Visual, Auditory, Vestibular systems Flashcards
presbyopia
age related impairment of near vision
if a pt has difficulty reading the Snellen chart what additional test can you do to see if glasses would correct the problem
have them try to read it when looking through a pin hole.
If that corrects the vision the it is an ocular problem and glasses are needed
what does a acuity problem that does not correct indicate
if it doesn’t correct there may be a lesion of the optic nerve or macula
what is a highly accurate way to record visual fields
using Perimetry, a computer flashes dots of light on the screen and the patient presses a button when seen
what causes the physiologic blind spot
where the optic disk is in the nasal retina since there are no rods or cones there
when may a patients blind spot be enlarged
papilledema
what is papilledema
when increased intracranial pressure causes the optic nerve to appear swollen
what is a scotoma
a pathological, abnormal bind spot (not at the optic disc) in the visual field of one eye where vision is lost or decreased
what causes a scotoma
lesions in the retina (infections, inflammation, macular degeneration, or retinal detachments) or optic nerve (demyelination or ischemia)
what would you call an abnormally narrowed or mall visual field
constricted or contracted visual fields
what could cause a constricted or contracted visual field
glaucoma or a retinal degenerative disease
when is a constricted visual field likely due to a psychiatric problem
if it doesn’t expand in a cone-shaped fashion = tunnel vision
what is a homonymous hemianopsia
a deficit of the nasal half of one eye and the temporal half of the other eye’s visual fields
where is a lesion located that presents with macular sparing
occipital lobe
how does congruence change with the location of a lesion affecting the visual tracts
congruence increased when the lesion is more posterior
what is a heteronymous hemianopsia
a visual deficit involving the nasal halves of bother eyes or the temporal halves of both eyes
where would a lesion causing a heteronymous hemianopsia be located
the optic chiasm
what would someone with a optic chiasm lesions visual fields look like
heteronymous hemianopsia - loss of both temporal visual fields
what is the most common causes of acute unilateral optic nerve lesions
demyelination (MS or ischemia)
how does MS frequently initially present
optic neuritis - may have sudden blindness of part or all of one eye which may feel achy or tender with eye movement, pupils constrict poorly when light is shone in the affected eye but both react normally when light is shone in the other eye
in optic neuritis what is seen on fundoscopic examination
the optic disc appears swollen with indistinct, blurry margins.
exception is retrobulbar neuritis where the inflammation is further back along the optic nerve therefore the disc looks normal
how does optic atrophy appear on fundoscopic exam
optic disc appears more white or pale with sharply defined edges
what is optic atrophy
loss of ganglion cell axons in the optic nerve or optic chiasm - occurs when vision is not restored after optic neuritis
how is optic neuritis differentiated from papilledema
optic neuritis occurs in one eye but papilledema would present in both eyes simultaneously
what other symptoms do patients with papilledema experience
headache, nausea, vomiting, impaired consciousness, vision will not be affected immediately but may become impaired if not treated
how does a pituitary tumor affect vision
pressed on the center of the optic chiasm from below - affects the decussating, inferior, nasal retinal fibers first
what visual field losses are seen with a pituitary tumor
superior temporal quadrants or if there is a total lesion of the optic chiasm a bitemporal heteronymous hemianopsia
what other symptoms besides visual field defects are commonly seen with a pituitary tumor
endocrine symptoms- i.e. hirsutism, galactorrhea, infertility, amenorrhea, coarse feactures, enlarged jaw, nose, tongue, cushing syndrome, impotence, diabetes
what is cortical blindness
severe visual loss from bilateral occipital lobe lesions
what causes a bilateral occipital lobe lesion
thrombosis of the distal basilar artery or emobli down its posterior cerebral artery brances
what other signs are present with cortical blindness
pupillary light reflex is intact and the optic discs appear normal in the retinal ganglion cells are not involved
what is conductive deafness
deafness due to impaired air conduction of sound stimuli
what causes conductive deafness
water or wax in the ear cannel, or fusion or disruption of the bony ossicles (anything before the hair cell receptors)
what is another name for nerve deafness
sensorineural deafness
what causes nerve/sensorineural deafness
damage or impairment of the hair cell receptors or auditory nerve
could be from drug toxicity or persistant exposure to loud noise
what kind of deafness is associated with low tone hearing loss
conductive deafness
what kind of deafness is assocaited with high tone hearing loss
nerve (sensorineural) deafness
what causes severe unilateral deafness
CN VII lesion (more proximal ascending auditory pathways are bilaterally represented)
what type of conduction is typically more efficient
air conduction is normally more efficient than bone conduction
describe the Weber test
hold the tuning fork at the top of the skull or forehead
what would result from a Weber test if nerve deafness had occured in one ear
since both air and bone conduction would be impaired the affected ear the tuning fork is better heard in the normal ear
what would occur if a Weber test was done on someone with conductive deafness in one ear
the vibrating tuning fork is heard better in the deaf ear, since bone conduction is enhanced
describe the Rinne test
begin by holding the vibrating tuning fork on the mastoid bone allowing the vibration to be heard by bone conduction. When it is no longer heard move it to next to the ear where it should still be normally heard (since air conduction is better than bone conduction)
what is the result of the Rinne test in someone with conduction deafness
air conduction is no longer more efficient than bone conduction therefore the tuning fork would not be heard when moved off the mastoid bone
what is the result of the Rinne test in partial nerve deafness
since air conduction is still better than bone conduction the tuning fork would be heard when moved off of the mastoid
if a Weber test is louder in the right ear what are the possible defects
either Right conductive deafness or LEFT nerve defect
what is an electronystagmorgram (ENG)
uses special equiptment to record eye movements and nystagmus induced by currents of warm or cold air entering the external ear canal and determines whether the right or left vestibular system is impaired
How is a Dix-Hallpike maneuver preformed
patient lies supine on the examination table with his or her head tilted about 45 degrees below the edge of the table turned to the side.
what is being tested by the Dix-Hallpike maneuver
the posterior semicircular canal of the tilted lower ear.
if this position creates rotatory nystagmus then that posterior semicircular canal is overly sensitive to head movement and is the cause of the vertigo
what are 2 possible causes of acute severe unilateral deafness
- trauma - particularly petrous bone fractures
* ischemia - in the territory of the anterior inferior cerebellar artery (AICA)
what is acute labyrinthitis
when the labyrinth of the inner ear is affected by a viral infection or inflammation causing severe vertigo with nausear and vomiting, hearing impairment and unsteadiness of gait
what 3 things are commonly found on examination of a patient with acute labyrinthitis
nystagmus, unilaterally decreased hearing, and gait ataxia
what is Meniere’s disease
recurrent episodes of vertigo deafness and tinnitis
what causes Meniere’s disease
the membranous labyrinth swells and ruptures allowing potassium-rich endolymph to leak into the surrounding perilymph, disrupting the ionic gradient required for normal hair cell function
what is the prognosis of Meniere’s disease
the repetitive episodes may lead to complete, permanent deafness - the risk may be decreased by dietary salt reduction and diuretics (decrease the production of endolymph)
who is most likely to experience benign positional vertigo
elderly patients
what causes benign positional vertigo
degeneration of otoliths and displaced calcium crystals and other debris that lodges around the cilia of semicircular canal hair cells making them oversensitive to minor movements of the head
