Cranial Nerves Lecture 3 Flashcards
Olfactory (CN I)
- Function: (SVA) special sense of smell
- Location: Olfactory organ
- Tract: Cribriform plate to olfactory bulbs
Anosmia
Olfactory loss • Contralateral nostril can compensate for unilateral anosmia • Causes: Head trauma, viral infections, Intracranila lesions, nasal passage obstruction
Optic (CN II) function
(SSA) special sense of
vision
Optic (CN II) tract
• Optic nerve fibers arise from ganglion cells in retina • Exit the orbit via the optic canal into the middle cranial fossa • Most fibers terminate in lateral geniculate bodies of thalamus
what is relationship of optic chiasm to pituitary?
right next to each other. Pituitary can compress and cause lateral vision loss in both fields (bitemporal hemainopia)
what is relationship of internal carotid artery to optic chiasm
next to each other. aneurysm can compress optic chiasm
CN II testing
- light and dark (head injury
- finger counting (head injury)
- snellens test (eye chart)
- visual field test (4 quadrants)
- peripheral vision
- pupillary light reflex
- blink reflex
Oculomotor (CN III) function
• (GSE) Motor innervation to superior, medial, and inferior recti and inferior oblique and levator palpebrae superioris • (GVE) Parasympathetic innervation to pupil and ciliary muscle
Oculomotor (CN III) tract
• Leaves the midbrain • Pierces dura lateral to diaphragma sellae • Runs in lateral wall of cavernous sinus • Enters orbit via superior orbital fissure
Trochlear (CN IV) function
Motor innervation to
superior oblique
Trochlear (CN IV) tract
• Exits dorsal surface of midbrain • Pierces dura mater at the margin of the tentorium cerebelli • Run in the lateral wall of cavernous sinus • Enters the orbit via the superior orbital fissure
Abducens (CN VI) function
• (GSE) Motor innervation to the
lateral rectus
Abducens (CN VI) tract
• Emerges from brainstem between pons and medulla • Traverses the pontine cistern • Pierces dura covering the clivus • Runs in the cavernous sinus near the ICA • Enters orbit via superior orbital fissure
which 2 nerves can be compressed by aneurysm?
CN III and CN VI (between 2 arteries)
Trigeminal (CN V) function
• (SVE) Motor innervation to muscles
of mastication (pharyngeal arch 1)
• (GSA) Sensory to the face and
scalp
Trigeminal (CN V) tract
• Emerges from lateral aspect of pons
• Trigeminal ganglion located in the
trigeminal cave lateral to the
cavernous sinus
*branches to 3 different divisions
• V1 Ophthalmic: tract
Passes through the
cavernous sinus and enters the orbit
via the superior orbital fissure
v2 maxillary tract
Passes through the
cavernous sinus and exits the skull
via foramen rotundum
v3 mandibular tract
Exits the skull via the
foramen ovale