CN 1,2,3,4,6 Flashcards
What cranial nerves originate on the midbrain
3,4
Cranial nerves originating on the pons
5,6,7,8
What nerves originate on the medulla
9,10,11,12
Basic function of cranial nerves:
1
2
3
Smell
Vision
Light accommodation
Basic nerve functions of CN
3
4
6
Eye movements
Basic functions of CN
5
7
Sensation of face/motor to mastication
Facial muscles/taste ant. 2/3
Basic functions of CN
8
9
Auditory/balance
Taste/gag
Basic functions of CNs
10
11
12
Voice/swallow
Shoulder shrug
Tongue movement
Where do cranial nerves 5,7,8 run together that might affect all nerves
Cerebellopontine angle
Contents of cribiform plate
Olfactory nerves
Contents of optic canal
Optic nerve
Contents of superior orbital fissure
CN 3,4, 5-1, 6
Contents of foramen rotundum
5-2
Contents of foramen ovale
5-3
Contents of internal auditory meatus
CN 7,8
Contents of jugular foramen
CN 9-11
Contents of hypoglossal foramen
CN 12
What may a patient with olfactory impairment complain of other than lack of smell
Lack of taste
Olfactory nerves penetrate _____ ____ and synapse with _____ cells in the _____ _____
Cribiform plate
Mitral
Olfactory bulbs
Olfactory tracts project mainly to the ______ of the ______ ______
Uncus of the temporal lobes
Olfaction is the only sensation not directly processed where?
Thalia is
What pathologies affect CN1?
- Frontal lobe tumor
- Increased intracranial pressure
- Fractures of the cribiform plate
- minor trauma to the head
Olfactory deficits can be divided into what two catetgories
Conductive and sensorineural
Conductive deficit
Process interfering with the ability of odorants to contact olfactory epithelium
Aka something stopping air from getting to receptor
Sensorineural deficits
And examples
Dysfunction of receptors or central connections
Ex: TBI, cribiform plate tumor/fracture, brain tumor
Important questions to ask patient with smell/taste disturbance
- head injury?
- smoker?
- recent URTI?
- nutrition
- exposure to toxins, medications, drugs
What nutritional deficiencies are linked to lack of smell?
Vitamin A, B6, B12
Examination of CN1
- Observe external nose
- Observe internal nasal passage (head tilt back)
- Patency bilaterally
- Close one nostril and test smell
Anosmia
Loss of smell
Ex: Alzheimer’s, Parkinson’s, Lewis body dementia
Hyposmia
Decreased smell
Hyperosmia
Increased smell
Ex: pregnant, migraines, substance abuse, deaf/blind people
Presbyosmia
Decreased smell due to aging
Parosmia
Perversion or distortion of smell
Ex: head trauma, psychiatric disease
Cacosmia
Abnormally and inappropriately disagreeable smell
Percent population that have impaired olfaction at the following ages:
- under 65
- 65-80
- 80+
- 2%
- 50%
- 75%
Why does olfaction decrease as we age?
- ossification of cribiform plate foramina
- neurogegenerative diseases
- repeated insults (lose proper structure/function)
Causes of impaired smell
- URTI
- nasal/sinus disease
- normal aging
- blocked nasal passage
- toxic chemicals/smoking
- Vitamina A, B6,12, zinc
- neurodegenerative disorders (Alzheimer’s/Parkinson’s)
- frontal lobe tumors
Foster-Kennedy syndrome
Large tumor in orbitofrontal region
Ex: olfactory groove meningioma
- Anosmia
- Unilateral ipsilateral optic atrophy
- contralateral papilledema (swelling of optic disc)
What would the findings be in Foster-Kennedy syndrome if a tumor was found in the orbitofrontal region on the RIGHT side
- anosmia
- right sided optic atrophy
- left sided papilledema
What is the most likely cause of of loss of smell with a patient?
A. Trauma
B. Concussion
C. Viral infection
D. Frontal lobe tumor
C. Viral infection
What is the function and structure of CN 2?
Detect and interpret light stimuli and strains it impulses that mediate accommodation and reflex responses
What are the sensory receptors for vision
Photoreceptors
Rods
Night vision
Low acuity
Peripheral vision
NO color
Cones
Day vision
Higher acuity
Central vision
Color vision
What photoreceptor is most numerous?
Rods
Where are cones found?>
Macula
CN two information is received by _______ on retina and synapse with ______ cells which synapse with _____ cells.
Photoreceptors
Bipolar
Ganglion
Axons from ganglion cells form optic ____ and _____ and synapse where?
Nerves and tracts
Lateral geniculate nucleus of the thalamus
After optic tracts synapse in the lateral geniculate nucleus of the thalamus they _____ to where?
