Cranial Nerves 9,10,11,12 and Medulla Flashcards
(30 cards)
1
Q
Medulla is the site of the nuclei associated with Cranial Nerves:
A
9-12
2
Q
What is the location of where nerve fibers emerge from the medulla for cranial nerves 9-12 ?
A
- 9:
- 10:
- 11:
- 12:
3
Q
What are the motor and sensory components of cranial nerves 9-12?
A
- 9:
- 10:
- 11:
- 12:
4
Q
Where are the sites of origin and termination for each motor and sensory components for cranial nerves 9-12 and what are the functions of the components?
A
- 9:
- 10:
- 11:
- 12:
5
Q
What clinical defects are observed with unilateral lesion of cranial nerves 9-12?
A
- 9:
- 10:
- 11:
- 12:
6
Q
What is considered the closed medulla?
A
C1 to caudal end of the 4th ventricle
7
Q
Name the Nuclei involved in the closed medulla:
A
- inferior olivary nucleus or complex
- nucleus cuneatus & nucleus gracilis
- hypoglossal nucleus
- spinal trigeminal nucleus (spinal nucleus of V)
8
Q
name the 11 tracts represented in the closed medulla:
A
- pyramids
- spinothalamic tracts (spinal lemniscus)
- ventral trigeminothalamic tract
- fasciculus cuneatus, fasciculus gracilis
- medial longitudinal fascicles (MLF) (medial vestibulospinal tract)
- lateral vestibulospinal tract
- medial lemniscus
- internal arcuate fibers
- spinal trigeminal tract
- dorsal spinocerebellar
- hypoglossal nerve fibers
9
Q
name the nuclei represented in the Open medulla:
A
- inferior olivary nucleus
- spinal nucleus of V
- hypoglossal nucleus
- dorsal motor nucleus of the vagus (parasympathetic)
- nucleus ambiguous (lower motor neurons for CN IX and X)
- vestibular nuclei (medial and inferior)
- dorsal, ventral cochlear nucleus
10
Q
name the tracts represented in the open medulla:
A
- Pyramids
- medial lemniscus
- hypoglossal nerve fibers
- ventral trigeminothalamic tract
- medial vestibulospinal tract (MLF = medial longitudinal fasciculus)
- lateral vestibulospinal tract
- inferior cerebellar peduncle
- olivocerebellar fibers
- lateral spinothalamic tract
- spinal trigeminal tract
11
Q
Describe Cranial nerve XII (12 - Hypoglossal Nerve):
A
- motor neuron that supplies both intrinsic and extrinsic muscles of the tongue
- Lower Motor Neurons are located in the Hypoglossal Nucleus (nucleus is located near the midline of the medulla - ventral tot he central canal or 4th ventricle)
- Lower Motor Neuron axons pass inferolateral next to the medial lemniscus and pyramid to exit the medulla as rootlets in the ventrolateral (preolivary) sulcus adjacent to the pyramids
- Corticobulbar fibers (cortical control: Upper Motor Neurons) arise form the tongue region of the precentral gyrus (primary motor cortex) and descend with the corticospinal tract to the medulla where most of the fibers cross the midline and synapse in the contralateral hypoglossal nucleus
- the Hypoglossal Nucleus receives indirect sensory information from solitary nucleus (taste) and sensory trigeminal nuclei (bolus of food in the oral cavity) by way of the multisynaptic connections in the Reticular Formation. This reflex pathway controlling the tongue is involved in swallowing, suckling, and chewing.
12
Q
What would a lesion of the Lower Motor Neuron of the hypoglossal nerve or nucleus result in?
A
- paralysis and muscle wasting of both the intrinsic and extrinsic muscles on the ipsilateral side (SAME SIDE TONGUE MUSCLE PARALYSIS)
- during tongue protrusion, tongue will deviate toward the side of the lesion due to unopposed action of the intact contralateral gengioglossus muscle.
- patients will have difficulty eaten and speaking (dysarthria)
13
Q
What would a lesion of the Upper Motor Neuron of the hypoglossal nerve that occurs at the level prior to the crossing in the medulla result in?
A
- weakness of ONLY the extrinsic muscles (primarily genioglossus) on the side contralateral to the site of the lesion.
