Visual, Auditory, and Vestibular System

Question 1

What is visual acuity a function of?

Answer 1

Central vision involving the macula

Question 2

What is color vision a function of?

Answer 2

Macula

Question 3

Improved acuity when looking through a pinhole suggests the problem with visual acuity is ___. If it does not improve, what should be suspected?

Answer 3

Ocular; lesion of the optic nerve or macula

Question 4

The normal blind spot abnormally enlarges in size in the presence of what pathology?

Answer 4

Papilledema

Question 5

What are scotomas?

Answer 5

Pathological, abnormal blind spots elsewhere in the visual field of one eye, where vision is lost or decreased

Question 6

Causes of scotomas?

Answer 6

Retinal lesions (infections or inflammation, macular degeneration, retinal detachment) or optic nerve lesions (demyelination or ischemia)

Question 7

Patients with constricted or contracted visual fields may have underlying ___ or a ___ disease.

Answer 7

Glaucoma; retinal degenerative

Question 8

Tunnel vision is usually due to what type of problem?

Answer 8

Psychiatric

Question 9

Describe how vision is transmitted from the outside world to the cortex.

Answer 9

Visual image in the R side of the patient’s world is detected by the L halves of each retina

Transmitted by optic nerve fibers which, beyond the optic chiasm, are continued as a pathway through the L optic tract, then the L optic radiations, ending in the L occipital visual cortex

Question 10

Presentation of post-chiasmal lesions on the left?

Answer 10

R-sided visual impairments

Question 11

A visual image in the uppermost part of the patient’s world is detected by the ___ portions of the retinae, and these fibers continue past the optic chiasm as the ___ of the temporal lobe.

Answer 11

Inferior; inferior optic radiations

Question 12

Presentation of a temporal lobe lesion involving the inferior optic radiations?

Answer 12

Contralateral deficit in the patient’s superior visual world

Question 13

Presentation of a L optic nerve lesion (excluding ocular/retinal causes)?

Answer 13

Blindness of the L eye

Question 14

Presentation of an inner optic chiasm lesion?

Answer 14

Bitemporal heteronymous hemianopsia

Question 15

Presentation of a L outer optic chiasm lesion?

Answer 15

R sided nasal heteronymous hemianopsia

Question 16

Presentation of a L inferior optic radiation lesion (temporal lobe, Meyer’s loop)?

Answer 16

R superior homonymous quadrantanopsia

Question 17

Presentation of a L superior optic radiation lesion (parietal lobe)?

Answer 17

R inferior homonymous quadrantanopsia

Question 18

Presentation of a L occipital lobe lesion?

Answer 18

R homonymous hemianopsia with macular sparing

Question 19

Congruence of visual field deficits increases when the lesion is more ___.

Answer 19

Posterior (occipital lobe, superior and inferior optic radiations)

Question 20

In summary, optic ___ lesions produce scotomas or monocular blindness. Optic ___ lesions produce heteronymous visual field defects. Lesions of the ___ or ___ or ___ cortex produce homonymous visual field defects.

Answer 20

Nerve; chiasm; tract; radiations; occipital

Question 21

Causes of acute unilateral optic nerve lesions in younger and older adults?

Answer 21

Younger - demyelination (MS, etc.)

Older - ischemia

Question 22

Presentation of optic neuritis?

Answer 22

Sudden blindness of part (scotoma) or all of one eye, which may feel achy or tender with eye movement; pupils constrict poorly or not at all with light shined into the involved eye, but constrict normally with light shined into the normal eye

Optic disc appears swollen with indistinct, blurry margins

Question 23

Weeks to months after acute optic neuritis, vision has recovered completely or partially. What residual deficits may remain?

Answer 23

Residual scotoma with or without impaired visual acuity or color vision; possible relative afferent pupillary defect

Question 24

Presentation of optic atrophy (due to loss of ganglion cell axons)?

Answer 24

Optic disc appears more white or pale with sharply defined edges

Question 25

Fundoscopic findings of papilledema?

Answer 25

Swollen and indistinct optic discs

Flame hemorrhages may be seen around the optic discs

Blood vessels passing through the optic disc may appear from the plane of focus as the rise up over the “mound” of the elevated, swollen disc

Vision is not affected initially, but may be impaired or lost if the increased ICP continues

Question 26

Describe the progression of a pituitary tumor arising from the sella turcica.

