Cranial Nerves - Medulla Flashcards
What is Cranial Nerve XII?
Hypoglossal Nerve
Is CN XII Hypoglossal sensory or motor?
motor
What does CN XII Hypoglossal supply?
both intrinsic and extrinsic muscles of the tongue
Where are the cell bodies of the LMN of CN XII Hypoglossal located?
Hypoglossal Nucleus
Where is the Hypoglossal Nucleus located?
near the midline of the medulla (ventral to the central canal or 4th ventricle)
Where do the CN XII Hypoglossal LMN axons pass and in relation to what two structures?
The axons pass inferolateral next to the medial lemniscus and pyramid
Where do the CN XII Hypoglossal LMN axons exit the medulla?
as rootlets in the ventrolateral (preolivary) sulcus
What are UMN of CN XIII Hypoglossal known as?
Corticobulbar fibers (cortical control)
Where do CN XIII Hypoglossal UMN Corticobulbar fibers arise from?
tongue region of the precentral gyrus (Primary motor cortex)
Where do CN XIII Hypoglossal UMN Corticobulbar fibers descend
with the corticospinal tract to the medulla
What do most of the CN XIII Hypoglossal UMN Corticobulbar fibers do at the medulla and where do they synapse?
most of the fibers cross the midline and synapse in the contralateral hypoglossal nucleus.
Where does the hypoglossal nucleus receive indirect sensory information from and what type of info?
Solitary Nucleus (Taste)
and
Sensory Trigeminal Nuclei (bolus of food in oral cavity)
How does the hypoglossal nucleus receive indirect sensory information from the Solitary Nucleus and Sensory Trigeminal Nuclei?
by way of multisynaptic connections in the reticular formation
What is this reflex pathway of controlling the tongue involved in?
swallowing, suckling, and chewing
Clinically, what does a LMN lesion of the CN XIII Hypoglossal or nucleus result in?
paralysis and muscle wasting of both intrinsic and extrinsic muscles on the ipsilateral side.
How does the tongue respond in a LMN lesion of CN XIII Hypoglossal?
upon protrusion of the tongue, it deviates toward the side of the lesion due to the unopposed action of the intact contralateral genioglossus muscle.
What will patients have difficulty with in a LMN lesion of the CN XIII Hypoglossal?
eating and speaking (dysarthria)
Clinically, what does a UMN lesion of the CN XIII Hypoglossal that occurs at a level prior to the crossing result in?
results in weakness of only the extrinsic muscles (primarily genioglossus) on the side contralteral to the site of the lesion.
Which way will the tongue deviate upon voluntary protrusion in a UMN lesion of the CN XIII Hypoglossal that occurs at a level prior to the crossing?
it deviates away from the side of the lesion due to the crossing fibers and unopposed action of the intact contralateral genioglossus muscle
A stroke of the paramedian branch of the anterior spinal artery may result in combinations of damage to the
- hypoglossal nerve fibers,
- the adjacent pyramid
- medial lemniscus
- ventral trigeminothalamic tract
Would would be the result of a stroke of the paramedian branch of the anterior spinal artery - hypoglossal nerve fibers?
LMN symptoms involving the tongue
-paralysis and muscle wasting of both intrinsic and extrinsic muscles on the ipsilateral side
Would would be the result of a stroke of the paramedian branch of the anterior spinal artery - hypoglossal nerve fibers -the adjacent pyramid?
UMN symptoms involving the pyramid
Contralateral axial and appendicular musculature - Initial flaccid paralysis followed by: Abnormal cutaneous reflexes (Babinski sign), Abnormal reflexes: clonus, clasp knife), Spasticity – velocity dependent hypertonia, Abnormal timing of muscle activation (slower onset, prolonged contraction), Paresis or plegia (weakness)
(corticospinal fibers prior to decussating and forming the lateral corticospinal tract)
Would would be the result of a stroke of the paramedian branch of the anterior spinal artery - hypoglossal nerve fibers -medial lemniscus?
Loss of Contralateral Body Sense:
- Sterogenesis
- -Conscious Proprioception
- -Two Point Discriminative Touch
- Vibratory
Would would be the result of a stroke of the paramedian branch of the anterior spinal artery -ventral trigeminothalamic tract?
Somatosensation of the Face by CN V Trigeminal Nerve
Contrallateral loss of Nociception and Thermal Sensation
Contralteral Touch (discriminative and light non-discriminative) and Conscious Proprioception should be preserved due to bilateral represetation via dorsal trigeminothalamic tract?
What is alternating hemiplegia?
Combination of lower and upper motor neuron signs that are demonstrated on opposite sides of the neuraaxis as seen with a stroke with the paramedian branch of anterior spinal artery.
Where are the regions that alternating hemiplegia occur?
Where a motor cranial nerve exits along the midline adjacent to the descending corticospinal fibers.
What are the two other likely regions this might occur?
III - Oculomotor
VI - Abducens
although these two are for tongue?