- tongue would protrude to the contralateral side of the lesion
14
Q
What is the hypoglossal nerve important for identifying?
A
strokes in the medulla
15
Q
A stroke to the paramedian branch of the anterior spinal artery may result in?
A
- combinations of damage to the hypoglossal nerve fibers, the adjacent pyramid, medial lemniscus and the ventral trigeminothalamic tract.
- results in a LMN symptom involving the tongue (deficit is noted ipsilateral deviation) and UMN symptoms involving the pyramid (deficit is noted contralaterally)
- This type of LMN and UMN combination of signs that is demonstrated on opposite sides of the neuraxis occurs where a motor cranial nerve exits along the midline adjacent to descending CORTICOSPINAL fibers. This is called ALTERNATING HEMIPLEGIA
16
Q
Describe Cranial Nerve XI (Accessory Nerve):
A
- contains a few LMNs in the nucleus ambiguus that innervate a few of the laryngeal muscles (cranial component)
- the cell bodies innervating the SCM and the trapezius muscles (spinal component) are located in the CERVICAL LEVELS of the spinal cord (dorsal to the ventral horn) (see picture)
- Axons of the spinal component leave the spinal cord and ascend into the cranial cavity through foramen magnum to re-exit the skull as the accessory nerve through the jugular foramen.
- for the cranial component, a small number of fibers exit the medulla along with the VAGUS NERVE
- Upper motor neurons (corticobulbar fibers) descend with the corticospinal fibers, cross over at the Pyramidal Decussation and terminate in the cervical region C2-C4
17
Q
Clinically, how do you test for involvement of the spinal part of CN XI?
A
the patient is asked to turn the head (SCM) or shrug the shoulders (Traps).
18
Q
T or F: the cranial component of the Accessory Nerve (XI) is indistinguishable from the Vagus Nerve
A
True.
19
Q
Name and describe the functional components of the Vagus Nerve (CN X):
A
- LOWER MOTOR NEURONS: located in the nucleus ambiguus innervate skeletal muscles of the soft palate, larynx and pharynx, including the vocalis muscle (true vocal folds). Nucleus ambiguus is located in the reticular formation and is not easily identified (a clue to its name). It contains LMNs for CN X and IX as ell as for the cranial part of CN XI
- PREGANGLIONIC PARASYMPATHETIC CELL BODIES: are located primarily in the dorsal motor nucleus of X. The axons exit the medulla as rootlets of X
20
Q
Name and describe the functional components of the Vagus Nerve (CN X):
A
- LOWER MOTOR NEURONS: located in the nucleus ambiguus innervate skeletal muscles of the soft palate, larynx and pharynx, including the vocalis muscle (true vocal folds). Nucleus ambiguus is located in the reticular formation and is not easily identified (a clue to its name). It contains LMNs for CN X and IX as ell as for the cranial part of CN XI
- PREGANGLIONIC PARASYMPATHETIC CELL BODIES: are located primarily in the dorsal motor nucleus of X. The axons exit the medulla as rootlets of X and synapse on postganglionic neuron in visceral walls of glands, cardiac muscle and smooth muscle of the thorax and abdomen
- SENSORY FIBERS: travel along the solitary tract to end in the solitary nucleus. This component is carrying pain and pressure from the pharynx, larynx, and thorax ad abdomen. Some of these fibers may enter the Spinal Trigeminal Nucleus (remember, pain of the face)
- UPPER MOTOR NEURONS: (corticobulbar) innervate the nucleus ambiguus bilaterally. Therefore, a unilateral lesion of the upper motor neurons would not be easily noticed.
21
Q
Name and describe the functional components of the Vagus Nerve (CN X):
A
- LOWER MOTOR NEURONS: located in the nucleus ambiguus innervate skeletal muscles of the soft palate, larynx and pharynx, including the vocalis muscle (true vocal folds). Nucleus ambiguus is located in the reticular formation and is not easily identified (a clue to its name). It contains LMNs for CN X and IX as ell as for the cranial part of CN XI
- PREGANGLIONIC PARASYMPATHETIC CELL BODIES: are located primarily in the dorsal motor nucleus of X. The axons exit the medulla as rootlets of X and synapse on postganglionic neuron in visceral walls of glands, cardiac muscle and smooth muscle of the thorax and abdomen
- SENSORY FIBERS: travel along the solitary tract to end in the solitary nucleus. This component is carrying pain and pressure from the pharynx, larynx, and thorax ad abdomen. Some of these fibers may enter the Spinal Trigeminal Nucleus (remember, pain of the face)
- UPPER MOTOR NEURONS: (corticobulbar) innervate the nucleus ambiguus bilaterally. Therefore, a unilateral lesion of the upper motor neurons would not be easily noticed.
