PDF - CN / Reflexes Flashcards
Which is CN I?
Olfactory
Which is CN II?
Optic
Which is CN III?
Occular Motor
Which is CN IV?
Trochlear
Which is CN V?
Trigeminal
Which is CN VI?
Abducens
Which is CN VII?
Facial
Which is CN VIII?
Vestibulocochlear
Which is CN IX?
Glossopharyngeal
Which is CN X?
Vagus
Which is CN XI?
Spinal Accessory
Which is CN XII?
Hypoglossal
Which is the olfactory Nerve?
I
Most common cause impaired swallowing?
Mucosal swelling / inflammation during sinusitis or an
URI
Cerebral causes loss of smell?
- Trauma: olfactory nerve branches sheared where they pass through the cribriform plate
- Tumor - near olfactory lobe at the skull base (meningioma)
Which is the optic nerve?
II
Which is the oculomotor nerve?
III
Role of Superior and Inferior Obliques?
Superior oblique: depresses and abducts eye
Inferior oblique: elevates and abducts eye
What innervates the lateral rectus?
CN VI
What innervates Superior Oblique?
CN IV
What may be weak if elevation of Eye is incomplete?
She superior rectus or inferior oblique (or both)
- When eye adducted, weakness of elevation mainly due to the inferior oblique
- When teye abducted, weakness of elevation mainly due to the superior rectus
* **Same true with inferior rectus and oblique
Presentation complete CNII lesion?
- Ptosis (paralysis levator palpebrae)
- Impacted eye ABducted (Unopposed LR)
- Pupil large and unreactive
Types of lesions causing nystagmus?
- Vestibular system
- Brain stem
- Cerebellum
Difference between drug induced nystagmus and pathological?
Drug: symmetrically seen in all directions
Path: Only seen with certain movements
Most common cause MLF (INO Lesions)?
Young: multiple sclerosis
Older: ischemic infarction
Presentation INO?
Eyes can accommodate, but when move to one vision field, the contralateral eye cannot ADduct
What is happening in INO
- Lack of communication such that when CN VI nucleus activates ipsilateral lateral rectus, contralateral CN III nucleus does not stimulate medial rectus to fire.
- Abducting eye gets nystagmus (CN VI overfires to stimulate CN III). Convergence normal.
What does MLF do?
Communicates between nuclei of CNIII and CNVI
What is normal pupillary light response?
Direct Response: shining light into one eye, causing that
pupil to constrict
Consensual: Pupil of other eye also constricts
Signalling in pupillary light reflex?
- Light in either retina sends signal via CN II to pretectal nuclei in midbrain
- Pretectal activates bilateral Edinger-Westphal nucleus; pupils contract bilaterally
How does L. CN II lesion impact pupillary light reflex?
- L. optic nerve lesion impairs afferent part of consensual reflex = neither pupil constricts when light shone in left eye
- Both pupils constrict when light shone into Right eye
How does a right CN III lesion present?
- Interrupts efferent part of consensual reflex, so the enlarged right pupil never constricts when light is shone in either eye
- Left pupil constricts with light shone in either eye
What is a RAPD?
“Relative afferent pupillary defect”
- May occur from a partial optic nerve or retinal lesion
1. Both pupils initially constrict to light
2. After moving light from normal to abnormal eye, pupillary dilatation occurs because of relatively reduced afferent input at affected eye
What is the near reflex?
Occurs when viewing a nearby object and normally consists of:
- Pupillary constriction
- Lens accommodation (“thickening”)
- Convergence of eyes
What is Light / Near dissociation? Classic Cause?
Pupils constrict during near reflex, but not to a light
1. Argyll Robertson pupils in neurosyphilis
2. Dorsal midbrain (Parinaud’s) syndrome: pineal
tumor compressing dorsal midbrain
What is horner syndrome?
Lesion disrupting oculosSYMPathetic pathway:
- Miosis: constricted pupil which dilating poorly in dark
- Anhidrosis: decreased sweating in ipsilateral face
- Ptosis: paralysis of superior tarsal muscle
Lesions causing Horner syndrome?
Lesion of spinal cord above T1:
- Pancoast tumor
- Brown-Séquard syndrome [cord hemisection]
- Late-stage syringomyelia
How does RIght CNIII Palsy present?
Right eye looking down and out
Branches of the trigeminal nerve?
- V-1: ophthalmic
- V-2: maxillary
- V-3: mandibular
Where would V1 sensory deficit present?
- Top of nose
- Forehead to temples
- Top of head
- Just under eyes and up
What is anopia? What causes?
Complete vision loss in an eye
- Caused by lesion at optic nerve
What is bilateral hemianopsia? Cause?
