Norden- Cranial Nerves Flashcards
Accomodation reflex / near triad
Controlled by cortex via connections w/ CN III
Increase in curvature of the lens (ciliary muscles)
Pupillary constriction (pupillary sphincter)
Convergence of eyes (medial rectus)
Frontal eye fields
Area 8
Frontal eye fields (area 8) provides innervation to which motor nuclei?
CN III, IV, VI
A lesion in the cortical area 8 will cause what?
Inability to voluntarily conjugately move eyes to the contralateral side of the lesion and there will be baseline bilateral eye deviation to the side of the lesion.
Direct the eyes to a new point of fixation
Gaze centers
Voluntary eye movements are initiated primarily in _
Areas 4 and 8
Where is the vertical gaze center located?
In the periaqueductal gray region of the midbrain reticular formation
Where is the horizontal gaze center?
Paramedian pontine reticular formation
The horizontal and vertical gaze centers have connections to CNs III, IV, and VI through ______
The medial longitudinal fasciculus
The medial longitudinal fasciculus major function is:
To coordinate eye movements
Involuntary jerking or oscillatory movement of the eyes: can be vertical, horizontal, or rotational
Nystagmus
Pathological nystagmus can be caused by lesions:
In medial longitudinal fasciculus, vestibular system, or cerebellum
Palsy
Weakness (paresis)
PERRLA
Pupils equal, round, reactive to both light and accomodation
Mydriasis
Sympathetic
Pupillary constriction (Miosis)
Parasympathetic
Interruption of parasympathetics in eye
Produces dilation bc of unnopposed sympathetic innervation
Interruption of sympathetic fibers of eye
Produces pupillary constriction (unopposed parasympathetic innervation)
The inability to move both eyes so that the image of an object falls on both foveas
Strabismus
Strabismus causes
Diplopia, bc each eye is seeing a slightly different image
What allows the retinal image to remain stationary when you turn your head?
Cycloduction done by inferior and superior oblique
LMN for Cranial nerves are where?
In the motor nuclei of CN’s throughout the brainstem
Projections of LMN to specific muscles (in Cranial nerves) can be ___
Ipsilateral or contralateral
What is the general rule for the laterality of the cranial nerve innervations?
from cortex (UMN ) to CN nucleus is typically bilateral with slightly more coming from contralateral than from ipsilateral.
From the LMN, innervation to specific muscles is ipsilateral
Action; medial rectus
Adduction
Action ; lateral rectus
Abduction
Action superior rectus
Elevation
Intorsion
Adduction
Action; inferior rectus
Depression
Extorsion
Adduction
Action: inferior rectus
Depression
Extorsion
Adduction
Action: superior oblique
Intorsion
Depression
Abduction
Action: inferior oblique
Extorsion
Elevation
Abduction
Edinger-estphal nuclues
CN III
Lacrimal and superior salivatory nuclei
CN VII
Nucleus for parasympathetics of CN III
Edinger-Westphal nucleus
Parasympathetic nuclei for CN VII
Lacrimal and superior salivatory nuclei
Parasympathetic nucleus for IX
Inferior salivatory nucleus
Parasympathetic nucleus for CN X
Dorsal motor nucleus
The alar plate of the closed neural tube differentiates into
Sensory components
The basal plate of the closed neural tube
Motor efferent components of cranial nerves
Motor nuclei lie ______ to sensory nuclei in the rhomboid fossa
Medial
Special sensory afferents are located most _____
Laterally
Spinal ganglia and nerves derived from
Neural crest
Autonomic ganglia, including parasympathetic ganglia in the head are derived from ?
Neural crest
Special sensory afferents are most ____ located
Laterally
General somatic efferents are most ____ located
Medially
Areas in the brain involved with olfaction
Rhinencephalon
The rhinencephalon is close in association with ______. Which causes certain smells to evoke memories and emotions
Limbic system
Lose sense of smell:
Anosmia
Anosmia can lead to what in elderly?
Weight loss, because food all tastes the same / bland
Olfactory neurons undergo ____ throughout life
Mitosis
Life span of olfactory neurons
2 months
Unusual characteristics in the olfactory system:
Olfactory neurons undergo mitosis throughout life. Regenerating olfactory neuron axons are able to grow into the hostile territory of the CNS.
Olfactory bulb axons are ensheathed in olfactory ensheathing cells (which are specialized glial cells).
[these have been used to promote nerve regen in spinal cord injury]
Input to the primary olfactory cortex, which is in the uncus and adjacent area of the parahippocampal gyrus (pyriform cortex) does what unique thing?
It does NOT relay through the thalamus
Pyriform cortex
Primary olfactory cortex
Temporal structures in olfaction:
Uncus and adjacent areas of the parahippocampal gyrus (pyriform cortex [primary olfactory cortex])
Entorhinal cortex (area 28)
Amygdaloid nuclear complex
Integrates information across multiple sensory modalities and projects to the hippocampus.
First cortical area to show degeneration in Alzheimer’s disease
Area 28 (entorhinal cortex)
Plays a critical role in both learned and unlearned (instictual) responses and memory
Amygdaloid nuclear complex
Medial olfactory area is where?
