Visual, Auditory and Vestibular Systems Flashcards
Visual acuity:
How is it tested?
What does it test?
Interpret 20/100:
Visual acuity pertains to the smallest row of numbers or letters a patient can accurately read
Each eye is tested separately, reading the smallest size of numbers/letters on a Snellen wall chart
it is a function of central vision involving the macula
It is recorded as a fractional number, which compares the patients vision with the normal populations.
20/100 = what the pt can read at a distance of 20 feet, the NL population read at 100 feet
What can impaired visual acuity imply?
How would you distinguish between a correctable problem vs an more serious issue?
Abnormal acuity could be due to an ocular problem (when a patient needs glasses) or a lesion of the optic nerve or macula.
If acuity improves when looking through a pinhole, it is suggestive of an ocular problem; when it does not improve when looking through a pin hole or corrective lenses, it is suggestive of an optic nerve or macular issue
Visual Field Exam:
What is being tested?
How is it tested?
Mainly examines peripheral vision
Perimetry - quantitative method of testinv visual field, with dots on a computer screen
Beside, w/physician flickers fingers on the peripheral fields of the physician and patient
Where is the normal blind spot of a person located?
Everyone normally has a physiological “blind spot” in the temporal visual field of each eye, since the optic disc (optic nerve head) in the nasal retina is devoid of rods and cones.
What is papilledema?
Increased intracranial pressure causes the optic nerve to appear swollen on opthalamoscopic examination.
The blind spot of an eye abnormally enlarged in size in the presence of papilledema
What are scotomas?
What causes scomatas (2):
what are 3 underlying disease states associated with sarcomatas?
pathological, abnormal blind spots elsewhere in the visual field of one eye, where vision is lost or decreased.
Due to lesions in the retina (infections, inflammation, macular degen or rentinal detachments) or optic nerve (demyelination or ischemia)
associated with glaucoma or retinal degenerative disease
or psychiatric if the visual field is “tunneled” versus “constricted”
What is hemianopsia?
visual loss/impairment in half (either nasal half or temporal half) of the visual field of each eye
Describe what type of deficit is a homonymous hemianopsia?
It is caused by _____ (3).
How is the visual field impaired?
deficit of the nasal half of one eye and the temporal half of the other
Caused by: lesion in the contralateral optic tract OR the contralateral inferior (temporal lobe) and superior (parietal lobe) optic radiations or the contralateral occipital lobe.
Left Side: affect the nasal half of the right eye and temporal half of the left
Right Side: affect the nasal half of the left and temporal half of the right eye
When would you see macular sparing?
Macular sparing = preservation of central vision
Because of extensive macular represenation in the occipital visual cortex, smaller occipiatal lesions may spare macular function
Describe what a quadrantic homonymous deficit (homonymous quadrantanopsia),
visual deficit:
cause:
A smaller lesion affecting only the ….
inferior optic radiations @ temporal lobe / Meyer’s loop– > superior visual field deficit on the contralateral side
OR
superior optic radiations @parietal lobe –> inferior visual field deficity on the contralateral side
Heteronymous hemianopsia
Visual deficity involving the nasal halves of both eyes OR the temporal halves of both eyes
lesions affecting the optic chiasm at the midline would interrupt the decussating fibers from both nasal retinae –> bilateral temporal visual field losses
Optic nerve lesions produce ______
Optic chiasm lesions produce _______
Optic tract or optic radiations or occipital visual cortex lesions produce ___________
Optic nerve –> scotomas or monocular blindness
Optic Chiasm –> heteronymous visual field defects
Optic tract/optic radiation/occipital visual cortex –> homonymous visual field defects
What are acute unilateral optic nerve lesions usually due to in… young adults
older adults
In young adults usually due to demyelination (MS)
in older adults usually due to ischemia
Optic Neuritis:
What type of vision changes occur?
How do the pupils react?
How will the optic disc appear on opthalmoscope exam?
Will someone recover from this?
= inflammation of the optic nerve, usually due to lesions in the optic nerve or optic chiasm (not w/visual pathway lesions posterior to lateral geniculate body)
Vision: sudden blindness of part (scotoma) OR all of one eye; can feel achy or tender w/eye movement
Pupils: in affected eye, pupils constrict poorly or not at all; unaffected eye constrict normal to light
Optic Disc: affected disc appears swollen with indistinct, blurry margins (optic disc can appear normal if inflammation is deepr/more posterior)
Recovery? weeks –> months complete or partial recovery (partial recovery, possibly with relative afferent pupillary defect) - could lead to optic atropy (white/pale disc, with sharp edges)
Likely dx if BOTH eyes appear swollen and indistic?
Papilledema
(rare for acute optic neuritis to occur in both eyes simultaenousy)
Papilledema:
Cause:
Etiologies (4):
Opthalmascope findnigs (2):
Sx:
= optic disc swelling
due to increased intracranial pressure, usually affecting both optic discs after a period of several hours
Etiologies: extensive brain tumor or intracranial mass, meningoencephalitis or pseudotumor cerebri
Findings: flame hemorrhages, disappearance of blood vessels
Sx: H/A, N/V, impaired consciousness from the elevated ICP
What is a common lesion affecting the optic chiasm?
Which fibers are the first to be affected?