VII - Facial Nerve
XI - Glossopharyngeal
CNXI - Accessory Nerve contains a few LMN in ___
nucleus ambiguus
CNXI - Accessory Nerve LMN in nucleus ambiguus innervate a few of the ____
laryngeal muscles (cranial component)
CNXI - Accessory Nerve cell bodies innervating the sternocleidomastoid and trapezius muscles (spinal components) are located in
cervical levels of the spinal cord dorsal to the ventral horn
Where do CNXI - Accessory Nerve axons of the spinal component go?
they leave the spinal cord and ascend into the cranial cavity to re-exit the skull as the accessory nerve
Where do CNXI - Accessory Nerve axons of the cranial comonent go?
a small number of fibers exit the medulla long with the vagus nerve.
CNXI - Accessory Nerve UMN (corticobulbar fibers) descend with the ___
corticospinal fibers
After CNXI - Accessory Nerve descend with the corticospinal fibers they ___
decussate at the pyramidal decussation
Where do CNXI - Accessory Nerve terminate?
in the cervical region (C2-4)
Clinically, how do you test for involvement of the spinal part of CNXI - Accessory Nerve?
the patient is asked to turn the head (sternocleidomastoid) or shrug the shoulders (trapezius).
T/F: The cranial component of CNXI - Accessory Nerve is indistinguishable from CNX - Vagus Nerve?
True
CNX - Vagus Nerve UMN (corticobulbar) innervate ___
nucleus ambiguus
CNX - Vagus Nerve UMN (corticobulbar) innervate nucleus ambiguus ipsilaterally, contralaterally, or bilaterally?
bilaterally i.e., both sides.
T/F: because CNX - Vagus Nerve UMN innervates nucleus ambiguus bilaterally, a unilateral lesion of the upper motor neuron can be easily distinguished.
FALSE: a unilateral lesion of the upper motor neuron would not be easily distinguished
CNX - Vagus Nerve LMN located in nucleus ambiguus innervate what? (3)
Skeletal Muscles of the 1. Soft Palate 2. Larynx 3. Pharynx including vocalis muscle (true vocal folds).
Where is Nucleus ambiguus located?
reticular formation
T/F: Nucleus Ambiguus is not easily identified.
True
Nucleus Ambiguus contains lower motor neurons for what Cranial Nerves? (3)
CN IX - Glossopharyngeal
CN X - Vagus
Cranial Part of CN XI - Accessory Nerve
Where are preganglionic parasympathetic cell bodies for CNX - Vagus Nerve located primarily?
in the dorsal motor nucleus of X
The preganglionic parasympathetic axons for CNX - Vagus Nerve go from the cell bodies on dorsal motor nucleus of X and ____
exit the medulla as rootlets of X
Where do the axons of the preganglionic parasympathetic axons for CNX - Vagus Nerve synapse?
on postganglionic neurons in visceral walls of glands, cardiac muscle, and smooth muscle of the throax and abdomen.
CNX - Vagus Nerve sensory fibers travel along the
solitary tract
CNX - Vagus Nerve sensory fibers travel along the solitary tract and end in the
solitary nucleus
CNX - Vagus Nerve sensory fibers component carry
pain and pressure from pharynx, larynx, thorax, and abdomen
Where do some of the CNX - Vagus Nerve sensory fibers enter and why?
Spinal Trigeminal Nucleus because pain of the face.
What are the three important reflexes carried by the CNX - Vagus Nerve?
- Carotid Sinus Reflex
- Carotid Body Reflex
- Cough, gag, and vomiting reflexes
Carotid Sinus Reflex - Where does the afferent limb originate?
from baroreceptors along the carotid artery near the bifurcation into internal and carotid arteries
Carotid Sinus Reflex - Which cranial nerve carries afferent information?
fibers of CN IX - Glossopharyngeal
Carotid Sinus Reflex - CN IX - Glossopharyngeal carries afferent information to
solitary nucleus
Carotid Sinus Reflex - CN IX - Glossopharyngeal carries afferent information to solitary nuclues, then relayed to the
dorsal motor nucleus of X
Carotid Sinus Reflex - Which cranial nerve carries efferent information?
CNX - Vagus
Carotid Sinus Reflex - The efferent limb, CNX - Vagus, of the reflex arc innervates what and does what?
the heart to slow heart rate
Carotid Body Reflex - uses what cranial nerve for one of its sensory afferent components?
CNX - Vagus
Carotid Body Reflex - What sensory afferent information does CNX - Vagus carry?
the chemoreceptor sensation from lung bronchioles
Carotid Body Reflex - What sensory afferent information does CNX - Vagus carry chemoreceptor sensation from lung bronchioles, which synapse in the
“medullary respiratory center” (an area in the reticular formation)
Carotid Body Reflex - What does it help control?
breathing rhythm
Carotid Body Reflex - The efferent limb carries what information where?
descending information to spinal cord levels controlling inspiration (intercostals and diaphragm)
Cough, gag, and vomiting reflexes - involves sensory fibers from what two cranial nerves from where?
