Brainstem and Corticobulbar Pathways Flashcards
Which cranial nerves carry autonomics as one of their modalities?
CN III
CN VII
CN IX
CN X
Which cranial nerves are associated with the medulla oblongata?
Hypoglossal n.
Vagus n.
Glossopharyngeal n.
Axons of motor neurons from hypoglossal n. pass anteriorly in the medulla along the lateral aspect of the _____ ____ and the _______, continuing via the hypoglossal canal
Medial lemniscus; pyramid
What a. supplies the nucleus of the hypoglossal n?
Penetrating branches of anterior spinal a.
Muscles innervated by hypoglossal n.
Intrinsic tongue mm
Hyoglossus
Palatoglossus
Genioglossus
Result of lesions to hypoglossal nucleus
Tongue deviates contralateral to lesion when protruded
Result of injury to left hypoglossal n. (LMN)
Protruded tongue deviates left (ipsilateral to lesion)
Muscle atrophy and flaccid paralysis
Which n. sits in intermediate position of medulla oblongata between midline and lateral medulla?
Vagus n.
2 ganglia of vagus n. immediately external to jugular foramen — what are they and what cell bodies do they contain?
Superior ganglion = cell bodies of somatic afferent fibers
Inferior ganglion = cell bodies of visceral afferent fibers
What 2 nuclei are associated with motor fibers of vagus n.?
Dorsal motor nucleus of vagus (visceral efferent parasympathetics — preganglionic)
Nucleus ambiguus (somatic efferents)
Visceral efferent parasympathetic preganglionic fibers from vagus n. (Dorsal motor nucleus) targets the intramural ganglia of what visceral structures?
Trachea
Bronchi
Heart
Proximal GI tract (to sigmoid flexure of colon)
Nucleus ambiguus contains somatic efferent fibers of vagus n. What targets do these axons contact?
Pharyngeal and laryngeal targets
Skeletal m. in upper half of esophagus
2 types of sensory fibers associated with vagus n.
Somatic afferent input = pain and temp from small area on ear and part of external auditory meatus + dura of posterior cranial fossa
Visceral afferent and taste
Somatic afferent fibers of vagus n. enter via medulla to join the _____ tract and synapse in the corresponding nucleus
Spinal trigeminal
Visceral afferent and taste fibers of vagus n. have central processes that enter the ____ tract and terminate in the surrounding caudal corresponding nucleus
Solitary
CN X lesions at the root are also known as ______ syndrome.
What are the symptoms?
Jugular foramen syndrome
Dysphagia
Dysarthria
Weakness+slight drooping of ipsilateral palatal arch
Contralateral uvula deviation, acutely on phonation
[no lasting symptoms related to visceromotor/autonomic dysfunction]
Effect of nucleus ambiguus damage
Weakness of contralateral palatal arch mm
Slight drooping of contralateral palatal arch
Ipsilateral uvula deviation on attempted phonation
Somatic afferent fibers of the glossopharyngeal n. originate from small area on pinna and external auditory canal, and posterior 1/3 tongue. Cell bodies are in the _____ ganglion and fibers proceed via the ____ tract to the corresponding nucleus
Superior; spinal trigeminal
Visceral afferent fibers of the glossopharyngeal n. convey info from what structures?
Parotid gland
Oropharynx
Carotid body
Visceral afferent fibers of glossopharyngeal n. have cell bodies in the _____ ganglion which proceeds via _____ tract and targets the corresponding nucleus
Inferior; solitary
Lesions to the glossopharyngeal n. may affect what other nerve roots?
Vagus n
Accessory n.
[at jugular foramen]
Result of glossopharyngeal n. damage at jugular foramen
Diminished sense of taste from posterior tongue
Loss of ipsilateral stylopharyngeus m. contraction — gag reflex affected
Condition characterized by attacks of intense idiopathic pain arising from sensory distribution of CN IX
Glossopharyngeal neuralgia
Lesions of the medial medulla affect what structures?
Hypoglossal n.
Pyramid
Medial lemniscus
Effect of lesions of medial medulla
Ipsilateral tongue deviation and contralateral hemiparesis (CST involvement)
Contralateral loss of PCMLs
Inferior alternating hemiplegia (medial medullary or Dejerine syndrome)
Which CNs are associated with the pons-medullary junction (i.e., exit at caudal edge of pons)
Vestibulocochlear n.
Facial n.
Abducens n.
Somatic efferent fibers of facial n. arch around the _____ nucleus to exit the brainstem. They are joined by axons from the _____ nucleus
Abducens; superior salivatory (visceral efferent preganglionic parasympathetic)
Effect of lesion rostral to facial motor nucleus (UMN lesion)
Central facial paralysis aka supranuclear facial palsy
[causes drooping of contralateral corners of mouth and lower face]
Effect of lesion in root of facial n. (LMN lesion)
Bell’s palsy
[Flaccid paralysis of ipsilateral facial mm of upper and lower portions of the face]
The facial n. carries visceral afferent taste fibers from anterior 2/3 tongue. Associated cell bodies are in the ____ ganglion and fibers enter the ______ tract and terminate in the _____ nucleus
Geniculate; solitary; gustatory (of solitary nucleus)
Somatic afferent (cutaneous sensory) fibers from facial n. have cell bodies in _____ ganglion and central process enter the _____ tract and terminate in the associated nucleus
Geniculate; spinal trigeminal
The motor nucleus of the abducens n. is located internal to the ____ _____ and is surrounded by the internal genu of the ______ n.
Facial colliculus; facial
Somatic efferent fibers of the abducens n. innervate ipsilateral lateral rectus m. Interneurons send contralateral axons to the _____ ____ ____ which targets contralateral _____ nucleus
Medial longitudinal fasciculus (MLF); oculomotor
Which CNs do not recieve input from corticonuclear fibers?
