Lecture 9: Brainstem & Corticobulbar Pathways Flashcards
Describe the deficits that would be seen with occlusion of the lenticulostriate arteries on the right (i.e., extremities, face, uvula, tongue, trapezius/SCM)?
- Left spastic hemiparesis of the extremities (corticospinal damage)
- Central facial paralysis on the left
- Deviation of uvula to the right on phonation
- Deviation of tongue to the left when protruded
- Effects on the trapezius and SCM are variable (ipsilateral deficits)
Which 3 CN and nuclei that are associated with only the medulla
1) Hypoglossal (CN XII)
2) Vagus (CN X)
3) Glossopharyngeal (CN IX)
The Accessory nerve was historically described as having 2 parts, but where are the SE motor neurons that innervate the trapezius and SCM located; where do they travel?
- Located in the cervical SC ONLY (C1-C6)
- Ascend into cranial cavity via foramen magnum
- Exit via the jugular foramen (w/ CN IX)
What is seen with a lesions of the CN XI root?
- Drooping of the shoulder (trapeizius paralysis) on ipsilateral side
- Difficult in turning head to the contralateral side (SCM paralysis) against resistance
What is damaged in regards to CN XI with lesions to the internal capsule, what deficits produced?
- Damage to the corticobulbar fibers relaying to the accessory nucleus
- Drooping of shoulder (ipsilateral), trouble turning head (contralateral)
- Primarily uncrossed —> ipsilateral deficits
Vagus nerve exits the cranial cavity via what foramen?
Jugular foramen
Which 2 ganglia lie immediately external to jugular foramen and which cell bodies does each contain?
- Superior ganglion contains the cell bodies of SA fibers
- Inferior ganglion contains the cells bodies of VA fibers
What 2 nuclei are supplying vagal motor fibers and to where?
-
Dorsal motor nucleus of the vagus:
- VE parasympathetic preganglionic targeting terminal (intramural) ganglia
- Visceral structures of the trachea/bronchi, heart, and digestive system - Nucleus ambiguus (SE): targeting pharyngeal and laryngeal targets + skeletal muscles in upper 1/2 esophagus
The VE parasympathetic preganglionic fibers of the Dorsal Motor Nucleus of Vagus target what ganglia and structures?
- Terminal (intramural) ganglia
- Visceral structures of the trachea and bronchi, heart, and digestive system just prox. to splenic flexure of colon
Somatic afferent input (pain and thermal) from a small area on the ear and part of the external auditory meatus, dura of the posterior cranial fossa innervated by Vagus have cell bodies where and utilize what tract?
- Cell bodies located in superior ganglion of the CN X
- Enter via medulla to join spinal trigeminal tract and synapse in spinal trigeminal nucleus
Where are the cell bodies for the visceral afferent and taste fibers of Vagus and which tract do they utilize, which terminates where?
- Cell bodies are located in the inferior ganglion of the vagus nerve
- Central processes enter the solitary tract and terminate in the surrounding caudal solitary nucleus
Lesion to the root of CN X results in?
- Dysphagia, owing to unilateral paralysis of pharyngeal and laryngeal musculature
- Dysarthria, owing to a weakness of laryngeal muscles and vocalis m.
Motor fibers of the glossopharyngeal nerve originate from which 2 nuclei?
- Inferior salivatory nucleus
- Nucleus ambiguus
The parasympathetic motor fibers of the glossopharyngeal nerve originiating from the inferior salivatory nucleus join which CN, synapse where, and supply what?
- Join w/ CN XI
- Synapse on VE postganglionic neurons (otic ganglion)
- Supply parotid gland
The SE fibers of glossopharyngeal originating from the nucleus ambiguus innervate what?
- Stylopharyngeus m.
- Participate as efferent limb of gag reflex (MINOR)
The SA fibers of glossopharyngeal originating from small area of the pinna, external auditory canal, and posterior 1/3 of tongue have cell bodies where and utilize which tract?
Cell bodies in superior ganglion –> Spinal trigeminal tract –> Spinal trigeminal nucleus
The VA sensory fibers of glossopharyngeal conveying info from parotid gland, oropharynx, and carotid body have cell bodies where and use which tract?
Cell bodies in inferior ganglion —> Solitary tract —> Solitary nucleus
What is glossopharyngeal neuralgia?
- Attacks of intense idiopathic pain arising from the sensory distribution of the nerve
- Pain in the oral cavity
Which CN’s are at risk by tumors or lesions near the jugular foramen?
CN IX, X, XI
Which CN’s are located at the Pons-Medulla junction?
- Vestibulocochlear (CN VIII)
- Facial (CN VII)
- Abducens (CN VI)
Which 2 motor nuclei are located at the pons-medulla junction?
- Abducens motor nucleus
- Facial motor nucleus
SE motor neurons from the Facial motor nucleus arch around what nucleus before exiting brainstem and are joined by axons from which nucleus?
