PCOM: ONE 1 - week 5, Cranial Nerves V, and VII through XII

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The largest cranial nerve

CN V - Trigeminal

functions of CN V, Trigeminal

sensory:
- main sensory nerve for the face
- carris touch, temp, and pain
motor:
- innervates the muscles of mastication (temporalis, lateral pterygoid, medial pterygoid, masseter)

the muscles of mastication and the CN nerves that supply them

- temporalis - CN V
- lateral (external) pterygoid - CN V
- medial (internal) pterygoid - CN V
- masseter - CN V
- buccinator - CN VII

pathway and divisions of CN V, Trigeminal

CN V nerve fiber run from the pons to the face; three divisions:
V1 = opthalmic (S)
V2 = maxillary (S)
V3 = mandibular (B)

extremely painful pathology of CN V

trigeminal neuralgia

cause of trigeminal neuralgia

inflammation of CN V

S&S of trigeminal neuralgia

- excruciating pain (some of the worst known)
- stabbing pain that last from a few seconds to a minute
- pain may reoccur 100 times/day
- sensory stimulus triggers may include: light touch such as a breeze on the face

neurological test for CN V

the face brush test
- practitioner demonstrates the feel of a cotton ball by brushing it on the patent's sternum
- patient closes his eyes and the practitioner tests all three divisions bilaterally by randomly brushing the face with the cotton ball

the main motor nerve of the face

CN VII, the facial nerve

functions of CN VII, the facial nerve

- innervates the muscles of facial expression
- carries parasympathetic motor information to the lacrimal, palatine, and salivary glands
- carries sensory information (taste) to the anterior 2/3 of the tongue

pathway and branches of CN VII, the Facial nerve

CN VII nerve fibers run from the pons to the face with 5 branches...
Superior to inferior:
- temporal
- zygomatic
- buccal
- mandibular
- cervical

Bell's Palsy

a peripheral dysfunction of CN VII, the Facial Nerve (LMN disorder) caused by inflammation of the nerve

S&S of Bell's Palsy

- may develop rapidly (often overnight)
- involves paralysis of the facial muscles on the affected side
- may present with partial loss of taste (anterior 2/3 of tongue)
- lower eyelid droops
- corner of the mouth sags
- eye tears continuously
- difficulty closing the eye

CN VII Facial nerve impairment from stroke

- an UMN or central nerve palsy which does not affect the forehead

differential S&S of facial palsy from stoke and Bell's palsy

- both present with difficulty smiling
- stroke can wrinkle their forehead
- Bell's palsy will have difficulty wrinkling forehead

neurological test for CN VII, Facial Nerve

the smile and wrinkle forehead test:
- ask patient to smile and raise their eyebrows (to wrinkle their forehead)
- practitioner observes, looking for symmetry in the smile and the ability to wrinkle the forehead

functions of CN VIII, vestibulocochlear nerve

carries impulses for the senses of equilibrium and hearing

pathway of CN VIII, vestibulocochlear nerve, fibers and its branches

run from the inner ear to the pons:
- vestibular branch (equilibrium)
- cochlear branch (hearing)

what damage to CN VIII, vestibulocochlear nerve may cause

- deafness
- dizziness
- loss of balance
- nausea
- vomiting

neurological test for CN VIII vestibulocochlear nerve

fingertip moving test
- practitioner demonstrates the sound of his fingers rubbing together
- patient closes his eyes and is asked to tell the practitioner when he can no longer hear the sound of the fingers rubbing together
- practitioner rubs his fingers together and moves them laterally away until the sound is no longer heard by the patient
- practitioner observes for equidistant acuity bilaterally

functions of CN IX, glossopharyngeal nerve

motor:
- innervates part of the tongue and pharynx
- provides parasympathetic fibers to the parotid salivary glands
Sensory:
- conducts sensory information (including taste) from the pharynx
- conducts sensory information from the posterior 1/3 of the tongue

pathway of nerve fibers of CN IX glossopharyngeal nerve

CN IX, glossopharyngeal nerve fibers travel from the medulla to the throat

what damage to CN IX, the glossopharyngeal nerve may cause

damage to CN IX may impair swallowing and sense of taste

neurological test for CN IX, the glossopharyngeal nerve

CN IX is tested with CN X

alternate name for CN X, the Vagus nerve

the "vagabond" or the "wanderer"

distinctive characteristic of CN X the Vagus compared to all other cranial nerves

it is the only CN that extends beyond the head and neck

functions of CN X, the Vagus nerve

- motor supply to the pharynx and larynx to help with swallowing
- parasympathetic fibers regulate the heart, lungs, and abdominal viscera

pathway of CN X, the Vagus nerve

fibers run from the medulla through the neck, into the thorax and abdomen

what damage to CN X, the Vagus nerve can cause

- difficulty swallowing
- hoarseness or loss of voice

neurological test for CN IX & X, the Vagus and glossopharyngeal nerves

the "ah" test
- patient is asked to swallow and open his mouth and say "ah"
- practitioner watches for difficulty with any of these movements
- practitioner watches for the uvula to rise and listens for hoarseness

unique feature of CN XI, the accessory nerve

- formed from rootlets in the superior cervical spine
- it is the only CN that does not originate in the brain or brain stem

functions of CN XI, the accessory nerve

supplies motor function to the trapezius and SCM

pathway of CN XI the accessory nerve

CN XI nerve fibers run from the cervical spine along the spinal cord into the skull and then descend into the neck

what damage to CN XI the accessory nerve can cause

- the head may turn to one side
- there may be difficulty with shrugging shoulders

neurological test for CN XI the accessory nerve

the shoulder elevation test:
- patient is asked to elevate his shoulders
- patient is asked to resist downward pressure on his shoulders by the practitioner

functions of CN XII the hypoglossal nerve

carries motor function to the intrinsic and extrinsic muscles of the tongue

what damage to CN XII the hypoglossal nerve may cause

- difficulty with speech and swallowing
- difficulty extending tongue if damage is bilateral
- tongue will deviate if damage is unilateral

pathway of nerve fibers of CN XII the hypoglossal nerve

CN XII nerve fibers travel from the medulla to the tongue

neurological test for CN XII the hypoglossal nerve

stick out the tongue test:
- patient is asked to stick out his tongue
- practitioner observes for difficulty or deviation

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