Answer 26

Initially, the decussating inferior nasal retinal fibers would be affected, creating a visual deficit in the superior temporal quadrants; total lesion will produce a bitemporal heteronymous hemianopsia

Question 27

What can cause lesions in the optic radiations?

Answer 27

Tumors or ischemic infarcts

Question 28

What causes cortical blindness?

Answer 28

Severe visual loss from bilateral occipital lobe lesions; usually a stroke syndrome from thrombosis of the distal basilar artery or emboli down its PCA branches

Note - pupillary light reflex intact, optic discs normal

Question 29

Two types of hearing impairment?

Answer 29

Conductive deafness

Nerve (sensorineural) deafness

Question 30

Cause of conductive deafness?

Answer 30

Impaired air conduction of sound stimuli, such as water or wax plugging up the external ear canal, or fusion or disruption of the bony ossicles

“Before” the hair cell receptors

Question 31

Cause of nerve (sensorineural) deafness?

Answer 31

Damage or impairment of the hair cell receptors or auditory nerve, as from drug toxicity or persistent exposure to loud noise

Question 32

Low-tone hearing loss is typical of ___ deafness, while high-tone hearing loss occurs with ___ deafness.

Answer 32

Conductive; nerve (sensorineural)

Question 33

Severe or complete unilateral nerve deafness is usually due to what lesion?

Answer 33

CN VIII (as the more proximal, ascending auditory pathways are bilaterally represented)

Question 34

Bone conduction is the means by which vibrating sounds, such as one’s own voice, are transmitted through the skull to sound receptors. Air conduction allows the detection of airborne sounds by the tympanic membrane and ossicles, which amplify the stimuli before sounds are transmitted to the cochlea. Which is more efficient normally and why?

Answer 34

Air conduction, because of the amplification system

Question 35

What is the Weber test and what is it examining?

Answer 35

Holding the vibrating tuning fork at the top of the skull or middle of the forehead

If nerve deafness has occurred in one ear, both air and bone conduction are impaired. The vibrating tuning fork is heard better in the normal ear.

If conductive deafness has occurred in one ear, the vibrating tuning fork is heard better in the affected ear, since bone conduction is enhanced.

Question 36

What is the Rinne test and what is it examining?

Answer 36

Hold the vibrating tuning fork at the mastoid bone, allowing the vibration to be heard by bone conduction. When no longer heard here, the vibrating fork is then held outside the ipsilateral ear, where it should still be normally heard, since air conduction is better than bone conduction. If partial nerve deafness is present, air conduction is still better than bone conduction. If there is conductive deafness, air conduction is no longer more efficient, so the fork is not heard once bone conduction stops.

Question 37

Dysfunction of the vestibular system typically produces what symptom?

Answer 37

Vertigo or motion-induced dizziness

Question 38

What is the Dix-Hallpike maneuver and what does it test?

Answer 38

Patient lies supine with head titled about 45 degrees below the edge of the table, turned to one side; selectively tests the posterior semicircular canal with the tilted lowered ear. If the position creates rotatory nystagmus, that canal is overly sensitive and likely the cause of positional vertigo

Question 39

Sudden severe unilateral deafness may be due to trauma particularly with ___ bone fractures, or from ischemia in what territory?

Answer 39

Petrous; AICA

Question 40

Presentation of acute labyrinthitis?

Answer 40

Viral infection or inflammation of the labyrinth of the inner ear leads to severe vertigo with N/V, hearing impairment, and unsteady gait

Nystagmus, unilaterally decreased hearing, and gait ataxia on exam

Question 41

Rx acute labyrinthitis?

Answer 41

Symptoms resolve within days to weeks, temporarily helped with benzo,s antihistamine, or antiemtitics

Question 42

Presentation of Meniere’s disease?

Answer 42

Recurrent episodes of vertigo, deafness, and tinnitus

Question 43

Cause of Meniere’s?

Answer 43

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

Question 44

Rx Meniere’s?

Answer 44

Same as acute labyrinthitis; however, repeat episodes may lead to permanent deafness. Dietary salt restriction and diuretic medications may help reduce production of endolymph and decrease the risk of deafness

Question 45

Presentation of benign positional vertigo?

Answer 45

Elderly; transient but annoying vertigo when standing or turning heads

Question 46

Cause of benign positional vertigo?

Answer 46

Degeneration of otoliths and and displaced calcium crystals can lodge around the cilia of semicircular canal hair cells, making them oversensitive to minor movements

Question 47

Rx BPV?

Answer 47

Head-turning exercises to disperse debris