22
Q
Name and describe the important reflexes mediated by parts of the Vagus Nerve (X):
A
- CAROTID SINUS REFLEX: CN X carries the efferent part of this reflex arc to the heart. The afferent limb originates from BARORECEPTORS along the carotid artery near the bifurcation into internal and external carotid arteries. The afferent information is carried by fibers of CN IX to the solitary nucleus, then relayed to the dorsal motor nucleus of X. This efferent limb of the reflex arc innervates the heart to slow heartrate.
- CAROTID BODY REFLEX: a complex reflex that uses CN X to carry one sensory (afferent) component, the chemoreceptor sensation from the lung bronchioles, which synapse in the “medullary respiratory center” (an area in the reticular formation). This reflex helps control breathing rhthym. The efferent limb is via descending information to spinal cord levels controlling inspiration (intercostals and diapraghm)
- COUGH, GAG, AND VOMITING REFLEXES: complex reflexes involving sensory fibers form oral/nasal cavity (CN IX) or the gut (CN X). Sensory information is relayed to appropriate LMNs in nucleus ambiguus and spinal cord, and preganglionic parasympathetics in dorsal motor nucleus of X.
23
Q
What do lesions of CN X (Vagus) result in?
A
Both sensory and motor deficits
24
Q
A unilateral lesion of the LMNs of the CN X results in what?
A
difficulty in swallowing, hoarseness (dysphonia), inability to raise the soft palate on ipsilateral side.
25
What do lesions of the preganglionic parasympathetic fibers of CN X cause?
cause disruption of some gut reflexes, but are less important for diagnosis of lesion location than are deficits associated with somatomotor LMN component. Hyperactivity (excess firing) can cause excess gastric acid secretions (ulcers)
26
What would a large bilateral lesions of the medullary reticular formation cause?
can disrupt normal breathing rhythms an reflex control of vascular resistance to blood flow and result in coma. Patients with this type of damage may need life support systems and have poor prognosis.
27
Name and describe the functional components of CN IX (9: Glossopharyngeal nerve):
- LOWER MOTOR NEURONS: for the stylopharyngeus muscle; LMNs located in rostral end of Nucleus Ambiguus.
- PREGANGLIONIC PARASYMPATHETIC neuron cell bodies located for innervation of the parotid gland.
- SENSORY NEURONS: central processes synapse in the caudal part of the Solitary Nucleus; carries the afferent limb of the carotid sinus reflexes -- central processes synapse in sensory trigeminal nuclei; primarily spinal nucleus of V; carries somatic sensations (tough pressure, pain) from pharynx and posterior 1/3 of tongue (gag reflex). This portion also carries taste sensation form posterior 1/3 of tongue (mainly bitter sensation) to rostral part of solitary nucleus.
- CORTICAL CONTROL (UMN): in cortex descends as part of corticobulbar system to synapse bilaterally on LMNs in nucleus ambiguus.
- REFLEXES: CN IX carries the afferent (sensory) limb for several reflexes whose efferent limb is carried by CN X, CN XII, and/or spinal cord LMNs. These include carotid sinus, gag, vomiting and swallowing reflexes. Also, the motor components of IX participate in swallowing and salvation - taste reflexes.
28
Name Cranial Nerves that have LMNs located in the Nucleus Ambiguus:
- CN X
| - CN IX
29
What are some clinical considerations for Cranial nerve IX?
- can produce difficulty with speech and swallowing but deficits are less severe than with CN X lesions
- Some visceral reflexes can be impaired as with CN X lesions
- WHAT SETS IT APART FROM CN X LESION: most diagnostic deficits which distinguish between IX and CN X lesions are loss of gag reflex to touching the pharynx (CN IX, afferent limb) compared to deviation of uvula (CN X, efferent limb)
30
Where is the majority of the CN IIIV pathway found?
in the pons