SX:
a pituitary tumor arising from the stella turcica, could exert pressure on the center of the chiasm from below
The decussating, infrerior, nasal rentinal fibers would be the first to be affected –> deficit in the superior temporal quadrants
Total lesion of the center of the optic chiasm –> bitemporal heteronymous hemianopia
SX: pituitary tumor itself would likely also cause endocrines signs and symptoms
Optic readiation lesions:
common causes (2)
a hit to the inferior optic radations –>
Tumors or ischemia can lead to lesions in the optic radiations
A lesion to Meyer’s loop (inferior optic radiations bent anterior in the temporal lobe) –> contralateral superior homonymous quadrantanopsia (“pie in the sky”)
Cortical blindness is…
common causes (2)
Pulpillary light reflex is _____
The optic disc appears ____ since the retinal ganglion cells are (yes/no) invovled
= severe visual loss from bilateral occipital lobe lesions
due to: stroke syndrome from thrombosis* of the distal basilar artery or *emboli down its posterior cerebral artery branches
although the patient is unable to see, the pupillary light reflex is INTACT and the optic discs appear NORMAL since the retinal ganglion cells are NOT invovled
Conductive deafness is caused by ________ of sound stimuli, such as water or wax plugging up the external ear canal, fusion or disruption of the bony ossicles
In an audiogram, ____ (low/high) is typical of conductive deafness
caused by IMPAIRED AIR CONDUCTION
It is a problem BEFORE the hair cell recetors
LOW-TONE hearing loss is typical of conductive deafness
Nerve (sensorineural) deafness is caused by damage or impairment of the ______ or _______
In an audiogram, ____ (low/high) tone hearing loss is indicative of nerve/sensorineural deafness
damage or impairment of the hair cell receptors or auditory nerve
caused from drug toxicity or persistent exposure to loud noise
High-tone hearling loss occurs with nerve/sensorineural deafness
Severe or complete unilateral nerve deafness is usually due to cranial nerve ____ lesions;
ischemia of _______ artery or trauma to _____ bone could be causitive factors
VS bilateral lesions are…
CN VIII lesions –> unilateral nerve deafness
causes: trauma* (esp petrous bone fractures), ischemia in the territory of the *anterior inferior cerebellar artery
more proximal, ascending auditory pathways are bilaterally represented
What type of test can help determine the type of deafness present (3)?
- Audiogram:
Low-tone hearing loss –> conductive deafness
High-tone hearing loss –> nerve/sensorineural deafness
-
Tuning fork (128 Hertz frequency C)
* *Weber Test* hold vibrating tuning fork at the top of the skull or middle of the forehead*
* [if lounder on one side = ipsilateral conductive deafness OR contralateral nerve defect]*
vibration heard BETTER in NL ear –> Nerve deafness
vibration heard BETTER in DEAF ear –>conductive deafness
*RINNE Test* hold vibrating tuning fork at the mastoid bone, when no longer heard, move outside the ipsilateral ear where it should still be heard normally (air conduction > bone conduction)
- if partial nerve deafness – air > bone, so still should be heard*
- if conductive deafness – air isNOT more efficient, thus not heard*
Dysfunction of the vestibular system produces what types of symptoms:
Dizziness or vertigo
What test could be used to test the vestibular system?
1. Dix-Hallpike Maneuver: positional maneuver to test for benign positional vertigo. The patient is moved rapidly from a sitting position to a recumbet, lateral, head-hanging @ 45degrees on the right or left. Vertigo and rotary nystagmus is induced towards the affected ear when down = posterior semicircular canal is “overly sensitive” to head movement - likely causing positional vertigo
In acute labyrinthitis, the labyrinth of the inner ear may be affected by a viral or inflammation –> sx such as (3)…
Do symptoms resolve?
What Rx can be given to help the symptoms (3):
acute labyrinthitis –> N/V, hearing impairment, unsteadiness of gait; nystagmus, unilateral decreased hearing and gait ataxia are found in examination
symptoms resolve within days to weeks
temporarily helped with benzodiazepine, antihistamine or antiemetic medciation
Meniere’s Disease presents as recurrent episodes of ____, _____ and ______.
The ________ labyrinthin swells and ruptures, allowing ______ rich endolympth to leak into the surrounding ______ –> disruption of the _______ required for normal hair cell function
RX (5)
reucrrent episodes of VERTIGO, DEAFNESS and TINNITUS
The MEBRANOUS labyrinth swells up and ruptures –> POTASSIUM - rich endolymph to leak into the surrouding PERILYMPH –> disruption of the IONIC GRADIENT required for normal hair cell function
sx are similar to acute labyrinthitis; recurrent meiniere’s episodes could lead to complete and permanet deafness
RX: antiemerics, antihistamines, benzodiazepine (same as acute labyrinthitis) + DIETARY salt restriction and diuretic medication may help reduce production of endolymph and lessen the risk of chronic deafness
Benign Positional Vertigo, seen commonly in ______ (young/old) patients
Due to: degenration of _____ and displaced _______ and other derbis that can lodge around the cilia of ______________, making them oversensitive to minor movements of the head.
SX:
Dx testing:
RX:
BPV is common in the ELDERLY
Due to: degenration of otoliths and displaced calcium crystals and other derbis that can lodge around the cilia of semicircular canal hair cells, making them oversensitive to minor movements of the head
SX: transiet/annoying vertigo when standing up or turning their heads
DX: Dix-hallpike maneuver
RX: dix-hallpike maneuver (try to disperse some of the debris in the semincircular canals or help patients readapt to head movements
