12 cranial nerves
functionally similar to spinal nerves
Cranial nerves
- in brainstem
- innervate muscles of head, neck, face, larynx, tongue, pharynx, & glands
- Essential for speech, resonance, & phonation, swallowing, vagus
Optic nerve attachment to retina creates a ??
blind spot
CN I
olfactory nerve: sensation of smell
CN II
optic nerve: visual sensation
CNIII
oculomotor nerve: motor nerve, eyeball movement
CN IV
trochlear nerve: motor nerve, eyeball movement
CN V
trigeminal nerve: sensory (head, face, oral) and motor (jaw movement)
CN VI
abducens: motor nerve, eye movement through lateral rectus muscle
CN VII
facia: primarily motor, muscles of face, sensory-taste
CN VIII
vestibulocochear: sensory: equilibrium and hearing
CN IX
glossopharyngeal: motor (swallowing) and sensory (touch & taste from posterior third of tongue and pharynx)
CN X
Vagus: motor and sensory for pharynx, larynx, and soft palate
CN XI
spinal accessory: motor nerve
-muscles contolling head movement
CN XII hypoglossal nerve
motor nerve for muscles of tongue
Cranial nerve nuclei: midbrain 3 nuclei
- edinger-westphal nucleus
- oculomotor nucleus
- trochlear nucleu
Pons: 7 major nuclei
Trigeminal nerve, primary nucleus (spinal trigeminal and mesencephalic nuclei), abducens motor, and facial
Medulla: 9 major nuclei
- cochlear and vestibular nuclear complexes
- solitarius nucleus
- salivatory nucleus (ANS)
- hypoglossal nucleus
- ambiguus nucleus
- spinal trigeminal nucleus
Corticonuclear (bulbar fibers)
cortex to brainstem
Corticonuclear fibers
UMNs, LMNs
-Descend through internal capsule-genu
Sensory Pathways
three-order nuclei & fibers (moving from lower to upper)
first-order fibers
outside the CNS (tickle on the face)
Second-order fibers
brainstem gray matter: ducussating second-order fibers (right cheek tickle meets up w/ left cheek thalamus and crosses)
Third-order fibers
projections from the thalamus to the sensory cortex
UMNs
syndromes affect nerves from cortex to brainstem
LMNs
brainstem to face
3 sensory pathways (first, seond, third) and how many motor?
2: UMN and LMN
Complex Motor Innervation/Bilateral corticonuclear innervation
facial, trigeminal, vagus, glossopharyngeal
Complex/BilateralFacial innervates
upper face
Trigeminal innervates
masticators
Vagus innervates
pharynx & larynx
Glossopharyngeal innervates
pharynx
Unilateral corticonuclear innervation
facial, spinal accessory, hypoglossal, ocular muscles (oculomotor, trochlear, abdusence)
Unilateral facial innervates
lower facial muscles
Spinal accessory innervates
Sternocleidomastoid and trapezius muscles
Hypoglossal innervates
lingual muscles
oculomotor, trochlear, and abdusence innervate
ocular muscles
Conjugate gaze center
cortinoculear projections for the coordination of both eyes
Trigeminal nerve Function
sensory- face, head, oral, orbital cavities
motor-muscles of mastication/chewing
Trigeminal nerve structures/complex
- primary sensory nucleus
- spinal nucleus
- mesencephalic nucleus
Sensory portion of trigeminal nerve
- thalamic
- maxillary
- mandibular
2nd order neurons of trigeminal
- principle trigeminal nucleus
- mesencephalic
- spinal trigeminal
principle trigeminal nucleus
TOUCH
- most cross contralateral thalamuc nucleus
- some sensory info from teeth and jaws goes to thalamus
mesencephalic
PROPRIOCEPTION
-bilateral: biting, chewing, swallowing are all symmetrical
spinal trigeminal
PAIN
-contralateral thalamus
Clinical probs w/ Trigeminal Nerve
- Trigeminal neuralgia
- Peripheral branch damage
- Special Visceral (Branchial) Efferent
- Motor Nucleus damage
- Unilateral cortical or corticonuclear injury
- Bilateral cortical (UMN) or LMN lesion
Trigeminal neuralgia
tic douloureux-chronic pain sensation of unknown etiology
Sensation/touch damage to Peripheral branch
Ipsilateral loss of sensation-face, tongue, teeth, mouth, gum & cavities oral/orbital
Testing Peripheral branch damage
Stimuli of cotton, pin prick, & reflexes (sneeze & corneal)
Special Visceral (Branchial) Efferent/ damage to Trigeminal
motor nucleus, masticators, Tensor veli palatini (preventing food from nasopharynx) and tensor tympani (restricting malleus motion on exposure to loud sound)
Motor nucleus damage/ Trigeminal nerve
LMN syndrome: paralysis of ipsilateral masticators w/ jaw deviation to site of injury: deviation obvious upon jaw protrusion
-muscles twitch, gradually atrophy, and jerk/reflex absent
Unilateral cortical or corticonuclear injury has mild effect on jaw strength/trigeminal nerve
due to bilatera innervation
Bilateral control (UMN) or LMN lesion/Trigeminal nerve damage
