week 2- cranial nerves Flashcards
CN I
what region of the brain does its nuclei reside
foramen it exits through
course within the brain
peripheral target
function
artery supply
how is it tested and interpretation
unique findings
what region of the brain does its nuclei reside: bipolar neurons in the nasal epithelium
foramen it exits through: cribiform plate
course within the brain: through cribiform plate to the olfactory bulb in the inferior and medial temporal lobe and then project to many places (see attached) including primative cortex and hippocampus
peripheral target: nose
function: smell
artery supply: Pterygopalatine of maxillary (3rd branch)
how is it tested and interpretation: test each seperately, use nasal spray and never ammonia
Unique: high turnover, oderant receptors, decreased is an early finding in neurodegenerative disorders
what type of neurons are the primary afferents that transmit special senses
bipolar
what are some reasons that someone would develop anosmia after a brain injury
- Coup-contrecoupcontusion/bruising of brain tissue
- Subdural hematoma due to tearing of bridging veins
- Shearing of bipolar axons!
what may olfactory hallucinations preceed
may be the aura preceding temporal lobe seizure (“uncinatefits”)
CN V
what region of the brain does its nuclei reside
foramen it exits through
course within the brain
peripheral target
function
artery supply
how is it tested and interpretation
unique findings
what region of the brain does its nuclei reside: trigeminal ganglion in midbrain for sensory and in the pons Masticator nucleus for motor
foramen it exits through: V1- superior orbital fissure, V2- foramen rotundum, V3- foramen ovale
course within the brain: all come in on trigem nerve and enter at the level of pons then seperates.
Spinal trigeminal- carries pain and temp give to nucleus in pons or medulla • send axons across midline to join spinothalamic tract and ascend to VPM of thalamus.
Light touch goes to main trigeminal or pontine nucleus
proprioception- only mandibular branch so V3- Mesencephalic Trigeminal Nucleus ( see next card for more details)
peripheral target: skin of face and masseter
function: V1 opthalmic - conjunctiva, cornea, forehead, eyelid, bridge of nose
V2 maxillary- cheeks, nasal cavity, upper jaw
V3 mandibular- lower jaw, teeth gums, anterior 2/3 of tongue,
plus external auditory meatus & tympanic membrane
motot- chewing
artery supply: basilar
how is it tested and interpretation: tissue sweep
motor-
•Push jaw laterally against resistance (pterygoidmuscles)
•Resist opening of jaw (masseter and temporalis muscles)
•Palpate masseter while patient bites down.
unique findings: if you bite your tongue you hurt V3
motor- since the nuclei are branchial, not somatic they are more anterior and lateral
•Cortical input to the Trigeminal Motor Nucleus is bilateral, so…a single UMN lesion has little effect (the contralateral UMN pool can still drive the LMNs.)