Frontal lobe
Why is important to not use ammonia when testing olfactory sense?
Ammonia stimulates pain fibers from CN V. So you wont’ actually test CN I
What is important to keep in mind when testing olfactory sense?
Make sure changes arent from obstruction of nasal passages
Note that some decreased sense of smell is NORMAL in elderly.
Don’t use ammonia
What is common in seizures induced by lesions in the uncus / amygdaloid?
Disagreeable odors
Stereotypic movements of the lips and tongue
Altered emotional state (anxiety / fear )
Automatisms
Stereotypic movements of the lips and tongue
Space occupying lesions where may cause unilateral anosmia?
The floor of the anterior cranial fossa
The frontal lobe
Near the optic chiasm/tract/nerve area
What can happen from fractures of the cribiform plate / ethmoid sinus ?
Tear fibers of olfactory nerve —> anosmia
Leakage of CSF from nose
Risk of meningitis and/or encephalitis
Is the nucleus for levator palpebrae superioris paired or unpaired?
Unpaired
Paired nucleus
Parasympathetic input to ciliary ganglion.
Part of accomodation reflex and pupillary light reflex
Edinger-Westphal nucleus
What can be used to independently evaluate the integrity of CN III?
Accommodation reflex, which projects directly to the Edinger-Westphal nucleus
What cranial nerves does the pupillary light reflex test?
CN II
CN III
What must you make sure to do when testing the pupillary light reflex for cranial nerves II (afferent) and III (efferent)
Separately test each eye for both direct and consensual response
Constriction of the pupil the light is not shined in in the pupillary light reflex?
Consensual response
Clinically, when testing the CN III (occulomotor) what should you most commonly focus on?
Ipsilateral changes involving medial rectus (for EOM damage), the eyelid, and the pupil (parasympathetic)
What should you look for in CN III damage?
Lateral strabismus (unopposed action of lateral rectus bc medial rectus is gone)
Ptosis
Mydriasis (unopposed action of dilator pupillae (sympathetic))
[no constriction to light OR accomodation]
Symptoms of oculomotor opthalmoplegia
Wrinkled forehead
Raised eyebrow
Lid droop
Downward abducted eye
Dilated pupil
What causes oculomotor opthalmoplegia?
Unilateral LMN lesion of CN III
All signs/symptoms are ipsilateral to lesion
Causes contralateral difficulty in depressing and intorting the eye
Unilateral lesions of trochlear nucleus and initial segment of the nerve in the midbrain
Patient’s w/ lesions involving trochlear nucleus or nerve will have ____
Vertical diplopia
Compensate by tilting head
Cell bodies of the primary sensory neurons of the trigeminal nerve are where?
Trigeminal (semilunar) ganglion
Mesencephalic nucleus
Which branch of cranial nerve V contains peripheral processes with origin in BOTH trigeminal ganglion and mesencephalic nucleus?
Mandibular nerve (sensory portion)
External ear sensory innervation:
VII, IX, X, V,
Second and third cervical nerves
Chief sensory nucleus carries what type of information?
Discriminative touch, vibration, conscious proprioception
The spinal trigeminal nucleus carries
Pain and temperature
The spinal trigeminal nucleus starts in the pons and then descends into the brainstem to the medulla, where it is continuous with __
The dorsolateral fasciculus of lissauer and the nuclei of the dorsal gray matter of the spinal cord
Projection to the reticular formation is important for _____ in response to pain
Arousal
Mesencephalic nucleus has neurons that are the only ______ primary sensory neurons found w/in the CNS
Pseudounipolar
Mesencephalic nucleus has proprioceptive receptors where?
Adjacent to teeth of the lower jaw and in neuromuscular spindles in the muscles of mastication, hard palate, adjacent to teeth of upper jaw
What does the mesencephalic nucleus sense?
Unconscious proprioceptive information
Information for the reflex control of bite comes from what nucleus?
Mesencephalic nucleus
What does the jaw jerk reflex test?
Sensory V (mesencephalic nucleus)
Motor V
What does the corneal reflex test?
Sensory (V1)
Motor (VII)
The trigeminal thalamic tract is a combination of the chief sensory neurons and the spinal trigeminal tract that starts at the thalamus. What senses does it carry?
Fine touch, proprioception, vibration, pain, and temperature for the face
What symptoms do you get in a lesion of the TTT above the level of the chief sensory nucleus?
In face
Contralateral
Loss of pain and temperature and fine touch, cons proprioception, vibration
Nucleus that receives synapse from VIII and then projects to the part of motor nucleus of V that innervates tensor tympani
Superior olivary nucleus (SON)
Characterized by excruciating paroxysms of sharp, stabbing pain in the area of distribution of one of the branches of CN V. Usually unilateral. May have remissions and exacerbations
Tic douloureux
Trigeminal neuralgia
What complication of shingles involving CN V must you worry about?
Ulcerations on the cornea which can cause blindness
The abducens nerve contains a subnucleus which is involved in what?
