Lab 8 from Lab Manual Flashcards
Infart involving entire right medullary pyramid, the right hypoglossal nerve as it exits the medulla, the right medial leminiscus, and a small portion of the inferior olivary nucleus would cause what deficits?
Alternating hypoglossal hemiplegia.
Infarct in medullary pyramid (CST) –> Contralateral (left) hemiplegia (paralysis)
Infart in CNXII –> ipsilateral (R) tongue paralysis
Infarct in ML –> contralateral (L) sensory loss in body (not head)
Infart in lateral medulla affecting only the descending sympathetic, ascending spinothalamic fibers, and nucleus ambiguous.
Severe swallowing disorder. Infarct of nucleus ambiguus produces hemiparesis of bulbar musculature.
Incomplete Wallenberg syndrome - ipsilateral Horners syndrome (miosis, ptosis, anhidrosis) + contralateral anesthesia to pain and temperature
Glioblastoma in pons involving the descending corticospinal and corticobulbar tracts +
dense right hemiplegia + left trigeminal palsy
Thrombus at the bifurcation of his basilar artery –> complex “top of the basilar” infarct.
Complete, bilateral third nerve palsy and “blown pupils” from the unopposed sympathetic input to the iris.
Also coma because RAS was severed from cerebrum.
The oculomotor nerve contains two distinct types of efferent signals. Name them and what they do. Where does this nerve exit the brainstem?
Efferent signals: motor neuron input to the extraocular muscles (medial, inferior, and superior rectus muscles and inferior oblique) and parasympathetic input to iris and lens.
Where does this nerve exit the brainstem??!?!
Trochlear nerve function and course.
Innervates the superior oblique intrinsic eye muscle, that intorts and depresses the globe.
The lower motor neurons lie in the ventral caudal midbrain, at the level of the decussation of the superior cerebellar peduncle. It is buried in the medial longitudinal fasciculus. Its fibers then descend, move dorsally, cross at the dorsal side of the periaqueductal gray, and exit from the posterior. After that, they then move ventrally around the brainstem, eventually join up with VI and III, and exit through the superior orbital fissure.
Trochlear nucleus in the caudal midbrain.
Trochlear nerve exiting from the dorsal brainstem at the pontomesencephalic junction.
Trigeminal nerve What are its sensory divisions? Its motor functions? Mark its position on the brainstem and describe its peripheral ganglion. Name and paste its associated nuclei. Discuss the level of the brainstem and the functional aspects of each nucleus.
Ganglion lies outside the dura at the base of the brain. 3 divisions travel through three foramen: superior orbital fissure for the ophthalmic division (sensation above the midline of the eyes), the foramen rotundum for the maxillary divi- sion (sensation below the midline eye to the jaw), and the foramen ovale for the mandibular division (jaw sensation and motor function).
Pain and temperature fibers from the face descend from their entry in the pons down into the medulla and upper spinal cord, ending in the spinal trigeminal nucleus. This is true not only for trigeminal nerve fibers, but for somatic sensations traveling into the brain through other cranial nerves as well. The information crosses and ascends to join the spinothalamic fibers.
Proprioceptive information is processed in the principal trigeminal sensory nucleus, immediately lateral to the trigeminal motor nucleus. (Remember, the branchial nuclei are all lateral, but their motor fibers lie more medial than the sensory.) This information also crosses and joins the medial lemniscal fibers.
A special set of sensory fibers derived from the muscles of mastication have their dorsal root ganglion fibers in the brainstem itself, in the trigeminal mesencephalic nucleus. These are involved in the jaw jerk reflex.
Spinal trigeminal nucleus in medulla, primary trigeminal sensory nucleus in pons, mesence- phalic nucleus in upper pons, and trigeminal motor nucleus in pons.
Abducens function, course, and nucleus location.
The abducens nerve controls the lateral rectus muscle, and thus abducts the eye. It travels from the base of the pons to the eye muscles (subject to diabetic injury). Its nucleus also lies at the other end of the pons from its siblings; their connection, the medial longitudinal fasciculus, is long and also may be injured by diseases such as multiple sclerosis.
Exits at the junction of the pons and the medulla.
Abducens nucleus in lower pons.
Facial sensory function, course, and nucleus location
Somatic sensory information from the external ear travel through this nerve, but ends up in brainstem trigeminal sensory nuclei. It also contains parasympathetic fibers innervating salivary and lacrimal glands.
Facial motor and visceral sensory functions, course, and nuclei locations.
The facial nerve, from its motor nucleus in the lowest pons, controls the superficial muscles. These not only express your feelings, but control your cheeks and blinking. Taste sensation from anterior 2/3 tongue travels through the chorda tympani, through the nervous intermedius to the rostral solitary nucleus. Notice how these nuclei, like the trigem- inal, are lateral.
Facial motor nucleus in the caudal pons and the solitary nucleus in the dorsal medulla.
Vestibulocochlear function, course, nucleus.
The semicircular canals, saccule, and utricle send their circular and linear acceleration information to the vestibular nuclei (four) and the cochlea transmits its auditory signals to the cochlear nuclei (dorsal and two ventral).
Exit of the vestibular and cochlear nerves at the cerebel- lopontine angle.
Location of the cochlear nuclei and vestibular nuclear complex in the rostral medulla.
Glossopharyngeal function, course, and nucleus
Transmits taste sensation from posterior 1/3 of tongue, sends parasympathetic impulses to the parotid gland (from a salivatory nucleus), and innervates stylopharyngeal.
Special autonomic sensory from the carotid body (chemosensory) and carotid sinus (pressure). This information, along with taste from the back of the tongue, ends up in the solitary nucleus. The pharyngeal sensory fibers end up in the trigeminal sensory nuclei. The stylopharyngeal muscles are innervated by motor neurons in the nucleus ambiguus.
The sensory portion of the gag reflex derives from glossopharyngeal receptors in the mouth, while most of the motor component originates from ambiguus nucleus and travels in the vagus nerve.
Solitary nucleus and nucleus ambiguus in medulla.
The vagus nerve provides preganglionic parasympathetic motor fibers to most of the body and supplies motor control over swallowing and vocal cords. Where are the nuclei?
The parasympathetic fibers originate from the dorsal motor nucleus of the vagus while the pharyngeal muscle lower motor neurons reside in the nucleus ambiguus. The autonomic sensations, like all autonomic sensations, pass to the solitary nucleus.
Hypoglossal nerve function, course, and nucleus.
What happens if you ask a patient with a left hypoglossal nerve palsy to stick out his tongue?
The hypoglossal nerve innervates muscles in the base of the tongue. Contracting both sides causes the tongue to protrude directly out, while contracting the left side makes the tongue move right.
Should you ask a patient with a left hypoglossal nerve palsy to “stick out your tongue”, only the right side will contract, and their tongue will point left or toward the side of the lesion.
Hypoglossal nerve rootlets exiting between the inferior olive and the pyramids.
Hypoglossal nucleus in the medulla.
