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)