Cranial Nerves and Nuclei Flashcards
Where are the nuclei of each cranial nerve located and what is the exception?
The same rostral-caudal level as the nerve entry/exit point
Except the trigeminal nerve
Where does the optic nerve carry visual information to?
The superior colliculi and the pretectal area
What are the two functional components of CN III?
Somatic motor - extraocular muscles
Visceral motor - pupillary constrictor and ciliary muscles
Where is the oculomotor nucleus?
Medial tegmentum in the rostral midbrain at the level of the superior colliculi
What is the Edinger-Westphal nucleus and where is it located?
Preganglionic parasympthetic cell bodies for CN III
Located dorsally to the oculomotor nucleus
What is the pathway of the pupillary light reflex?
Retinal ganglion cell axons from both eyes carry information (via CN II) to the pretectal area on each side
The pretectal area projects bilaterally to the Edinger-Westphal nucleus with the contralateral projection traveling through the posterior commisure
Motor output is conveyed by the EW nucleus to the ciliary ganglion
What is the result of a unilateral deficit in the motor output of the pupillary light reflex?
An eye with impaired pupillary constriction in response to light stimulation of either eye
Describe the pupillary light reflex in horner’s syndrome.
Both direct and consensual pupillary constriction can be observed in response to light stimulation
The affected eye will have reduced and slowed dilation when the light is removed
Describe the pupillary light reflex with a unilateral afferent defect.
The affected eye will be unable to detect of conduct light sensation
Will cause loss of direct and consensual response when the affected eye is stimulated
When unaffected eye is stimulated, both direct and consensual responses will occur
What is benign essential anisocoria?
Pupils which have unequal diameters under all lighting conditions and no dilation lag when going from light to dark
Present in approximately 20% of the population
What is the result of a complete unilateral lesion of CN III?
Diplopia - loss of extraocular muscle tone
Ptosis - paralysis of levator palpebrae superior
Dilated pupil
What are false localizing signs?
Neurological signs that reflect dysfunction distant from the expected locus of injury
E.g. uncal herniation can cause a CN III nerve sign even though the site of hemorrhage is distant from CN III
Where are the trochlear nuclei?
Midbrain tegmentum, near the midline and just ventral to the periqueductal grey
More caudal, at the level of the inferior colliculi
What is the result of a lesion to the trochlear nerve?
Diplopia due to elevation and extortion of the affected eye
Patient may compensate by tucking chin and tilting head
What are the two functional components of the trigeminal nerve?
Somatic Sensory
Branchial Motor
Where is the chief sensory nucleus (V) and what kind of input does it receive?
The lateral pons, at the level that the trigeminal nerve fibers enter
Receives input from sensory fibers carrying discriminative touch, pressure, and vibration
(analogous to the medial lemniscus pathway
Where is the spinal trigeminal nucleus (V) and what kind of input does it receive?
Lateral, extends from the mid pons to the upper cervical spinal cord
Crude touch, pain, temperature
How is the face represented in the spinal trigeminal nucleus?
“Onion skin” -like pattern with concentric rings centered on the mouth
The mouth is represented most rostrally, and areas furthest from the mouth most caudally in the nucleus
Where is the mesencephalic trigeminal nucleus located and what kind of input does it receive?
Laterally, extends from mid-pons into the midbrain where it is located along the lateral edge of the periaqueductal grey
Propioception
Where do primary sensory neurons in the mesencephalic trigeminal nucleus send their output?
Tigeminal motor nucleus
Mediates the jaw jerk reflex
Where is the trigeminal motor nucleus?
Mid-pons level, medial to the chief sensory nucleus
Contains LMNs for the brachial motor functions
What is trigeminal neuralgia?
Chronic pain condition, typical (1) and atypical (2) forms
Differentiated by pain symptoms (sporadic vs. constant, shock-like vs. burning)
Pain can be extreme and incapacitating
What is shingles?
Pain condition that can involve the trigeminal nerve caused by herpes zoster
Vision loss is possible
What is the function of CN VI?
Somatic motor innervation to the lateral rectus
Where is the abducens nucleus located?
Caudal pons
Under the facial colliculus
What occurs as a result of a lesion to CN VI?
Inability to abduct the ipsilateral eye
Resting medial strabismus
What are the four functional components of the facial nerve?
Branchial motor
Parasympathetic
Visceral sensory
Somatic sensory
What is the function of the facial nucleus?
Contains LMNs which innervate the branchial muscles
What is the function of the superior salivary nucleus?
Origin of the preganglionic parasympathetic fibers of the facial nerve
What is the location and function of the solitary nucleus?
Extends from the caudal pons through most of the medulla
Rostral portion receives input from taste afferents
Caudal portion receives inputs from other visceral afferents from CNs IX and X
Where do the somatic sensory fibers of the facial nerve project?
Spinal trigeminal nucleus
What is the pathway of the corneal reflex?
Afferents in CN V project to the chief sensory and spinal trigeminal nuclei
This input is projected bilaterally to both facial nuclei so the normal reflex is direct and consensual
What is the main sign for CN VII injury?
Face weakness
Although it can include a wide range of consequences reflecting the function of the facial nerve
What are the vestibulochoclear nuclei and what is their location?
Superior, medial, lateral, and inferior
Dorsolateral area of the caudal pons and rostral medulla, just medial to the inferior cerebellar peduncle.
What are the four components of the glossopharyngeal nerve?
Branchial motor component
Preganglionic parasympathetic component (parotid)
Somatic sensory
Visceral sensory (carotid, taste)
What is the nucleus ambiguus?
Located in the rostral medulla, dorsal to the inferior olive
Contains LMNs that innervate the stylopharyngeus muscle and LMNs for the brachial motor component of the vagus
What is the inferior salivatory nucleus?
Origin of the preganglionic parasympathetic fibers of CN IX
Caudal to the superior salivary nucleus
Where do the somatic sensor afferents in the glosspharygneal nerve project?
Trigeminal nucleus
Where do the visceral and chemical sensory afferents in the glossopharyngeal nerve project?
Solitary nucleus
What are the four functional components of CN X?
Banchial motor
Parasympathetic
Somatic sensory
Visceral sensory
What is the dorsal motor nucleus of the vagus?
Contains cell bodies of the origin for parasympathetic neurons of the vagus
Extends from rostral to caudal medulla
Receives sensory input from the solitary nucleus
Where do the somatic sensory afferents in the vagus project?
To the spinal trigeminal nucelus
Where do the visceral and chemical sensory afferent fibers of the vagus project?
Solitary nucleus
What is the result of a unilateral lesion to the nucleus ambiguus?
Ipsilateral paralysis of the soft palate, pharynx and larynx
Diminished gag reflex
Dyspnea, dysphagia, dysphonia
What is the function of CN XI?
Branchial motor innervation to the trapezius and SCM
What results from a lesion to CN XI?
Paralysis of the ipsilateral SCM and trapezius
Patient unable to turn their head away from the side of the lesion
What is the function of CN XII?
Innervates the intrinsic and extrinsic muscles of the tongue
Where is the hypoglossal nucleus?
Runs from rostral to caudal medulla and lies adjacent to the dorsal motor nucleus of the vagus
