Cranial Nerve Review and Palsy Flashcards
Mnemonic for CNs
Oh Oh Oh, To Touch and Feel Very Good Velvet, Such Heaven
Mnemonic for Sensory/Motor
Some Say Money Matters But My Brother Says Big Boobs Matter More
Cranial Nerves: Anatomy and Function
• Olfactory/Optic n. = don’t leave cranial vault, so sometimes not considered pure cranial nerves
o Olfactory = smell (sensory)
o Optic = see (sensory)
• Oculomotor = innervate muscles of eyeball, helps to rotate globe
• Trochlear = innervate superior oblique m.
• Trigeminal = innervates sensation of skin of face and inferior portion of turbinates and some of the tongue, involves muscles of mastication
• Abducens = innervate lateral rectus m.
• Facial = innervates muscles of facial expression and sensations of taste (tongue and parotid gland). Innervate lacrimal gland and sensation to inferior nasal cavity near turbinates
• Vestibulo-cochlear = controls hearing and balance
• Glossopharyngeal = innervates salivary gland (parotid gland) and muscles that allow us to swallow. Innervate inner portion of ear
• Vagus = sensation or coughing (along with glossopharyngeal), innervate parasympathetic—most of internal organs (heart, lungs, stomach, bowel)
• Spinal Accessory = innervate muscles that allow you raise shoulders like trapezius
• Hypoglossal = innervate tongue
Mnemonic for Eye Muscle
LR6SO4R3
CN III Palsy
- Muscles Innervated
- SX of Palsy
- Other Notable Info
Muscles Innervated
- 4 external ocular muscles (superior, inferior, medial rectus + inferior oblique muscle)
- levator palpebrae superior muscle, keeps eye open! (VS Orbicularis muscles via Facial Nerve! = keeps eyes closed)
- Pupil constrictor muscle (via parasym fibers of CN III)
Sx of Palsy
- Downward and Out Gaze.
- Ptosis (drooping of eyelid)
- Dilated Pupils
- Loss of accommodation of the lens (near vision blurred)
- Lateral strabismus
Note: Opthalmic artery runs through cavernous sinus where CN III is and if aneurysm occurs = pressure can lead to palsy.
CN IV Palsy
- Muscles Innervated
- Sx of Palsy
- Other Notable Info.
Muscles Innervated
- Superior Oblique Muscle = Downward and out gaze, pulley + INTERNAL Rotation.
Sx of Palsy
- Contralateral eye extorsion (OUTWARD rotation of superior part of the globe) = compensated via slightly downward tilt of head!
- Diplopia (torsional double vision in bilateral palsies)
- Note: Don’t always see upward and in gaze.
Note: The nerve crosses in the SUPERIOR MEDULLARY VELUM before emerging from the DORSAL surface of the brain stem = nucleus of trochlear nerve lies dorsal surface of brainstem and comes out ventrally. Only CN to do this.
CN VI
- Muscles Innervated
- Sx of Palsy
Muscles Innervated
- Lateral Rectus
Sx of Palsy
- Medial deviation/gaze or esotropia
CN VII (Part 1)
- Innervation
- Mnemonic for Branches
- Sx of Palsy
Innervation
- Superior Salivatory Nucleus = Lacrimation and Salivation
- Taste of anterior 2/3 of tongue
- Muscles of facial expression
- Sensation to inferior nasal cavity near turbinates
- Orbicularis muscle = controls closing of the eye (therefore if there is a lesion on a test, they can’t keep their eyes forcefully closed.
Mnemonic for Branches
- To = Temporal Branches
- Zanzibar = Zygomatic Branches
- By = Buccal Branches
- Motor = Marginal Mandibular Branch (with motor branch)
- Car = Cervical Branch
Note: Genu of the facial nerve lies in the pons. The other 3 components lie in the medulla
CN VII (Part II)
- Palsy = LMN vs UMN Lesion
- Specifics of motor nucleus (2 part division)
Palsy: LMN vs UMN Lesion
- LMN Lesion = Entire ipsilateral side of face becomes parazlysed, also seen in Bell’s palsy. Therefore has marked difficulty in closing the eye.
- UMN Lesion = Contralateral lower area of face (below the eye) because of BILATERAL innervation of the upper face by the two cerebral hemispheres. Therefore you won’t see difficulty in closing the eye.
Specifics of motor nucleus
- Divided into two parts: Small part that innervates the upper facial muscles and larger part that supplies the lower facial muscles
- Upper Face Muscles: Both sides of brain control it
- Lower Face Muscles: Contralateral sides of brain control it.
Bell’s Palsy
- Sx + More
Def: Lesion of Facial Nerve = facial nerve exiting meatus down the stylomastoid foramen where it goes to innervate facial musculature: here is where the lesion can cause Bell’s Palsy.
- Ipsilateral Weakness of both upper and lower facial nerves + inability to close the eye tightly (LMN Lesion)
- CHORDA TYMPANI NERVE: Lacrimation, Salivation, + taste may be impaired
Note: Return of function is often accompanied by “crocodile tears” = patient tears up on eating instead of salivating due to misguided growth of regenerating salivary and lacrimal fibers
CN XII
- Muscle Innervation
- Palsy SX
Muscle Innervation
- Ipsilateral muscle of the tongue.
Palsy Sx (LOWER motor neuron lesion)
- Atrophy/Wasting of ipsilateral side of tongue
- Tongue deviates towards side of lesion (lick the wound)
Bulbar Palsy vs Pseuodo-Bulbar Palsy
Note: Both involve medulla and pons
Bulbar Palsy - Lower Motor Neuron lesion
- CN 10, 11, and 12 are involved.
- Sx: Flaccidity, Fasciculation, Atrophy of Muscles, paralysis, and diminished reflexes = overall decrease
- Note: Jaw Jerk reflex is normal because CN 5 and 7 are not involved.
Pseudo-Bulbar Palsy - bilateral upper motor neuron lesion.
- Paralysis of swallowing and phonation.
- Pons 5 and 7 are UNIQUE to Pseudo-Bulbar Palsies which result in problems with muscles of mastication and facial expression
- Medulla (CN 10, 11, 12) = bilateral degeneration of cortical bulbar tracts which lead to spastic dysarthria and altered phonation in tone.
- Sx: Increased Reflexes and Spasticity of Muscles