Loss of lateral vision fields in both eyes
- Caused by lesion of optic chiasm
- Think pituitary adenoma
What is Left homonymous hemianopia?
Loss of left visual field in both eyes
- Lesion in the optic tract
What is Left upper quadrantic anopia?
Pie in the sky lesion
- Right temporal lesion: MCA
- “Meyers Loop”
What is Left lower quadrantic anopia?
Pie on the floor lesion
- Right parietal lesion / MCA
- Dorsal optic radiation
What is central scotoma? Cause?
Cant see the visual circular field in center
- Macular degeneration
What is Left hemianopia with macular sparing?
Left vision field loss except for central macular area
- PCA infarct
What are Meyers Loop and the Dorsal optic radiation?
Meyer: inferior retina;
- Loops around inferior horn of lateral ventricle.
Dorsal optic radiation—superior retina;
- Takes shortest path via internal capsule
Presentation LMN CNVII lesion? Cause?
Severe paralysis of the entire ipsilateral half of the face
- Involves nucleus or nerve of CN VII
- Lesion at or near the stylomastoid foramen
Cause severe facial paralysis on one side?
LMN CNVII lesion
- Involves nucleus or nerve of CN VII
- Lesion at or near the stylomastoid foramen
Ipsilateral facial paralysis plus impaired taste over the anterior 2/3 of the tongue?
Indicates chorda tympani branch of CNVII also involved
Facial paralysis with hyperacusis?
CNVII lesion near stapedius muscle
- Stapedius dampens middle ear ossicle movements in presence of loud sounds, so an unpleasant sensitivity to
sound (hyperacusis) occurs
Ipsilateral facial paralysis plus impaired taste over the anterior 2/3 of the tongue, and hearing impairment / tinnitus?
CNVII lesion at CPA (internal auditory meatus)internal
- CNVIII is also involved
- Often seen in acoustic neuroma, tumor arising from VIII.
Facial paralysis with ipsilateral weakness lateral gaze?
Lesion near facial nucleus in pons
- EG: small ischemic infarction causing involvement of adjacent PPRF and CN VI
Presentation Bell’s Palsy?
Sudden onset
- Severe paralysis one side of face
- Ipsilateral hyperacusis
- Impaired taste
Rx Bell’s Palsy?
- Steroids - decrease inflammation of nerve
2. Antivirals - can be caused by HSV
Presentation facial UMN lesion in VII?
Relatively milder paralysis of only lower part contralateral face
- Sparing of the forehead
- UMNs have both ipsilateral on contralateral innervation to each side so this is case
Relatively milder facial paralysis of only lower part of face, sparing the forehead?
CNVII lesion in contralateral UMN
Difference in UMN and LMN lesion of facial nerve?
UMN lesion spares forehead as the forehead receives ipsilateral and contralateral innervation
What does decreased gag reflex when touching one side of the pharynx suggest?
Ipsilateral glossopharyngeal nerve lesion
Ask patient to say AH: drooping / sagging of palatal arch with uvula pointing toward other (normal) side?
An ipsilateral LMN lesion of CNX nerve
CN injury seen in hoarseness?
LMN lesion of CNX which innervates LMN laryngeal muscles
Decreased shrugging of shoulder along with weakness in turning head to opposite side?
CNXI lesion
Presentation of CN XII lesion?
- The genioglossus muscle, protrudes each side of
tongue forwar - LMN lesion of XII causes protruded tongue to turn toward affected side
- Overtime, affected half of tongue atrophies and fasciculates
What are crossed brain syndromes?
- Cranial nerve involvement on one side w/ adjacent fiber tract lesion
- Creates a clinical sensory or motor deficit on opposite side of the body
Which CNs arise in cerebrum?
CNI
CNII
Which CNs arise in Midbrain?
CNIII
CNIV
Which CNS arise in Pons?
CNV
CNVI
CNVII
CNVIII
Which CNS arise in Medulla?
CNIX
CNX
CNXI
CNXII
Which are the Components of brainstem?
Midbrain
Pons
Medulla
What is Weber Syndrome?
“Medial midbrain syndrome”
- Ischemic infarction of PCA
- CN III and cerebral peduncle (corticospinal/bulbar tracts)
1. Ipsilateral oculomotor nerve lesion
2. UMN weakness of contralateral face and limbs.
What is wallenberg Syndrome?
“Lateral medullary syndrome”
- Due to infarction of vertebral artery or PICA branch
1. Pain + temp impairment in ipsilateral face and
2. Pain + temp impairment in contralateral limbs and body Other symptoms may include:
3. Hoarseness
4. Vertigo
5. N/V
6. Clumsiness
7. Position sense and strength are preserved.
