(15) CN V, VII, IX, X, XI, XII Flashcards
at what brainstem level is the trigeminal nuclei found
mid pons
path of CN V motor fibers
**esp foramen
trigeminal nuclei → V3 → exits cranium via foramen ovale → muscles of mastication (masseter and temporalis muscles); tensor tympani (dampens sound); tensor veli palatine; mylohyoid; anterior belly of diagastric
What is the jaw jerk reflex?
tapping on masseter muscle (or temporalis????) stretches muscle spindles → signal travels via afferent fibers to mesencephalic nucleus of V → interneuron sends signal to motor neuron nucleus in motor nucleus → impule for masseter to contract
How is CN V tested?
bite down to test jaw strength (do bilaterally)
travels on floor of meckel’s cave
CN V motor fibers as V3 (mandibular branch)
UMN input to trigeminal motor nuclei is (uni or bi)
bilateral
where must a lesion be in order to cause UNIlateral weakness in jaw closure
CN V or its nuclei
CN VII motor neurons arise in ______ nucleus in the _____ level of the brain stem to innervate ______
facial nucleus at the mid pons to innv muscles of facial expression
CN VII parasympathetic fibers CN VII motor neurons arise in ______ nucleus in the _____ level of the brain stem to innervate ______
salivary nucleus at the rostral medulla to innv lacrimal and salivary glands
travels through the nervus intermedius
parasympathetic fibers on CN VII
Where does CN VII and nervus intermedius exit the brainstem
pontomedulalry junction at the cerebellopontine angle
What is the facial colliculus
the bump on the floor of the 4th ventricle caused by the fibers of the facial N looping over the abducens
CN VII exits the cranial vault via
internal auditory meatus → auditory canal where it bends ventrally to exit the skull via the stylomastoid foramen
primary parasympathetic neurons serving salivary and lacrimal glands synapse with secondary neurons in _____ nucleus
sphenopalatine and submandibular ganglion
how is CN VII tested
ask pts to wrinkle forehead, close eyes tightly, show their teeth (movements should be symmetric)
CN VII leasion will cause the eye opening to inc or dec at rest
increase
consequence of unilateral motor cortex or corticobulbar fibers (UMNs) on the muscles of facial expression
forehead will be spared but lower facial muscles will be weak on the contralateral side
consequence of unilateral LMN fiber lesion of CN VII
ipislateral weakness of forehead and lower facial muscles
CN IX motor neurons arise in ______ nucleus in the _____ level of the brain stem to innervate ______
nucleus ambiguus which is near the junction of the pons and medulla to innervate the stylopharyngeus muscles
CN IX parasympathetic pre gang neurons arise in ______ nucleus in the _____ level of the brain stem travels via ______ to _____ ganglion where it synapses with post gang fibers that will innervate _____
inferior salivary nucleus at the midline of the medulla → CN IX → lesser petrosal N → otic ganglion to innervate the parotid gland
UMN and LMN lesions to CN IX will clinically manifest as
dysphagia
How is CN IX tested?
eliciting a gag reflex (although this is sensory IX and mostly motor X, but with some IX)
CN X motor neurons arise in ______ nucleus in the _____ level of the brain stem to innervate ______
nucleus ambiguus in the lateral medulla to innv muscles of the soft palate, larynx, and pharynx
CN X parasympathetic pre gang neurons arise in ______ nucleus in the _____ level of the brain stem travels via ______ to _____ ganglion where it synapses with post gang fibers that will innervate _____
dorsal motor nucleus at the midline medulla → pre gang travel with CN X to intramural ganglia assc with heart, lung, digestive tract to innv tissues in the organs
where does CN X exit the brainstem
between the inferior olive and the inferior cerebellar peduncle
CN X exits the skull via
jugular foramen
CN X has bi or unilateral UMN innvervation
bilateral
where will a lesion be found that produces dysphagia, hoarseness, and inability to elevate the soft palate. (will these symptoms be on the ipsilateral or contralateral side)
LMN CN X with the signs on the ipsilateral side
UMN has bilateral input
CN XI has motor fibers that originate in _____ nuclei which are found…
nucleus ambiguus in the lateral medulla
spinal accessory nuclei in the intermediolateral gray matter (btwn ventral and dorsal horns) of C1-C5
**fibers from these 2 areas join together to form the spinal accessory nerve
Where do CN XI fibers exit the spinal cord and where do they go?
exit between the dorsal and ventral roots to ascend along the spinal cord enter the cranium via the foramen magnum then exit via the jusgualr foramen to innervate SCM and trapezius
*note the fibers from the ambiguus nucleus join CN XI only for a short while before joining with CN X (→ jugular foramen)
How is CN XI tested?
elevating the shoulders and turning the head
how will and LMN CN XI lesion present?
ipsilateral weakness in elevating shoulder; weakness in rotating head away from the lesion; may see atrophy of SCM and trapezius
how will and UMN CN XI lesion present?
contralateral weakness in elevating the shoulder and weakness in rotating head away from the lesion (ipsilateral SCM weakness)
CN X motor neurons arise in ______ nucleus in the _____ level of the brain stem and exit brain stem at to innervate ______
hypoglossal nucleus at the medulla
exit brainstem between the inferior olives and the pyramids (nerve found at the junction of the medulla and the spinal cord)
innervates the tongue (intrinsic and extrinsic muscles)
CN XII exits the cranium via…
hypoglossal foramen
diff in presentation of a LMN vs UMN lesion of CN XII
LMN: tongue points towards the side of the lesion
UMN: tongue points away from the side of the lesion
**this is bc the corticobulbar fibers from the motor cortex cross over to the contralateral hypoglossal nuclei
