Gross Anatomy of the Cranial Nerves Flashcards
What are the different sections of the course of a cranial nerve?
CNS part, intracranial part, base of skull part to exit foramen, extracranial part
Where is the intracranial part of the cranial nerve course?
Between point of connection with the CNS and their respective base of skull foraminae
What cranial nerve exits via the cribiform plate of the ethmoid bone?
CN I
Where does CN II exit the skull?
The optic canal
What cranial nerves exit via the superior orbital fissure?
CN III, IV, V1 and VI
Where do V2 and V3 exit the skull?
V2 = foramen rotundum V3 = foramen ovale
What cranial nerves exit via the internal acoustic meatus?
CN VII and VIII
What cranial nerves exit the skull through the jugular foramen?
CN IX, X and XI
Where does CN XII exit the skull through?
The hypoglossal canal
What are the sensory dermatomes of the trigeminal nerve?
CN V1 = forehead, upper eyelid, tip of nose
CN V2 = mid cheek, lower eyelid, nostril of nose
CN V3 = mid cheek, lower lip, chin
How do you test the sensory component of the trigeminal nerve?
Ask patient to close their eyes and gently brush skin in each dermatome with fine tip of cotton wool = ask patient to tell you when they feel it and compare each side
How do you test the motor component of the trigeminal nerve?
Palpate strength of contraction of masseter and temporalis by getting patient to clench teeth
Ask patient to open jaw against resistance
How do you test the motor part of CN VII?
Ask patient to frown, close eyes tightly, smile and puff out cheeks
How do you test the vagus nerve?
Ask patient to say ah = motor test, uvula should lift straight up, also tests CN V3
Ask patient to swallow small amount of water = watch larynx and for splutter
Listen to speech for hoarseness
Ask patient to cough
How is the spinal accessory nerve connected to the CNS?
Via cervical spinal nerve anterior rootlets to the spinal cord
What is the intracranial part of the spinal accessory nerve?
Ascends through the foramen magnum then travels towards jugular foramen in posterior cranial fossa
Where does the spinal accessory nerve course along the base of the skull?
Junction between the temporal and occipital bones
What is the extracranial part of the spinal accessory nerve?
Axons supply sternocleidomastoid on deep surface then continue across posterior triangle of neck deep to investing fascia and supply trapezius
Ho do you test the spinal accessory nerve?
Ask patient to shrug shoulders
Ask patient to turn head to look up towards opposite side
How do you tell the named nerves of the cervical plexus apart from the extracranial part of the spinal accessory nerve?
Named nerves also pass deep to midpoint of posterior border of sternocleidomastoid but don’t pass deep to trapezius
How does the hypoglossal nerve connect to the CNS?
Via many rootlets that attach lateral to pyramids of the medulla oblongata
What is the intracranial part of the hypoglossal nerve?
Passes anteriorly towards the hypoglossal canal in the posterior cranial fossa
Where does the hypoglossal nerve course along the base of the skull?
Along the occipital bone
What does the hypoglossal nerve supply?
Most of the muscles of the tongue, except palatoglossus
What is the extracranial part of the hypoglossal nerve?
Descends in neck lateral to carotid sheath, passes anteriorly at level of hyoid bone towards lateral aspect of tongue
How do you test the hypoglossal muscle?
Ask patient to stick tongue straight out = tongue tip should remain in midline