where are V Proprioceptive inputs are directed
Mesencephalic Trigeminal Nucleus
The Mesencephalic Nucleus contains the PRIMARY sensory neuron cell bodies (that we would have expected to find in the Trigeminal ganglion
Mesencephalic Nucleus projects to Trigeminal Motor Nucleus as the sensory arm of monosynaptic jaw jerk reflex arc
what would you suspect if a PT presented with unilateral weakness of bite
if left Trigeminal nerve were damaged, one would expect weakness of muscles on left side
how does the trigemmenal system handle
fine touch
temperature/pain
contralteral pain
proprioception
Fine touch: pontine trigemenal nucleus –> medial lameniscus –> VPM of thalmus
Pain:
enter at pons -> TRACTS –> Spinal Trigeminal nucleus (caudal pons and extends into spinal cord)–> midline to spinothalamic tract –> ascend to VPM of thalamus
contralateral side pain processing:
spinothalamic tract in the dorsal lateral medulla
proprioception:
only from mandibular tract –>Mesencephalic Trigeminal Nucleus contains the PRIMARY sensory neuron cell bodies (that we would have expectedto find in the Trigeminal ganglion) –> Trigeminal Motor Nucleus as the sensory arm of monosynaptic jaw jerk reflex arc
explain why upper motor neuron lesion may cause little weakness
Cortical input to the Trigeminal Motor Nucleus is bilateral, so…a single UMN lesion has little effect (the contralateral UMN pool can still drive the LMNs)
CN VII
what region of the brain does its nuclei reside
foramen it exits through
course within the brain
peripheral target
function
artery supply
how is it tested and interpretation
what region of the brain does its nuclei reside: facial nucleis is in dorsomedial pons (motor)
Superior Salivatory Nucleus in caudal dorsal pons (autonomic)
somatosensory and taste- Geniculate Ganglion
foramen it exits through:
course within the brain: exits brainstem laterally between pons & medulla
autonomic: sends its preganglionic parasymphathetic fibers to 2 nuclei, sphenopalatine for tearing, Submandibular ganglion for salivation
Taste:
geniculate ganglia –> Chorda Tympani –> intermediate nerve –> Nucleus of the Solitary Tract
somatosensory:
geniculate ganglia –> spinal trigemenal
peripheral target:
function: motor- facial expression and moves the ear to dampen loud noises
autonomic: tearing and salivation
taste: tongue
somatosen: ear and crude trouch
artery supply: basliar (paramedian branches since its more medial)
how is it tested and interpretation:
ask to smile, wrinkle forehead and puff cheeks
unique: •Wraps around Abducens Nucleus before exiting brainstem
what is hyperacusis a sign of
Ipsilateral LMN lesion to CNVII
distinguish between an UMN and LMN facial nerve lesion
LMN lesion = paralysis of ipsilateral face
UMN- only paralysis of forehead
LMN-
CN VII gone, face cannot move:
- No forehead wrinkle.
- No eye closing.
- No grinning.
- End of story.
UMN
CN VII is intact, but there is UMN damage
•Cannot tell lower face to move
But the other hemisphere serves as a “back-up system” for the forehead
explain this
The nerve tracts affecting voluntary facial movement probably originate from the main motor cortex. Those affecting involuntary movement during emotion probably arise from the caudal cingulate motor cortex, a medial brain region with inputs from the limbic system
CN IX
what region of the brain does its nuclei reside
foramen it exits through
course within the brain
peripheral target
function
artery supply
how is it tested and interpretation
what region of the brain does its nuclei reside: dorsolateral medulla
motor: Nucleus Ambiguus in lateral medulla
autonomic: dosal medulla
foramen it exits through: Jugular foramen
course within the brain:
peripheral target:
motor: mouth
autonomic: parotid
sensory: tongue & back of throat
function:
motor: speech (dysarthria) and swallowing (dysphagia) (elevates pharynx)
autonomic: salivation
sensory: taste, feeling on back of throat (GAG) and BP
artery supply: vetebral, posterior inferior cerebellar arteies
how is it tested and interpretation:
tongue depressor test, say ahh
unique: remember that it is branchial motor so will be more ventrolateral
As with most LMNs in the brainstem, these LMNs are driven by UMNs in the contralateral cortex, but also by a pool of UMNs in the ipsilateral motor cortex, so…UMN lesion usually has little effect
what is glossopharyngeal neuralgia and what nerve does it impact
CN IX
A rare nerve pain syndrome.
It is likely to be experienced as paroxysmal pain around the ear and in the back of the throat, iein the distribution of CN IX, that might be triggered by swallowing or speaking. Sometimes it proves to be a neuropathic pain (due to direct damage to the nerve) related to close proximity to a major vessel (e.g. PICA), in which case microvascular decompression surgery might be tried if medication fails to treat the pain
summarize the positioning of the motor and sensory and in brainstem including somatic, visceral and brachial motor
Branchial- all other muscles innervated by cranial nerves
Somatic- III,IV,VI, XII
Any muscle that’s not eyes or tongue then its innervated by branchial
describe the 3 different shapes of neurons