- Arch around the abducens nucleus to exit brainstem
- Joined by axons from superior salivatory nucleus (VE preganglionic parasympathetic)
Which 2 nerve fibers emerge from the brainstem as 2 nerve bundles, and both form CN VII?
- Facial nerve fibers
- Intermediate nerve fibers
The abducens nucleus contains what 2 types of neurons; what do these neurons innervate?
- SE motor neurons innervate ipsilateral lateral rectus m.
- Interneurons send contralateral axons to the medial longitudinal fasciculus (MLF) –> target the contralateral oculomotor nucleus
A lesion of the Abducens nucleus results in what deficits?
- Damages motor neurons and interneurons
- Paralysis of the lateral rectus m. ipsilateral
- Failure of contralateral medial rectus m. to contract on attempted gaze toward the side of lesions
- Combines a LMN lesion w/ internuclear opthalmoplegia
The CN’s of the midbrain are exclusively motor, which supplies somatic efferents and which visceral efferents?
- Somatic efferents (both)
- Visceral efferents (CN III)
What is the ONLY motor CN that is formed entirely by axons that decussate before exit?
Trochlear Nerve (CN IV)
Where is the trochlear nucleus located and describe the route of the axons that leave here and what do they innervate?
- Situated posteriorly but adjacent to the MLF
- Axons arch around the periaqueductal gray, decussate, exit from posterior surface of the midbrain —> innervate contralateral Superior Oblique m.
Trochlear motor neurons innervate which eye muscle on which side?
The contralateral superior oblique m., because they decussate before exiting
Edinger-Westphal preganglionic nucleus sends fibers where, which gives off which nerves with what function?
- To the ciliary ganglion via CN III
- Gives off short ciliary nerves —> innervate sphincter pupillae and ciliary muscles
Lesions involving the oculomotor nucleus and oculomotor nerve produces SE motor and parasympathetic deficits, what are they?
- SE motor fibers paralyze ALL extraocular muscles in ipsilateral orbit, except for SO and LR
- Produces diplopia (double vision)
- Parasympathetic deficits: cause pupil dilation (mydriasis) and non-reactive to light
- Lens in ipsilateral eye cannot accomodate –> ciliary m. denervated
Upper motor neurons of the Corticonuclear system influence what 3 nuclei and associated CN’s?
1) Motor nuclei (CN V, VII, and XII)
2) Nucleus ambiguus (CN IX and X)
3) Accessory nucleus (CN XI)
Describe the course of the Corticonuclear tract, including the anatomical sites and regions of CNS it passes through; terminates at which CN nuclei?
- Corticonuclear axons funnel in genu of the internal capsuel and continue into cerebral peduncles
- Located medial to CST fibers
- Descend into pons and medulla –> exit bundle rostral to the cranial nerve nucleus –> then terminate at nuclei of CN V, VII, X, XII
How are muscles of the upper 1/2 of face vs. lower 1/2 of face controlled by Facial motor nuclei?
- Upper 1/2 of face controlled equally from both hemispheres
- Lower 1/2 of face controlled primarily from contralateral hemisphere
How does Supranuclear Facial Palsy (Central Facial Paralysis) differ from Bell (facial) Palsy?
- Supranuclear facial palsy: a lesion rostral to facial motor nucleus results in drooping of muscles at corner of mouth and lower face contralaterally
- Bell (facial) palsy: a lesion of root of facial nerve will result in flaccid paralysis of facial muscles of upper and lower portions of face on the ipsilateral side
Fibers distributed bilaterally to nucleus ambiguus, but motor innervation of soft palate/uvula is from the ________ side.
Contralateral
How do lesions to root of vagus (jugular foramen syndromes) affect the palatal arch muscles and uvula?
- Weakness and slight drooping of the arch ipsilateral to lesion
- Deviation of the uvula opposite the lesion at resk
- Acute deviation on phonation
U GO AWAY
Lesions to the hypoglossal nucleus cause the tongue to deviate to which side?
- Deviate toward lesion (contralateral) side, unopposed pull of intact muscle
- This is an UMN lesion
How will lesion of RIGHT corticonuclear fibers (UMN) targeting the hypoglossal nucleus affect the tongue?
- Tongue will deviate left (weak) side, opposite the lesion
- This is because the lesion is to the UMN which is contralateral
A lesion of medial medulla would affect what CN and tract, producing what deficits?
- Root of the CN XII, pyramid (corticospinal), and medial lemniscus
- Ipsilateral deviation of the tongue, contralateral hemiparesis (CST), contralateral loss of PCMLS
- Inferior alternating hemiplegia (medial medullary or Dejerine syndrome)
UMN lesions in fibers targeting nucleus ambiguus will cause what kind of deviation of palate/uvula?
- Deviation of palate/uvula ipsilateral to the lesion
- Uvula goes away from the side of lesion, when a LMN is involved.
- BUT this is a UMN lesion, and the UMN is contralateral the weak side, so the uvula is still deviating away from the weak side, but is toward the side of the UMN lesion
