Cranial Nerves 3 Flashcards
Where does the glossopharyngeal nerve leave the medulla?
Between olive and inferior cerebellar peduncle
What are the functions of the glossopharyngeal (CN9)?
a. Motor (originate from ambiguous nucleus)
i. Stylopharyngeus muscle (swallowing and speech)
b. Special sensory (end in solitary nucleus)
i. Taste from posterior 1/3 of tongue
ii. Visceral sensory fibres from chemo/baroreceptors in the carotid sinus
c. Somatosensory (end in spinal trigeminal nucleus)
i. From pharynx, posterior 1/3 of tongue
d. Parasympathetic (originate form inferior salivary nucleus)
i. Parotid gland (salivary)
What is the path of CN9?
Emerges from the medulla at the lateral side of the olive (between olive and inferior cerebellar peduncle) –> passes laterally in posterior cranial fossa –> enters the jugular foramen –> goes to the different muscles/glands
What does injury to CN9 manifest as?
a. Loss of taste from posterior tongue
b. Difficulty swallowing, and dry mouth
c. Diminished gag reflex
d. Decreased sensations at back of tongue, soft palate and pharynx
Where does the vagus nerve (CN10) leave the medulla?
Between olive and inferior cerebellar peduncle.
What are the key functions of the vagus nerve?
a. Motor
i. Muscles of pharynx and larynx important for swallowing and speech
b. Special sensory
i. Taste (from a few taste buds on epiglottis)
c. Sensory – pain, temperature, and touch from
i. Lower pharynx, larynx (involved in cough reflex) and oesophagus
ii. Wall of external acoustic meatus
iii. Tympanic membrane
iv. Neck and trunk
d. Parasympathetic – largest contribution to parasympathetic innervation
i. Viscera of thorax and abdomen (until the midgut)
ii. Glands associated with GIT
What is the path of the vagus nerve?
Emerges from brainstem as series of rootles –> come together to enter jugular foramen –> passes through neck in carotid sheath –> gives off branches to pharynx and larynx –> enter the thorax + abdomen
What does injury to vagus nerve look like?
a. Hoarseness or loss of voice – pharyngeal nerve, superior + recurrent laryngeal nerve
b. Impaired swallowing and GI motility – coeliac + superior mesenteric plexus
c. Diminished gag reflex
d. Uvula deviated to contralateral side
e. Abnormal heart rate – cardiac plexus
Where does CN11 (accessory nerve) originate from?
Medulla and cervical spinal cord (C1-C5) –> spinal accessory nucleus
What is the function of the accessory nerve?
Supplies motor innervation for Sternocleidomastoid and Trapezius muscles
What is the path of the accessory nerve?
Emerge as series of rootlets from upper 5 segments of spinal cord –> enter cranial cavity via foramen magnum –> leave cranial cavity through jugular foramen –> pass onto internal surface of sternocleidomastoid muscle –> pass across posterior triangle on the lateral side of the neck to supply trapezius muscle
What does injury to the accessory nerve look like?
- Difficulty turning head to opposite side (SCM)
- Drooping of shoulder on affected side;
difficulty raising arm above horizontal
(paralysis of trapezius)
Where does the hypoglossal nerve leave the medulla?
Between pyramid and olive (hypoglossal nuclei)
What is the function of the hypoglossal nerve?
Supplies muscles of the tongue (all intrinsic and extrinsic muscles of the tongue except the palatoglossus muscle which is supplied by CN X)
What is the path of the hypoglossal nerve?
Arises as vertical line of rootlets from ventral surface of medulla between pyramid and olive –> fibres unite together –> exit cranial cavity via hypoglossal canal –> nerve runs downwards posterior to the ICA, anterior to IJV –> crosses anteriorly over to lateral side of external carotid just above hyoid bone –> branches to tongue muscles
What does a lesion of CN12 look like?
- Difficulty in swallowing and speech * Deviation of the tongue to affected side
(one side damaged) - Cannot protrude (stick out) tongue
(both sides damaged) - Atrophy of tongue
