Cranial Nerves Flashcards
Name the 3 different types of fossa in the skull
Anterior Cranial Fossa, Middle Cranial Fossa and Posterior Cranial Fossa
What symptom might you have if the Foramen Rotundum has been compressed?
Damage to Cranial Nerve Vb (Maxillary sinus)
What symptom might you have if the Optic Canal has been compressed?
Damage to Cranial Nerve II (eyesight problems)
Which cranial fossa is the cribiform plate (CNI) located in?
Anterior Cranial Fossa
An acoustic neuroma compresses which cranial nerve and what are the symptoms?
The Vestibulococchlear nerve (CN VIII). The symptoms are hearing loss and imbalance.
A pituitary adenoma compresses which cranial nerve?
The optic nerve (CNII)
Cranial nerve I (olfactory nerve), what does it do?, where does it travel and why does it work?
What?
Sensory
Where?
Olfactory mucosa through cribriform plate to olfactory tract
Why?
Sense of smell
What is anosmia and what is is caused by?
Loss of smell - caused by severence of CNI, viral infection, Parkinson’s (early sign), Alzheimer’s (early sign)
What can cause unilateral anosmia?
Meningioma or anterior cranial fossa trauma
What is Phantosmia and Cacosmia?
Phantosmia - smell things that aren’t there.
Cacosmia - smell unpleasant things
Cranial nerve II (optic nerve), what does it do?, where does it travel and why does it work?
What?
Sensory
Where?
From Retina Optic tract Optic canal Lateral Geniculate Nucleus of Thalamus
Primary visual cortex (Occipital Lobe)
Why?
Sight!
Clinically, how can you test cranial nerve II (the optic nerve)?
Via examination of Visual Acuity (reading letters on chart), visual fields, pupillary light reflex, accommodation (focusing) and fundoscopy
Cranial nerve II passes from the retina through the optic canal of which bone?
Sphenoid bone
Fill in the gaps for the optic tract below:
1. Shine light in ___ eye –> Some retinal cells send afferent information to __________ (PTN) in the midbrain
2. __________ (PTN) are linked to each other by the __________ (PC) and linked to both
___________ (EWN) by interneurons (_____ distribution)
3. Pre- ganglionic __________ fibres enter the oculomotor nerve, synapse in _________ (CG)
4. Post- ganglionic __________ fibres in short ciliary nerves enter iris, control sphincter ______
- Shine light in one eye –> Some retinal cells send afferent information to PRE-TECTAL NUCLEUS (PTN) in the midbrain
- PRE-TECTAL NUCLEI (PTN) are linked to each other by the POSTERIOR COMMISURE (PC) and linked to both
EDINGER-WESTPHAL NUCLEI by interneurons (bilateral distribution) - Pre- ganglionic parasympathetic fibres enter the oculomotor nerve, synapse in ciliary ganglion
- Post- ganglionic parasympathetic fibres in short ciliary nerves enter iris, control sphincter pupillae
What is cosensual light reflex?
Shining light in one eye should make BOTH pupils contract
Cranial nerve III (oculomotor nerve), what does it do?, where does it travel and why does it work?
What?
Motor and Parasympathetic
Where? Oculomotor nucleus (midbrain) Cavernous Sinus Superior Orbital Fissure 4/6 extraocular eyeball muscles, levator palpebrae superioris (eyelid muscle), sphincter pupillae (to constrict pupil), and ciliary muscle of the eye (lens accommodation)
Why?
Move eyeball, move eyelid, allow you to see close up, and constrict your pupils
What structure sits in the sella turcica?
Pituitary gland
What is the Cavernous Sinus and what artery and FIVE cranial nerves pass through it?
The cavernous sinus is a venous sinus (2 pockets of venous blood) on either side of the sella turcica.
The Internal Carotid Artery, Oculomotor (III), Trochlear (IV), Opthalmic (Va), Maxillary (Vb) and Abducens (VI) nerves pass through it
Fill in the gaps:
As structures pass through this venous sinus, they can be ________
They may also be affected by a _______ infection tracking into ____
Infection can cause Cavernous Sinus _________ (blood clot formed in sinus in an attempt to stop infection spread). This eventually drains into the _______
As structures pass through this venous sinus, they can be compressed
They may also be affected by a bacterial infection tracking into sinus
Infection can cause Cavernous Sinus Thrombosis (blood clot formed in sinus in an attempt to stop infection spread). This eventually drains into the Internal jugular vein
Where does the oculomotor nerve originate?