CNIX - Glossopharyngeal (oral/nasal cavity)
CNX - Vagus (gut)
Cough, gag, and vomiting reflexes - where is the sensory information relayed?
to appropriate lower motor neurons in nucleus ambiguus and spinal cord, and preganglionic parasympathetics in dorsal motor nucleus of X
Do lesions of CNX - Vagus Nerve result in sensory or motor deficits?
both sensory and motor deficits
Unilateral lesions of lower motor neurons of CNX - Vagus result in ___ (3)
- Difficulty swallowing
- Hoarseness (dysphonia)
- inability to raise the soft palate on ipsilateral side
Lesions of the preganglionic parasympathetic fibers of CNX - Vagus Nerve cause
disruption of some gut reflexes (but are less important for diagnosis of lesion location than are deficits assocaited with somatomotor LMN component).
Hyperactivity (excess firing) of preganglionic parasympathetic fibers of CNX - Vagus Nerve can cause
excess gastric acid secretion = ulcers
Large bilateral lesions of the medullary reticular formation can
disrupt normal breathing rhythms and reflex control of vascular resistance to blood flow and result in coma.
Patient with this type of damage may need life support systems and have a poor prognosis.
CNIX - Glossopharyngeal Nerve cortical control UMN in cortex descends as part of
corticobulbar synapses
CNIX - Glossopharyngeal Nerve cortical control UMN in cortex descends as part of corticobulbar system to synapse on
lower motor neurons in nucleus ambiguus
CNIX - Glossopharyngeal Nerve UMN synapses on nucleus ambiguus ipsilaterally, contralaterally, or bilaterally?
bilaterally
Where are CNIX - Glossopharyngeal Nerve LMN’s located in nucleus ambiguus?
rostral end
What cranial nerves have LMN’s in Nucleus Ambiguus?
CN IX - Glossopharyngeal
CN X - Vagus
Cranial Part of CN XI - Accessory Nerve
CNIX - Glossopharyngeal Nerve LMN from nucleus ambiguus innervate
stylopharyngeus muscle
CNIX - Glossopharyngeal Nerve preganglionic parasympathetic neuron cell bodies located in
reticular formation
CNIX - Glossopharyngeal Nerve preganglionic parasympathetic neuron cell bodies located in reticular formation; axons exit the
medulla
CNIX - Glossopharyngeal Nerve preganglionic parasympathetic neuron cell bodies located in reticular formation; axons exit the medulla to synapse on
postganglionic neurons in otic ganglion
CNIX - Glossopharyngeal preganglionic parasympathetic nerves from the otic ganglion then innervate
the parotid gland (remember from anatomy that this component follows the auriculotemporal branch of V3
CNIX - Glossopharyngeal sensory neurons central processes synapse in the (2)
- caudal part of the solitary nucleus
2. sensory trigeminal nuclei; primarily spinal nucleus of V
CNIX - Glossopharyngeal sensory neurons central processes synapse in the caudal part of solitary nucleus and carry
the afferent limb of the carotid sinus reflexs
CNIX - Glossopharyngeal sensory neurons central processes synapse in the sensory trigeminal nuclei; primarily spinal nucleus of V carries
somatic sensations (touch, pressure, pain) from pharynx and posterior 1/3 of tongue (gag reflex)
CNIX - Glossopharyngeal sensory neurons central processes synapse in the sensory trigeminal nuclei; primarily spinal nucleus of V carries what information to anterior part of solitary nucleus?
taste sensation from posterior 1/3 of tongue (mainly bitter sensation)
CNIX - Glossopharyngeal carries the afferent or efferent limb for several reflexes?
afferent (sensory)
CNIX - Glossopharyngeal is the efferent limb for several reflexes whose efferent limb is carried by (3)
CNX - Vagus
CNXII - Hypoglossal
Spinal Cord LMN’s
What reflexes does CNIX - Glossopharyngeal carry afferent (sensory) information for? (4)
Carotid Sinus Reflex
Gag Reflex
Vomiting Reflex
Swallowing Reflex
The motor component of CNIX - Glossopharyngeal participates in what reflexes? (2)
Swallowing Reflex
Salivation-Taste Reflex
Unilateral lesions of CNIX - Glossopharyngeal can produce
difficulty with speech and swallowing
T/F: defitis from unilateral lesions from CNIX - Glossopharyngeal are less severe than with CNX - Vagus Nerve.
True
Similar to CNX - Vagus, CNIX - Glossopharyngeal lesions can result in
some visceral reflexes
What is the most diagnostic deficits which distinguish between CNIX - Glossopharyngeal and CNX - Vagus lesions?
Loss of gag reflex to touching the pharynx compared to deviation of uvula
Loss of gag reflex to touching the pharynx would indicate a lesion with
CNIX - Glossopharyngeal (afferent limb)
Loss of deviation of uvula would indicate a lesion with
CNX - Vagus (efferent limb)
