness?
Nausea, headache, anxiety, and vomiting experienced in moving vehicles
What may cause motion sickness?
A conflict between different types of sensory information or by postural instability.
What may cause seasickness?
A conflict between visual and vestibular information
When a patient reports dizziness what 4 things must the clinician distinguish among?
- Vertigo: illusion of movement (vestibular disorder)
- Near syncope: feeling of impending faint (cardiovascular)
- Dysequilibrium: loss of balance (usually neurologic)
- Light-headedness: inability to concentrate (psychological such as anxiety disorder)
What is the most important question to answer if the patient has a vestibular disorder?
Whether the lesion is peripherally or centrally located
Postural tests are classified as one of what 2 types of tests? Give an example of each
- Static: Romberg’s test
- Dynamic: tilt boards
Which coordination test examines lower limb coordination?
Tandem walking and the heel-to-shin test
What is sensory ataxia characterized by?
It is characterized by impaired vibratory and position sense, decreased or lost ankle reflexes, a lack of nystagmus, and a lack of vertigo.
What is cerebellar ataxia characterized by?
The inability to stand with feet together, regardless of whether the eyes are open or closed. Vertigo and nystagmus may be associated.
When is cerebellar ataxia evident?
All of the time, regardless of whether the person is standing, sitting, or lying down.
When is vestibular ataxia evident?
When walking; limb movements are normal when lying down
What is sensation testing used for?
to localize a lesion
What 3 senses are tested during sensation testing?
Hearing, proprioception, and vibration
What are proprioception and vibration tests used to distinguish between?
lesions of the conscious proprioception pathways and vestibular lesions
When performing the Hallpike maneuver, if the left ear, rotary nystagmus is _______; if the right ear is affected, rotation is ________.
clockwise
counterclockwise
What are 5 ways in which Vestibulo-Ocular Reflexes are tested?
- Passive, rapid head thrusts
- Testing dynamic visual acuity
- Using a rotating chair
- Caloric testing
- Electronystagmography
Describe how a caloric test is performed
A small amount of cold (30° C) or warm (44° C) water is instilled into the ear canal.
- In a conscious patient, the mnemonic COWS summarizes the saccadic movements of the eyes: cold opposite, warm same
- Nausea and vomiting may result from the vestibular action on autonomic function.
What is Electronystagmography?
a recording of eye movements
The ability to direct gaze can be tested by which 3 tests?
- Cover test
- Cover-uncover test
- Alternate cover test
What are rehab exercises designed to promote?
movement retraining, habituation, or substitution to improve function