Originates in the midbrain, near to it’s parasympathetic nuclei (Edinger-Westphal)
Name the 4 muscles that move the eye, which the oculomotor nerve (CNIII) provides motor supply for?
Superior, inferior & medial Recti; Inferior oblique
Name the muscle that opens the eye, which the oculomotor nerve (CNIII) provides motor supply for?
Levator Palpebrae Superioris
Name 2 muscles which the oculomotor nerve (CNIII) provides motor supply for?
Sphincter Pupillae and the Ciliary Body
What is Exotropia and what can cause it?
When both the eyes are drawn down and out, due to lesions in CNIII
Cranial nerve IV (trochlear nerve), what does it do?, where does it travel and why does it work?
What?
Motor
Where?
Trochlear nucleus (lower midbrain) Cavernous Sinus Superior Orbital Fissure
1 extraocular eyeball muscle (Superior Oblique)
Why? Move eyeball (depression)
Which cranial nerve is the ONLY one to emerge from the dorsal side of the brainstem AND to decussate before it even emerges from the brainstem!
Cranial nerve IV (trochlear nerve)
Cranial nerve VI (abducens nerve), what does it do?, where does it travel and why does it work?
What?
Motor
Where?
Abducens nucleus (lower pons) Cavernous Sinus Superior Orbital Fissure
1 extraocular eyeball muscle (Lateral Rectus)
Why? Move eyeball (laterally) (AB-ducts your eye)
Where does the abducens nerve (CNVI) emerge from and what does it pass along to get to the superior orbital fissure?
CN VI emerges from the pontomedullary junction, passes along base of skull, turns up into the cavernous sinus (next to ICA), then through the superior orbital fissure
Which muscle does the abducens nerve provide motor supply for?
Lateral Rectus
What are the symptoms of a lesion in the abducens nerve?
No lateral movement of the eye, eye rests in adducted position = convergent squint. Horizontal diplopia
Damage to which cranial nerves can lead to a changed resting position of the eye?
CN III, IV and VI all move the eye via the extra-ocular muscles
Cranial nerve V (trigeminal nerve), what does it do?, where does it travel? and why does it work?
What?
Sensory & Motor
Where?
Trigeminal sensory nucleus (spans entire brainstem) + Trigeminal motor nucleus (Pons) Trigeminal Ganglion CN Va and Vb through Cavernous Sinus
Superior Orbital Fissure (CN Va), Foramen Rotundum (CN Vb), Foramen Ovale (CN Vc)
Facial Sensation (including cornea, anterior 2/3rds tongue, teeth), Muscles of Mastication
Why?
Sensory to the Face & Chewing!
Name the holes through which branches of the trigeminal nerve pass through.
Superior Orbital Fissure CN Va - Opthalmic
Foramen Rotundum CN Vb - Maxillary
Foramen Ovale CN Vc - Mandibular
What region of the face does the trigeminal nerve not innervate?
The angle of the mandible
How can you test the motor functions of the trigeminal nerve?
Bite down on tongue depressors look at tooth mark impression (Is it even?)
Clench teeth – Feel if masseter & temporalis contract
Jaw jerk exaggerated in UMN lesions
Open mandible - deviates toward weak side due to opening action of medial pterygoid muscle
Where does the motor nerve component of the trigeminal nerve from?
Comes from a small motor only nucleus in the Pons
These fibres exit next to the sensory trigeminal nerve fibres from the lateral pons, and accompany the Mandibular division to muscles of mastication
Cranial nerve VII (Facial nerve), what does it do?, where does it travel? and why does it work?
What?
Motor, Special Sense and Parasympathetic
Where?
Facial nucleus & Superior Salivatory nucleus (Pons) Internal Acoustic Meatus Facial canal Stylomastoid Foramen Muscles of Facial Expression (5 branches), Salivary + Lacrimal Glands and TASTE to the Anterior 2/3rds of Tongue
Why?
Facial expression, Taste & Secretomotor (saliva)
The facial nerve, enters the parotid gland, forms a plexus and gives off 5 main branches. Name these branches.
Temporal, zygomatic, buccal, marginal mandibular and cervical
Motor fibres to the FACE, travel in what tract?
Corticobulbar tract
Which halves of the face receive bilateral and contralateral innervation?
Upper half of face - bilateral innervation (both sides of cortex)
Lower half of face - contralateral innervation (opposite side of cortex)
What type of paralysis does a lower motor neuron (LMN) lesion in the facial nerve cause? E.g. Bell’s Palsy
Causes full ipsilateral palsy - complete paralysis
What type of paralysis does a upper motor neuron (UMN) lesion in the facial nerve cause? E.g. Stroke
Causes a lower facial paralysis (spares forehead)
Cranial nerve VIII (Vestibulocochlear nerve), what does it do?, where does it travel? and why does it work?
