visual, auditory, and vestibular systems Flashcards
Is impaired visual acuity from a lesion of the optic nerve or macula improved by looking through a pinhole or by corrective lenses?
no
Perimetry
computer flashes dots
blind spot, when does it enlarge
optic disc in the nasal retina is devoid of rods and cones
-papilledema: increased intracranial pressure causes the optic nerve to appear swollen on ophthalmoscopic exam
Scotomas
abnormal blind spots
due to:
1.lesions in the retina (infections or inflammation, macular degeneration, or retinal detachments)
2. lesions of the optic nerve (demyelination or ischemia)
constricted fields can be caused by glaucoma or retinal degenerative disease, but as the examiner moves back the visual field should enlarge, what is it called if it doesn’t?
tunnel vision
-psych problem
Deficit: blindness in left eye
Lesion:
left optic nerve
11 00
Deficit: bitemporal heteronymous hemianopsia
inner optic chiasm
10 01
Deficit: binasal heteronymous hemianopsia
outer optic chiasm
01 10
Right homonymous hemianopsia
left optic tract
Right superior homonymous quadrantanopia
left inferior optic radiation (temporal lobe, meyer’s loop)
Right inferior homonymous quadrantanopsia
left superior optic radiation (parietal lobe)
Right homonymous hemianopsia (with macular sparing)
left occipital lobe
Does congruence increase when the lesion is more anterior or posterior
posterior
Optic nerve lesions produce what 2 deficits?
scotomas or monocular blindness
Optic chiasm lesions produce what
heteronymous visual field defects
Lesions of the optic tract or optic radiation or occipital visual cortex
homonymous visual field defects
optic neuritis
What is it?
How does it look on ophthalmoscopic exam?
Who gets it?
sudden blindness of part or all of one eye, which may feel achy or tender with eye movements
-pupils constrict poorly when shined in the bad eye or not at all but constrict normal when light is shined in the good eye
-weeks to months later the vision returns completely or partially (RAPD)
Ophthalmoscopic exam: optic disc appears swollen with indistinct blurry margins
-get it in MS
Optic atrophy
optic disc appears more white or pale with sharply defined edges
-some loss of ganglion cell axons has occurred
Are most one eye visual deficits with abnormal pupillary light reflex and swelling of the optic disc due to lesions before or posterior to the lateral geniculate body?
before usually of lesions of the optic nerve or optic chiasm
What is a common lesion affecting the optic chiasm?
pituitary tumor
- arises from sella turcica
- pressure from below
- ->superior temporal quadrants of the patient
- ->endocrine symptoms as well
What most often causes lesions in the optic radiations?
tumors or ischemic infarctions
Cortical blindness
severe visual loss from bilateral occipital lobe lesions
-usually a stroke syndrome from thrombosis of the distal basilar artery or emboli down its posterior cerebral branches
-pupillary light reflex is intact and the optic disc appears normal since the retinal ganglion cells are not involved
Conductive deafness
impaired air conduction of sound stimuli-water or wax plugging up the external ear canal or fusion or disruption of the bony ossicles
Nerve(sensorineural) deafness
damage or impairment of the hair cell receptors or auditory nerve
as from drug toxicity or persistent exposure to loud nois
low tone loss
conduction
high tone loss
sensorineural
complete unilateral nerve deafness
8th cranial nerve lesion
-since the more proximal auditory pathways are bilaterally represented
Which is normally more efficient air or bone conduction
air
Weber test
top of skull
-nerve deafness-both air and conduction impaired in bad ear so better heard in normal ear
-conduction deafness-better in bad ear because in that ear the environment noise is suppressed so bone conduction is enhanced
Rinne test
mastoid process–>outside the ipsilateral ear
- should be heard by air conduction when it stops being heard through bone conduction
- if partial nerve deafness than air conduction is better than bone but if conduction deafness the air no longer more efficient so it is not heard
ENG
electronystagmogram
used to record eye movements and nystagmus induced by currents of warm or cool air entering the external ear
-determines whether right or left vestibular system is impaired
Dix-Hallpike maneuver
head is tilted and lowered
-if this position creates rotatory nystagmus, that posterior semicircular canal is over sensitive and is likely to cause positional vertigo
What can cause sudden severe unilateral deafness?
trauma
- petrous bone fracture
- ischemia in the territory of the AICA
acute labyrinthitis
viral infection or inflammation cuasing severe vertigo with nausea and vomiting and hearing impairment and unsteadiness of gait
- nystagmus
- unilateral decreased hearing
- gait ataxia
-resolves within days to weeks
Meniere’s disease
recurrent episodes of vertigo, deafness and tinnitius
-membranous labyrinth swells and reptures allowing potassium rich endolymph to leak into surrounding perilymph, disrupting the ionic gradient required for normal hair cell function
same symptoms as acute labyrinthitis 1. nystagmus 2. unilateral decreased hearing 3. gait ataxia but can progress to permanent deafness
-dietary restriction of salt and diuretics can reduce production of endolymph and lessen risk of chronic deafness
benign positional vertigo
degeneration of otoliths and displaced calcium crystals and other debris can lodge around the cilia of the semicircular canal hair cells making them over sensitive to minute movements of the head