Ascend
Visual cortex in geniculocalcarine tract
Lesion in the optic nerve causes what
Blindness in ipsilateral eye
Lesion in optic chiasm is known as what and causes what
Heteronymous bitemporal hemianopia
Loss of temporal visual fields
Lesion in optic tract is known as what and causes what
Homonymous contralateral hemianopia
Loss of contralateral 1/2 visual field in each eye
Heteronymous bitemporal hemianopia
Optic chiasm lesion
Homonymous contralateral hemianopia
Lesion in the optic tract
Lesion in geniculocalcarine tract is known as what and causes what
Homonymous contralateral hemianopia
Loss of contralateral 1/2 of visual field but SPARES MACULA
Homonymous contralateral hemianopia with macular sparing
Geniculocalcarine tract lesion
Exam process for CN 2
- observation of eye
- Acuity
- Visual field test
- Pupillary light reflex
- Swinging flash light test
- Ophthalmoscopic exam
Visual acuity test
Measurement of central vision
Can use newspaper at 14 inches. Equivalent to 20/30
Gross visual field test/peripheral vision/confrontation normals
50-superior
60-nasal
70-inferior
90-lateral
What does pupillary light reflex test
CN2/3
Tests for response to light both directly and indirectly
During pupillary light reflex test on the right eye the response showed pupil constricted from 4 to 3 mm. The indirect response was also 4 to 3mm. When performating the exam on the left eye the direct response was 4 to 1mm and the indirect response was 4 to 1mm. What is most likely the diagnosis?
R2: x
L2: good
R3: good
L3: good
CN 2 lesion on the right
On the right, the direct response was 4 to 3mm. The indirect response was 4 to 1mm. On the left eye, direct response was 4 to 1mm and the indirect was 4 to 3mm. what is the likely issue?
R2: good
L2: good
R3: x
L3: good
Lesion of cranial nerve 3 on the right
What does an abnormal swinging flashlight test indicate?
Afferent pupillary defect on CN2 on the side that illumination caused dilation
What would the finding be if the swinging flashlight test was abnormal
Both eyes would dilate
If in the swinging flashlight test when the light is shown in the patients left eye, both eyes dilate?
Afferent pupillary defect of CN2 on left
If there was an afferent pupillary defect on CN2 on the LEFT what would occur when light shown in right eye? Left eye?
Right: both pupils constrict
Left: both dilate
What is Marcus-Gunn phenomenon?
Pupils dilate in response to light when afferent pupillary defect of CN 2 present
Seen with optic neuritis
What diseases is Marcus-Gunn phenomenon found
Optic neuritis
Optic/retrobulbar neuritis
Inflammation of optic nerve
- rapid vision loss/scotoma (patch of loss)
- pain
What may optic neuritis be indicative of
MS
What may cause optic neuritis
MS
Infection
Autoimmune
Papilledema aka?
Chocked disc
Findings in papilledema
Increased intracranial pressure causes disc swelling
-usually bilateral, preservation of vision
What causes increased ICP that may lead to papilledema
HTN
Meningitis
Head trauma
S/S of ICP
headache
Vision issues
Nausea/vomiting
Exception to papilledema not being bilateral
Foster-Kennedy
Papilledema contralateral
Optic atrophy
Deterioration of optic nerve
What visual change occurs with optic atrophy
Decreased acuity
What color change occurs with optic atrophy
Light pink to white/grey
When may optic atrophy be seen?
Sign of more serious condition like glaucoma/stroke
Tay-Sachs AKA
Amaurotic familial idiocy
Amaurotic familial idiocy aka Tay-Sachs disease
Inherited neurodegenerate disorder causing excess gangliosides in brain/nerves
S/S of amaurotic familial idiocy aka Tay-Sachs
- decreased development, motor skills, mental functions
- blind, deaf, mentally restarted, and non-responsive to environment
- DARK CHERRY red spot in middle layer of eyes
- usually die by 5
Argyle Robertson pupil
Bilateral small pupils
-react only to accommodation
What is argyll-Robertson pupil associated with
Neurosyphillis (tabes dorsalis)
Diabetes
MS
Stroke
Holmes-adie syndrome
-one pupil larger than the other and constricts slowly to light
DTR in Holmes-adie syndrome
Absences of DTR
Extraocular muscles work in pairs that are _____?
Yoked
Cranial 3 arises from _____ ____ _____ in _____ and conveys ____ _____ to _____ muscles and ______ fibers to _____ and _____ _____
Oculomotor nuclear complex
Motor fibers to extraocular muscles
Parasympathetic fibers to pupil and ciliary body
CN 3 has motor fibers to? And parasympathetic fibers to?
Extraocular muscles
Pupil and ciliary body
CN 3 has two divisions. Superior supplying what?
Inferior supplying what?
Superior: levator palpebrae superioris
Inferior: medial and inferior recti
Inferior oblique and pupil
Action and nerve of inferior recti
CN 3
Eye down and out
Action and nerve of inferior oblique
Up and in, CN3
CN 4 arises from _____ _____ in ______ and is the only CN to exit the brain stem _______
Trochlear nucleus in midbrain
Posteriorly
CN 4 supply
Superior oblique
What structure do CN 3,4,6 all run through?
Cavernous sinus
What may occur in the cavernous sinus that would affect CN 3,4,6
Pituitary tumor
Aneurism
Extensive fiber tract running midline in the dorsal tegmentum of brainstem and extends to upper thoracic spinal cord
Medial longitudinal fasculus
Primary function of MLF
Coordinate lateral gaze by connecting nuclei of CN 3,4,6
Allows eyes to move synchronously
Lesions here may have internuclear ophthalmoplegia
MLF
Findings in patient with MLF lesion
- issues with horizontal eye movements—may describe as DOUBLE VISION
- MC complaint is trouble looking inward (reading)
What may cause a lesion in the MLF?
Older-Stroke (unilateral)
Younger-MS (bilateral)
Exotropia
Outward/lateral deviation
Heterotropia AKA ______? And meaning
Strabismus
Deviation of bilateral eye alignment
Esotropia
Inward and medial deviation
Hypertropia
Upward deviation
Hypotropia
Downward deviation