What?
Special Sense
Where?
Cochlear and Vestibular nucleus (pons) Internal Acoustic Meatus Cochlea and Vestibular Apparatus
Why?
Hearing and Balance
Which hole does the Vestibulocochlear nerve pass through?
Through Internal Acoustic Meatus into petrous portion of Temporal Bone, located in the posterior cranial fossa
How can you test the functions of CN VIII?
Balance - Hallpike Manoeuvre
Hearing - Rinne and Weber
Cranial nerve IX (Glossopharyngeal nerve), what does it do?, where does it travel? and why does it work?
What?
Motor, Sensory, Parasympathetic, Special Sense, Visceral Afferent
Where?
Inferior salivatory; nucleus ambiguus; nucleus solitarius (Medulla) Jugular Foramen
Pharynx, Parotid Gland, Taste to Posterior 1/3rd Tongue, Chemo/Baroreceptors
Why?
Motor: Stylopharyngeus muscle
Sensation: Pharynx, Chemo/Baroreceptors from Carotid Body & Sinus
Special Sense: Taste to Posterior 1/3rd Tongue
Parasympathetic: Parotid Gland
What does the glossopharyngeal nerve provide special sense to?
Taste to posterior 1/3rd of tongue
What is the glossopharyngeal nerve a sensory component of?
Gag reflex
Cranial nerve X (Vagus nerve), what does it do?, where does it travel? and why does it work?
What?
Motor, Sensory, Parasympathetic, Special Sense, Visceral Afferent
Where?
Dorsal motor; nucleus ambiguus; nucleus solitarius (Medulla) Jugular Foramen
Muscles of Palate, Pharynx & Larynx, Sensory to Laryngopharynx and Larynx,
Taste to Posterior 1/3rd Tongue (dual coverage here with CN IX)
Why?
Motor: Muscles of Palate, Pharynx & Larynx
Sensory: Laryngopharynx, Ear
Parasympathetic: Heart, Lungs, GI tract
(Swallowing, Vocalisation, Taste, Autonomics)
What cranial nerve supplies motor to the pharyngeal constrictors, palatopharyngeus, salpingopharyngeus, palatoglossus, levator veli palatini?
Vagus nerve (CN X)
What cranial nerve supplies motor to the stylopharyngeus muscle?
Glossopharyngeal nerve( CN IX)
What cranial nerve supplies motor to all the intrinsic muscles of larynx, cricothyroid & upper oesophagus?
Vagus nerve (CN X)
Where do the left and right recurrent laryngeal nerves recur under?
Left - aorta
Right - right subclavian artery
What does the GAG reflex test? (name cranial nerves)
The CN IX (Glossopharyngeal) (SENSORY portion)
&
CN X (Vagus) (MOTOR portion)
If a patient has sensation of the GAG reflex but unilateral/no contraction, what does this represent?
This shows that there is motor loss and the patient has a CN X lesion
If a patient has NO gag reflex when touching side with sensory loss, full gag when touching innervated side, what does this represent?
This shows that there is sensory loss and the patient has a CN IX lesion
Cranial nerve XI (accessory nerve), what does it do?, where does it travel? and why does it work?
What?
Motor
Where?
Arises from Nucleus in cervical spinal cord Enters cranium via Foramen Magnum then Exits cranium via Jugular Foramen Sternocleidomastoid and Trapezius
Why?
Sternocleidomastoid & Trapezius Muscles
(Moves Head and Shoulders)
What cranial nerve enters into the skull via Foramen Magnum, then OUT through Jugular Foramen?
Accessory nerve (CN XI)
How can you test for the function of CN XI on patients?
To test CN XI (Spinal Part):
Shrug shoulders
Axial rotation of neck & feel SCM
SCM weakness can sometimes lead to head turned to weak side at rest
Cranial nerve XII (hypoglossal nerve), what does it do?, where does it travel? and why does it work?
What?
Motor
Where? Hypoglossal nucleus (Medulla) Hypoglossal canal Tongue muscles (ALL except Palatoglossus – this is CN X)
Why?
Tongue Movement
The hypoglossal nerve supplies all tongue muscles, except the ______, supplied by CN ____?
Palatoglossus - CN X
Which fossa is the hypoglossal canal located in?
Posterior cranial fossa
How can you test for the function of CN XII on patients?
Ask them to protrude their tongue, if lesioned it will deviate TOWARDS weak side. So if left side has a lesion, it will deviate towards the left side.