Conjugate horizontal eye movement
Fibers of the ___ nerve course medially and then dorsally over the abducens nucleus in the dorsal pons, forming a bulge
VII
VI palsy due to ICP / meningitis is a _____ because the primary lesion is not due to VI nerve or nucleus damage.
False localizing sign
What kind of diplopia is there in VI palsy?
Horizontal?
Why is it important to try to tell if a VI palsy is a real VI nerve palsy or a false localizing sign?
If it is a real VI nerve palsy, it can be life-threatening, bc that means there is a space-occupying lesion or vascular accident in the pons.
Cranial Nerve VII sensory components innervate what?
Cutaneous fibers to part of the external ear
Taste
Where are the cell bodies of origin for sensory Cranial nerve VII’s taste omponent
Geniculate ganglion
Area 43
Tast
Where is the motor Nucleus of VII?
Caudal part of pons
Cells for the parasympathetic part of CN VII are ???
The superior salivatory nucleus
Located in the pons
Lesions of the lower motor neurons of CN VII cause ?
Ipsilateral paralysis of all facial muscles
UMN lesion in area of CN VII what is symptom?
Contralateral paralysis of LOWER muscles of facial expression
Efferent components of CNs IX and X for innervation of muscles arise from
The nucleus ambigus
The nucleus ambiguus is a column of motor neurons situated _____
Dorsal to the inferior olivary nucleus in the medulla
Nucleus responsible for coughing, gagging and vomiting reflex?
Nucleus ambiguus
Stimulus for reflexes for coughing, gagging, and vomiting?
Stimuli arising in the mucosa of the respiratory and alimentary passages
Motor components of CNs IX and X arise from ?
Nucleus ambiguus
Gag reflex tests?
Sensory IX (from soft palate, pharynx, posterior aspect of tongue)
Motor efferents - from neurons of nucleus ambiguus
Uvula reflex test?
Say ahh
Observe uvula
Unilateral lesion of nucleus ambiguus will cause deviation of uvula towards contralateral side
A unilateral lesion of the nucleus ambiguus (LMN) causes
Ipsilateral paralysis of the soft palate, pharynx, and larynx
Pt will be hoarse, difficulty breathing, and swallowing. Gag reflex diminished/absent
Where is the spinal accessory nucleus (for CN XI)
Upper 5-6 cervical segments
Hypoglossal nucleus lies where?
Mostly medially in the medulla
The hypoglossal nucleus receives afferents from ?
Tractus solitarius (CN VII) [taste]
Sensory trigeminal nucleus (CN V)
[for reflex movements in swallowing and chewing]
Which muscle innervated by CN XII is the only that is contralateral from UMN?
Genioglossus
What are the other names for the chief sensory nucleus of V?
Principle, main, superior, pontine
What are the other names for the spinal nucleus of V?
Nucleus caudalis
LMN’s of CN III are where?
Midbrain
LMNs of CN IV are where
Midbrain
LMN’s of CN V are where?
Pons
LMN of CN VI are where?
Pons
LMN of CN VII are where?
Pons
LMN of CN IX are where?
Rostral medulla
LMN of CN X is where?
Rostral medulla
LMN of CN XII is where?
Caudal medulla
Where is the trochlear nucleus?
Medial midbrain at the level of the inferior colliculus
Where is the spinal nucleus of V (pain and temperatrue
From the pons (at level of chief nucleus) to caudal limit of medulla
Derived from neural crest. These are the only pseudounipolar cells found within the CNS
Mesencephalic nucleus
Mesencphalic neurons project mainly to the motor nucleus of V. Where is This nucleus??
In the pons at the same level as the chief sensory nucleus
By definition, the TTT (containing chief sensory nucleus of V and spinal trigemninal nucleus axons) is a ____ pathway
Crossed
The TTT synapses where?
VPM
At what level have all of the axons of the trigeminothalamic tract decussated?
Above the midpons
Above the chief sensory nucleus
The motor nucleus of V receives synapses from what nucleus, that end up being sent to the tensor tympani?
CN VIII fibers synapse in the superior olivary nucleus and then to the motor nucleus of V
Most frequently involved division in trigeminal neuralgia
Maxillary division
Where is the abducens nucleus?
Dorsal pons
Describe the course that is taken by fibers of CN VII for taste
Cell body of origin is in the geniculate ganglion. These take a long, peripheral course before synapsing in the rostral part of nucleus solitarius. Second order neurons then synapse in the thalamus at the VPM. From here, 3rd order neurons go to area 43 in the cortex (in postcentral gyrus)
Where is the motor nucleus of VII?
Caudal pons
Cells for the superior salivatory nucleus are where?
Scattered in the pons
Where is nucleus ambiguus (motor CN IX and X)
Dorsal to the inferior olivary nucleus in the medulla (cannot be see)
The dorsal motor nucleus of X does what?
Parasympathetic innervation
Majority end in adominal viscera
Where does the hypoglossal nucleus lie?
Most medially in the medulla between the dorsal nucleus of the vagus and the midline of the brain
The hypoglossal nucleus receives afferents from ?
Nucleus of tractus solitarius (CN VII)
Sensory Trigeminal Nuclei (CN V)
