Brainstem and Corticobulbar Pathways

Question 1

Which cranial nerves carry autonomics as one of their modalities?

Answer 1

CN III
CN VII
CN IX
CN X

Question 2

Which cranial nerves are associated with the medulla oblongata?

Answer 2

Hypoglossal n.
Vagus n.
Glossopharyngeal n.

Question 3

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

Answer 3

Medial lemniscus; pyramid

Question 4

What a. supplies the nucleus of the hypoglossal n?

Answer 4

Penetrating branches of anterior spinal a.

Question 5

Muscles innervated by hypoglossal n.

Answer 5

Intrinsic tongue mm
Hyoglossus
Palatoglossus
Genioglossus

Question 6

Result of lesions to hypoglossal nucleus

Answer 6

Tongue deviates contralateral to lesion when protruded

Question 7

Result of injury to left hypoglossal n. (LMN)

Answer 7

Protruded tongue deviates left (ipsilateral to lesion)

Muscle atrophy and flaccid paralysis

Question 8

Which n. sits in intermediate position of medulla oblongata between midline and lateral medulla?

Answer 8

Vagus n.

Question 9

2 ganglia of vagus n. immediately external to jugular foramen — what are they and what cell bodies do they contain?

Answer 9

Superior ganglion = cell bodies of somatic afferent fibers

Inferior ganglion = cell bodies of visceral afferent fibers

Question 10

What 2 nuclei are associated with motor fibers of vagus n.?

Answer 10

Dorsal motor nucleus of vagus (visceral efferent parasympathetics — preganglionic)

Nucleus ambiguus (somatic efferents)

Question 11

Visceral efferent parasympathetic preganglionic fibers from vagus n. (Dorsal motor nucleus) targets the intramural ganglia of what visceral structures?

Answer 11

Trachea
Bronchi
Heart
Proximal GI tract (to sigmoid flexure of colon)

Question 12

Nucleus ambiguus contains somatic efferent fibers of vagus n. What targets do these axons contact?

Answer 12

Pharyngeal and laryngeal targets

Skeletal m. in upper half of esophagus

Question 13

2 types of sensory fibers associated with vagus n.

Answer 13

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

Question 14

Somatic afferent fibers of vagus n. enter via medulla to join the _____ tract and synapse in the corresponding nucleus

Answer 14

Spinal trigeminal

Question 15

Visceral afferent and taste fibers of vagus n. have central processes that enter the ____ tract and terminate in the surrounding caudal corresponding nucleus

Answer 15

Solitary

Question 16

CN X lesions at the root are also known as ______ syndrome.

What are the symptoms?

Answer 16

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]

Question 17

Effect of nucleus ambiguus damage

Answer 17

Weakness of contralateral palatal arch mm
Slight drooping of contralateral palatal arch
Ipsilateral uvula deviation on attempted phonation

Question 18

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

Answer 18

Superior; spinal trigeminal

Question 19

Visceral afferent fibers of the glossopharyngeal n. convey info from what structures?

Answer 19

Parotid gland
Oropharynx
Carotid body

Question 20

Visceral afferent fibers of glossopharyngeal n. have cell bodies in the _____ ganglion which proceeds via _____ tract and targets the corresponding nucleus

Answer 20

Inferior; solitary

Question 21

Lesions to the glossopharyngeal n. may affect what other nerve roots?

Answer 21

Vagus n
Accessory n.

[at jugular foramen]

Question 22

Result of glossopharyngeal n. damage at jugular foramen

Answer 22

Diminished sense of taste from posterior tongue

Loss of ipsilateral stylopharyngeus m. contraction — gag reflex affected

Question 23

Condition characterized by attacks of intense idiopathic pain arising from sensory distribution of CN IX

Answer 23

Glossopharyngeal neuralgia

Question 24

Lesions of the medial medulla affect what structures?

Answer 24

Hypoglossal n.
Pyramid
Medial lemniscus

Question 25

Effect of lesions of medial medulla

Answer 25

Ipsilateral tongue deviation and contralateral hemiparesis (CST involvement) Contralateral loss of PCMLs Inferior alternating hemiplegia (medial medullary or Dejerine syndrome)

Question 26

Which CNs are associated with the pons-medullary junction (i.e., exit at caudal edge of pons)

Answer 26

Vestibulocochlear n. Facial n. Abducens n.

Question 27

Somatic efferent fibers of facial n. arch around the _____ nucleus to exit the brainstem. They are joined by axons from the _____ nucleus

Answer 27

Abducens; superior salivatory (visceral efferent preganglionic parasympathetic)

Question 28

Effect of lesion rostral to facial motor nucleus (UMN lesion)

Answer 28

Central facial paralysis aka supranuclear facial palsy [causes drooping of contralateral corners of mouth and lower face]

Question 29

Effect of lesion in root of facial n. (LMN lesion)

Answer 29

Bell’s palsy [Flaccid paralysis of ipsilateral facial mm of upper and lower portions of the face]

Question 30

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

Answer 30

Geniculate; solitary; gustatory (of solitary nucleus)

Question 31

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

Answer 31

Geniculate; spinal trigeminal

Question 32

The motor nucleus of the abducens n. is located internal to the ____ _____ and is surrounded by the internal genu of the ______ n.