Abducens n.
Trochlear n.
Oculomotor n.
Medial pontine syndrome causes injury to the abducens fibers in the pons. What effect does this have?
Flaccid paralysis of ipsilateral LR muscle
[Opposite eye still able to adduct bc interneurons are intact]
Result of lesion of abducens nucleus
Damage to motor neurons and interneurons—>
Paralysis of ipsilateral LR and failure of contralateral medial rectus muscle to contract on attempted gaze toward the side of the lesion
Combination of LMN lesion + internuclear ophthalmoplegia
Effect of damage to abducens interneurons only (in medial longitudinal fasciculus) as occurs with MS
Inability to adduct ipsilateral eye on attempted gaze contralaterally
Which CNs are associated with the midbrain?
Trochlear n.
Oculomotor n.
What is the only CN formed entirely by axons that decussate before exiting?
Trochlear n.
The trochlear nucleus is situated posteriorly but adjacent to the _____.
Somatic efferents innervate the contralateral superior oblique m. Axons arch around the _____ ______ before decussating, then exiting from posterior surface of the midbrain.
MLF
Periaqueductal gray
Lesions of trochlear n. root
Paralysis of ipsilateral SO m.
Lesions in midbrain involving MLF/trochlear nucleus
Paralysis of contralateral SO m.
Ipsilateral internuclear ophthalmoplegia
The oculomotor nucleus is located in the ventral portion of the _____ _____ in the rostral half of the midbrain.
The _____ _____ nucleus sends preganglionic parasympathetic fibers to the _____ ganglion via CN III
Periaqueductal gray; edinger-westphal; ciliary
Divisions of oculomotor n.
Superior and inferior + communicating branches to ciliary ganglion (give off short ciliary nn which innervate sphincter pupillae and ciliary mm)
Somatic efferent innervation from oculomotor n. provides ipsilateral innervation to extra-ocular mm. except for the ______ m.
Superior rectus
Lesions to oculomotor nucleus and nerve tend to have the same result. What are signs of this type of lesion?
Paralysis of ipsilateral extraocular muscles except superior oblique and lateral rectus
Diplopia
Parasympathetic deficits:
Mydriasis
Nonreactive pupils
Ipsilateral lens cannot accommodate
The accessory nerve does not have a cranial portion. Instead, where are the somatic efferent neurons located?
Cervical SC only! (C1-C6)
axons exit the lateral SC and ascend through the foramen magnum (briefly joining CN X) then exit jugular foramen
Lesions to accessory n. root
Ipsilateral drooping of shoulder, possible scapular winging
Difficulty turning head to contralateral side against resistance
Cervical cord lesions affecting accessory n.
Weakness of SCM and trap
[not especially obvious bc hemiplegia is more obvious manifestation of cervical cord lesions]
Internal capsule lesions affecting accessory n.
Ipsilateral drooping of shoulder, possible scapular winging
Difficulty turning head to contralateral side against resistance
Damage to corticobulbar fibers relaying to accessory nucleus (since these are primarily uncrossed, deficits are ipsilateral)
The corticonuclear (corticobulbar) system is organized in parallel with the _____
It consists of upper motor neurons that influence:
Motor nuclei of CN ____, ____, and _____
Nucleus ambiguus (CN ____ and _____)
Accessory nucleus (CN ____)
CST
V, VII, XII
IX, X
XI
Fiber types associated with corticobulbar tract
Medullary corticonuclear fibers
Pontine corticonuclear fibers
Mesencephalic corticonuclear fibers
For corticonuclear fibers to CN V and VII, axons funnel in the genu of the ____ ____ and continue into the _____ _____
They are located medial to CST fibers and descend into the pons and medulla, exiting rostral to their CN nucleus then terminate
Internal capsule; cerebral peduncles
For corticonuclear fibers to CN V and VII, _______ motor nuclei terminate on interneurons adjacent to nuclei, these nuclei send equal number of fibers bilaterally
Trigeminal
Result of unilateral damage to trigeminal motor nuclei
No discernable weakness of masticatory mm
How are the fibers of the facial motor nuclei associated with corticonuclear fibers different in terms of control of muscles in upper 1/2 vs. lower 1/2 the face
Muscles in upper 1/2 = controlled equally from both hemispheres
Muscles in lower 1/2 = controlled primarily from contralateral hemisphere
Corticonuclear fibers to CN X and XII: projections to _____ ____ are generally bilateral, but there are contralateral motor neuron projections to the _________
Nucleus ambiguus; soft palate/uvula
Corticonuclear fibers to CN XII pass superiorly to reach hypoglossal nuclei.
Fibers distribute bilaterally but innervation of _______ m. Is primarily contralateral
Genioglossus
Result of lesion of right corticonuclear fibers (UMN) assocated with CN XII
Protruded tongue will deviate contralaterally to lesion
Hemorrhage of lenticulostriate vessels on the right side results in what changes in extremities, face, uvula, tongue, and SCM/trap?
Left spastic hemiparesis of extremities Left central facial paralysis Right uvula deviation on phonation Left tongue deviation on protrusion Variable ipsilateral deficits on SCM and trap
Result of UMN lesions in fibers targeting nucleus ambiguus
Deviation of palate/uvula ipsilateral to lesion
Result of UMN lesions in fibers targeting hypoglossal nucleus
Protruded tongue to deviate opposite the lesion
Difference between direct and indirect corticonuclear fibers
Direct = fibers that project to cranial motor neurons
Indirect = fibers that project to midbrain- and pontine-reticular formations adjacent to CN nuclei
