Cranial nerve testing Flashcards
Anosmia
Complete loss of smell
When is anosmia concerning?
New onset, unilateral (suggests intracranial mass)
What are causes of bilateral anosmia?
Chronic rhinitis
Fracture of cribriform plate
Dysosmia/parosmia
Difficulty identifying odours
Phantosmia
Hallucination of an odour when none is present
Implies problem in the olfactory cortex
What is optic nerve responsible for?
Vision and sensory portion of pupil constriction
What are the 3 tests used to assess function of the optic nerve?
Assess visual acuity
Test peripheral vision
Check pupillary light reflex
Where does light refraction occur?
Via cornea and lens
There are no rods or cones at the optic nerve entry point. What is this point called?
Physiologic blind spot
At birth, what is the distance at which babies can have visual fixation?
8-10 inches
What is visual acuity at birth?
20/400
What is visual acuity at 6-12 mo?
20/50
At what age are babies able to track objects smoothly and symmetrically?
3-4 months
When is the lens able to change shape and focus on distant or near objects?
6 months
T/F: optic nerves and tracts are myelinating at the same time as the visual cortex is increasing in density
True!
T/F binocular use of visual pathways is activity driven and should be learned early in life
True!
T/F myelination ends in the central visual pathways at 6-12 months
False- happens until 4 years old
/F development of the visual cortex continues until you are 20
False- continues through first decade (10 years old)
When should we start visual screening for kiddos?
3 years old
T/F we use a Snellen chart to test visual acuity in kids
False- Allen eye chart
What is a good visual acuity for kids 3-5 years old?
20/40 or better
What is good visual acuity for kids 5+ years old?
20/32 or better
Amblyopia
Lazy eye
Unilateral
Leading cause of monocular vision loss
Ocular structures are normal
If a kid has anisometropia, what are they at an increased risk of getting?
Amblyopia
The dominant eye will take over and the less dominant eye will become lazy
What is anisometropia?
Unequal refractive power between the two eyes
Treatment for preventing amblyopia in a kid thwt has anisometropia?
Corrective lenses
What is tropia?
Eye deviation and poses a risk for amblyopia, especially if it constantly occurs
Where is the image created in myopia?
In front of the retina
Is the refractive power too great or too little in the lens with myopia?
To great
Is the refractive power too little or too great with hyperopia?
Too little
Where does the image come into focus in hyperopia?
Behind the retina
In axial myopia, what is the shape of the eyeball?
Longer than average, increasing risk foe degenerative changes
Axial hyperopia shape of eyeball?
Shorter than average
Define astigmatism
Abnormally shaped cornea causing unequal refraction in different meridians of the eye
What occurs with age?
A) myopia
B) presbyopia
C) hyperopia
B) presbyopia
Which aspect of the visual field is greatest?
Temporal
What constitutes legal blindness?
Total diameter of vision loss is less than or equal to 20 degrees in the BETTER eye
Which side of the brain are right visual field images processed?
Left side of the brain
What is a scotoma?
An area of depressed vision surrounded by normal vision
What is a scintillating scotoma and what is it a prodrome for?
Partial alteration in the visual fields that is a common prodrome to classic migraines (Migraines with Aura)
What would cause hemianopsia bilaterally?
Pituitary tumour damaging the optic chiasm
What would cause left homonymous hemianopsia?
Right optic tract defect
Or complete Right optic radiation defect
What would cause homonymous right superior quadrantic defect?
Partial left optic radiation lesion
What would cause COMPLETE right eye blindness?
Lesion of the optic nerve
Does crainial nerve 3 generate an afferent impulse or an efferent response?
Efferent response bilaterally!
T/F
A patient should have both a direct and consensual response as part of the normal pupillary light reflex
True
What kind of scents do we use to test OLFACTORY nerve?
Familiar, mild scents - not noxious smells