Answer 32

Facial colliculus; facial

Question 33

Somatic efferent fibers of the abducens n. innervate ipsilateral lateral rectus m. Interneurons send contralateral axons to the _____ ____ ____ which targets contralateral _____ nucleus

Answer 33

Medial longitudinal fasciculus (MLF); oculomotor

Question 34

Which CNs do not recieve input from corticonuclear fibers?

Answer 34

Abducens n. Trochlear n. Oculomotor n.

Question 35

Medial pontine syndrome causes injury to the abducens fibers in the pons. What effect does this have?

Answer 35

Flaccid paralysis of ipsilateral LR muscle [Opposite eye still able to adduct bc interneurons are intact]

Question 36

Result of lesion of abducens nucleus

Answer 36

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

Question 37

Effect of damage to abducens interneurons only (in medial longitudinal fasciculus) as occurs with MS

Answer 37

Inability to adduct ipsilateral eye on attempted gaze contralaterally

Question 38

Which CNs are associated with the midbrain?

Answer 38

Trochlear n. | Oculomotor n.

Question 39

What is the only CN formed entirely by axons that decussate before exiting?

Answer 39

Trochlear n.

Question 40

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.

Answer 40

MLF Periaqueductal gray

Question 41

Lesions of trochlear n. root

Answer 41

Paralysis of ipsilateral SO m.

Question 42

Lesions in midbrain involving MLF/trochlear nucleus

Answer 42

Paralysis of contralateral SO m. | Ipsilateral internuclear ophthalmoplegia

Question 43

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

Answer 43

Periaqueductal gray; edinger-westphal; ciliary

Question 44

Divisions of oculomotor n.

Answer 44

Superior and inferior + communicating branches to ciliary ganglion (give off short ciliary nn which innervate sphincter pupillae and ciliary mm)

Question 45

Somatic efferent innervation from oculomotor n. provides ipsilateral innervation to extra-ocular mm. except for the ______ m.

Answer 45

Superior rectus

Question 46

Lesions to oculomotor nucleus and nerve tend to have the same result. What are signs of this type of lesion?

Answer 46

Paralysis of ipsilateral extraocular muscles except superior oblique and lateral rectus Diplopia Parasympathetic deficits: Mydriasis Nonreactive pupils Ipsilateral lens cannot accommodate

Question 47

The accessory nerve does not have a cranial portion. Instead, where are the somatic efferent neurons located?

Answer 47

Cervical SC only! (C1-C6) axons exit the lateral SC and ascend through the foramen magnum (briefly joining CN X) then exit jugular foramen

Question 48

Lesions to accessory n. root

Answer 48

Ipsilateral drooping of shoulder, possible scapular winging Difficulty turning head to contralateral side against resistance

Question 49

Cervical cord lesions affecting accessory n.

Answer 49

Weakness of SCM and trap [not especially obvious bc hemiplegia is more obvious manifestation of cervical cord lesions]

Question 50

Internal capsule lesions affecting accessory n.

Answer 50

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)

Question 51

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 ____)

Answer 51

CST V, VII, XII IX, X XI

Question 52

Fiber types associated with corticobulbar tract

Answer 52

Medullary corticonuclear fibers Pontine corticonuclear fibers Mesencephalic corticonuclear fibers

Question 53

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

Answer 53

Internal capsule; cerebral peduncles

Question 54

For corticonuclear fibers to CN V and VII, _______ motor nuclei terminate on interneurons adjacent to nuclei, these nuclei send equal number of fibers bilaterally

Answer 54

Trigeminal

Question 55

Result of unilateral damage to trigeminal motor nuclei

Answer 55

No discernable weakness of masticatory mm

Question 56

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

Answer 56

Muscles in upper 1/2 = controlled equally from both hemispheres Muscles in lower 1/2 = controlled primarily from contralateral hemisphere

Question 57

Corticonuclear fibers to CN X and XII: projections to _____ ____ are generally bilateral, but there are contralateral motor neuron projections to the _________

Answer 57

Nucleus ambiguus; soft palate/uvula

Question 58

Corticonuclear fibers to CN XII pass superiorly to reach hypoglossal nuclei. Fibers distribute bilaterally but innervation of _______ m. Is primarily contralateral

Answer 58

Genioglossus

Question 59

Result of lesion of right corticonuclear fibers (UMN) assocated with CN XII

Answer 59

Protruded tongue will deviate contralaterally to lesion

Question 60

Hemorrhage of lenticulostriate vessels on the right side results in what changes in extremities, face, uvula, tongue, and SCM/trap?

Answer 60

``` 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 ```

Question 61

Result of UMN lesions in fibers targeting nucleus ambiguus

Answer 61

Deviation of palate/uvula ipsilateral to lesion

Question 62

Result of UMN lesions in fibers targeting hypoglossal nucleus

Answer 62

Protruded tongue to deviate opposite the lesion

Question 63

Difference between direct and indirect corticonuclear fibers

Answer 63

Direct = fibers that project to cranial motor neurons Indirect = fibers that project to midbrain- and pontine-reticular formations adjacent to CN nuclei