bilateral jaw paralysis
Testing trigeminal nerve damage for motor damage
lateral & frontal jaw movement against resistance, also can be test phones requiring jaw support (bilapials, labiodental, dentals, and palatals)
Facial Nerve Function
Motor: muscles of face, scalp & stapeius: kissing, blowing, speaking, smiling, raising, eyebrows, emotional expressions, and swallowing
Facial Nerve Function #2
Superior salivatory: paraysympathetic efferent to lacrimal, sublingual & submandibular glands & secretory glands in mouth & nasal cavities
Facial Nerve function #3
Sensory: Nucleus Solitarius: Taste sensation: anterior 2/3 of the tongue
Facial Innervation: corticobulbar
- lower face
2. upper face
Frontal Innervation: lower face
contralateral innervation
Frontal innervation: upper face
bilateral innervation
Clinical Implications w/ UMN
paralysis in contralateral lower half of face w/ spared upper face
Clinical implications w/ LMN or bilateral cortical lesion:
paralysis of upper & lower face
Clinical correlates w/ Facial Nerve damage #1:
Pons-affect all 3 (general visceral efferent, special visceral afferent, and special visual efferent) functions
Clinical correlates w/ Facial Nerve damage #2:
Facial nerve beyond stylomastoid forament: paralysis of ipsilateral half of facial muscles, intact glandular secretion & taste sensation
Clinical correlates w/ Facial Nerve damage #3:
General Visceral Efferent fibers: secretory dysfunctions of glands in eye & palate
Clinical correlates w/ Facial Nerve Damage #4:
Interruption of efferents to middle ear-hyperacusia (normal sounds seem louder)
Bells Palsy: facial nerve dysfunction
Lower Motor Neuron Syndrome: sudden onset of paralysis of ipsilateral upper and lower facial muscles
Bells Palsy etiology
nerve degeneration, inflammation or infection of facial nerve
Testing facial nerve damage by asking patient to
smile, part lips, show teeth, puff out cheeks, pucker lips, express emotions
-taste eval: salt, sugar, vinegar
Vestibulochoclear Nerve Function
equilibrium and audition
Vestibular nerve Fx: Special Somatic Afferent
maintains equilibrium, coordination of head and body, stabilization of visual fixation point during movement
first order vestibular
superior & inferior vestibular ganglia
second order vestibular
nuclei in caudal pons
projections to ???/vestibular
MLF/ocular fixation & cerebellum/equilibrium
Scarpas ganglion
nucleus for vestibular nerve/first order
Auditory nerve
bilateral projections to cortex and tonotopic representation throughout path and auditory cortex-equally important descending fibers
First order auditory nerve
spiral ganglia
second order auditory nerve
cochlear nuclei in caudal pons
3rd order is always the same: always goes to motor cortex!
ALWAYS GOES TO MOTOR
Clinical correlates of vestbulacochlear nerve
equilibrium and audition
Equillibrium of vestibulacoch
disturbances of equilibrium and impaired vertigo/dizziness
Audition of vestibulocohelaer
conductive or sensorineural hearing loss, brainstem lesion-partial impariment (bilateral projections)
Glossopharyngeal nerve function
functionally identical to vagus nerve
Sensorimotor nucleus of glossopharyngeal nerve
- inferior salivatory nucleus
- nucleus ambiguus
- nucleus solitarius
glossopharyngeal and vagus share a ?
ganglion-functionally same
glossopharyngeal first order
inferior ganglion
glossopharyngeal second order
nucleus solitarius
glossopharyngeal
VPM of thalamus
General Visceral Afferent of Glossopharyngeal
inputs from carotid body (chemoreceptors) in response to changes in blood carbon dioxide help control respiration rate
-carotid sinus baroreceptors respond to increased blood pressure and control blood flow
- Nucleus Solitarius of glossopharyngeal
taste sensation from posterior third of tongue and oral pharynx
- Inferior Salivatory Nucleus of glossopharyngeal
controls glands and cardiac muscles, regulates secretion from parotid gland and secretion from oral pharynx
- preganglionic parasympathetic projections to inferior salivatory nucleus
- postganglionic projections to otic ganglion (parotid secretion)
- Nucleus Ambiguus (branchial branch) of glossopharyngeal
nucleus ambiguus is rostral, bilaterally innervated, and regulates swallowing by projections to (ipsilateral stylopharyngeal muscle, upper pharyngeal constrictor fibers)
Clinical correlates to glossopharyngeal
- discrete lesion
- loss of taste
- loss of gag reflex
- excessive oral secretion
discrete lesion of glossopharyngeal
partial paresis of unilateral stylopharyngeal muscle (impairment of ipsilateral pharyngeal elevation in deglutition)