Cranial Nerve I

Olfactory nerve

(Sensory) 

function

- Smell

clinical test

- Present the patient with familiar, non-irritating odors (one nostril at a time, with eyes closed). Ask them if they smell anything, and if so, can they identify what they smell.

Cranial Nerve II

Optic nerve

(Sensory) 

function

- Vision

clinical tests

1) Test visual acuity

       - with an eye chart, wearing contacts/glasses

2) Test the visual fields by confrontation

       - bilateral simultaneous finger-wiggling test

3) Inspect the optic fundi with an opthalmoscope

4) Inspect size, shape, & symmetry of pupils. Test

    pupillary reactions to light & near effort (also

    tests CNIII).

       - may also do swinging light test - Marcus

         Gunn pupil indicates damage to CNII (not

         CNIII)

Cranial Nerve III

Occulomotor nerve

(Motor)

functions: 

1) Eye movement

     - inferior, medial & superior rectus, & inferior

       oblique

2) Opening of eyelid

      - levator palpebrae superioris

3) Focusing (accommodation) of lens

      - ciliary muscle

4) Pupil constriction

      - constrictor papillae muscle

clinical tests

1) Test extra-ocular movements* (also tests CN4,6)

       - Straight-ahead corneal reflections

       - Six cardinal directions with wide H

       - Convergence

2) Look for ptosis (drooping) of either eyelid

3) Inspect size, shape, & symmetry of pupils. Test

    pupillary reactions to light & near effort (also

    tests CN2).

*CN 3 injury affects the inferior, superior, & medial rectus, and the inferior oblique:

      - When looking straight ahead, affected eye

        deviates laterally

      - Upward, downward, & medial movements of

        affected eye are impaired

[image]

Cranial Nerve IV

Trochlear nerve

(Motor)

function: 

1) Eye movement

       - superior oblique (downward movement while

         looking inward)

clinical tests:

1) Test extra-ocular movements* (also tests CN3,6)

       - Straight-ahead corneal reflections      

       - Six cardinal directions with wide H

       - Convergence

* CN 4 injury affects the superior oblique muscle

      - Affected eye cannot look down while looking

        medially

[image]

Cranial Nerve V

Trigeminal nerve

(Mixed)

functions:

1) Sensation from scalp, face, cornea &

     conunctiva, teeth, anterior tongue, oral &

     nasal mucosa

2) Chewing (also swallowing & speech)

       - Muscles of mastication (masseter,

         temporalis, medial & lateral pterygoid)

       - Tensor veli palatini, tensor tympani

       - Mylohyoid & anterior belly of the digastric

clinical tests:

1) Test for pain/temp. & light touch sensation

       - Pain: object with sharp & dull ends

       - Touch: wisp of cotton

2) Test the corneal reflex

       - Wisp of cotton to the cornea, should blink

3) Test the strength of muscles of mastication

       - palpate temporal & masseter while clenching

Cranial Nerve VI

Abducens nerve

(Motor)

function: 

1) Eye movement

      - Lateral rectus (lateral gaze)

clinical tests:

1) Test extra-ocular movements* (also tests CN3,4)

       - Straight-ahead corneal reflections      

       - Six cardinal directions with wide H

       - Convergence

* CN 6 injury affects the lateral rectus muscle

       - When looking straight ahead, affected eye

         deviates medially

       - Affected eye cannot look laterally

[image]

Cranial Nerve VII

Facial nerve

(Mixed)

functions: 

1) Facial expression

2) Taste from anterior tongue

3) Sensation from skin of concha & behind ear

4) Salivation

       - submandibular & sublingual glands

5) Crying

       - lacrimal gland

clinical tests:

1) Test muscles of facial expression

      - Raise eyebrows, frown, close eyes against

        resistance, show teeth, smile, puff cheeks

Cranial Nerve VIII

Vestibulocochlear nerve

(sensory)

functions: 

1) Hearing

2) Regulation of posture, balance, equilibrium

       - By conveying info about position of head

         from the vestibular system

clinical tests:

1) Assess hearing

       - Whisper or finger-rub test

       - If a problem appears, do the Weber (tuning

         fork on top of head) and Rinne (tuning fork

         on mastoid bone) tests

Cranial Nerve IX

Glossopharyngeal nerve

(Mixed)

functions: 

1) Swallowing (& speech)

       - stylopharyngeus muscle

2) Salivation

        - parotid gland

3) Taste from posterior tongue

4) Sensation from pharynx, throat, & posterior

    tongue (sensory part of the gag reflex) & parts

    of the ear.

5) Regulation of blood pressure and O2 sat

       - baro- and chemo-receptors of carotid sinus

clinical tests:

1) Ask the patient to swallow (also tests CN 10)

2) Test the gag reflex (also tests CN 10)

Cranial Nerve X

Vagus nerve

(Mixed)

functions:

1) Swallowing, speech, gag-reflex

       - Some muscles of the pharynx, larynx, &

         tongue (palatoglossus only)

2) Motor innervation (parasympathetic) of

    thoracic and abdominal viscera.

       - Slows HR

       - Increases pulmonary secretions

       - Stimulates bronchoconstriction

       - Increases GI secretions & motility

3) Sensory information from the

     thoracic & abdominal viscera

4) Sensation from some parts of ear & pharynx

5) Taste (from the epiglottic region only)

clinical tests:

1) Assess the patient's voice

       - hoarseness or nasal quality

2) Ask the patient to swallow (also tests CN 9)

3) Assess movements of the palate & pharynx

       - "Ahhh" test

4) Test the gag reflex (also tests CN 9)

Cranial Nerve XI

Accessory nerve

(Motor)

functions:

1) Movements of head & neck

      - trapezius & sternocleidomastoid

2) (Swallowing - may be considered part of vagus)

clinical tests:

1) Visually inspect trapezius

       - atrophy, fasciculations, symmetry

2) Assess trapezius strength

       - shoulder shrug against resistance

3) Assess sternocleidomastoid strength

       - Turn head agains resistance

Cranial Nerve XII

Hypoglossal nerve

(Motor)

functions:

1) Movement of tongue (speech, chewing, swallowing)

       - all intrinsic muscles & all but one extrinsic

         muscle of the tongue

clinical tests:

1) Listen to the articulation of patient's speech

   (also tests CN 5, 7, and 10)

2) Inspect the tongue

       - both inside the mouth & protruded

3) Assess strength of tongue muscles

       - move side to side, possibly move against

         cheek

Smell

Olfactory nerve (CN 1)

Vision

Optic nerve (CN 2)

Hearing

Vestibulocochlear nerve (CN 8)

Taste

Facial nerve (CN 7)       

       - Taste from anterior 2/3 of tongue

Glossopharyngeal (CN 9)         

       - Taste from posterior 1/3 of tongue

[Vagus (CN 10) – VERY minor contribution]         

       - Taste from epiglottic region

Movements of the eyes & eye-lids

Occulomotor nerve (CN 3)

       - 4 of 6 extraocular muscles: superior,

        inferior,and medial rectus, inferior oblique

      - Opening of eyelid

         (levator palpebrae superioris)

      - Constriction of pupil

         (constrictor papillae muscle)

       - Accomodation of lens 

         (ciliary muscle)

Trochlear nerve (CN 4)

      - Superior oblique muscle (downward gaze

        while eye is turned medially)

Abducens nerve (CN 6)

       - Lateral rectus muscle (lateral gaze)

Facial nerve (CN 7)

       - Orbicularis oculi, closing of eyes

[image]

Crying

Facial nerve (CN 7)

       - Lacrimal glands

Movements of facial expression

Facial nerve (CN 7)

Sensation from the face

Trigeminal nerve (CN 5)

Sensation from the ear

& surrounding area

Facial nerve (CN 7)

       - Skin of concha & area just behind the ear

Glossopharyngeal nerve (CN 9)

      - Skin of the external ear, parts of the

        tympanic membrane

Vagus (CN 10)

       - Skin of the back of the ear, external auditory

Movements of chewing,

swallowing, & speech

Trigeminal nerve (CN 5)

       - Muscles of mastication: masseter, temporalis,

        medial pterygoid, lateral pterygoid

      - Tensor veli palatini, mylohyoid, anterior belly

        of the digastric muscle

Facial nerve (CN 7)

       - E.g., buccinator, orbicularis oris, involved in 

        chewing & phonation

Glossopharyngeal nerve (CN 9)       

       - Stylopharyngeus, involved in swallowing

Vagus nerve (CN 10)

       - Some voluntary muscles of the pharynx &

        most of larynx (incl. vocal cords)

      - Palatoglossus muscle, one of the extrinsic

        muscles of the tongue

Hypoglossal nerve (CN 12)

       - All intrinsic and 3 of the 4 extrinsic muscles  

        of the tongue

Salivation

Facial nerve (CN 7)      

      - Submandibular & sublingual glands

Glossopharyngeal nerve (CN 9)         

       - Parotid gland

Sensation from inside the mouth

Trigeminal nerve (CN 5)         

       - Anterior tongue, teeth, oral mucosa

Glossopharyngeal (CN 9)

       - Posterior tongue

Sensation from pharynx & larynx

Glossopharyngeal (CN 9)      

       - pharynx & throat, sensory arm of gag-reflex

Vagus (CN 10)

       - Some somatic sensation from pharynx,    

         visceral sensation from larynx, trachea

Movements of head,

neck & shoulders

Accessory nerve (CN 11)       

       - Trapezius & sternocleidomastoid

Sensation from scalp

Trigeminal nerve (CN 5)

Maintenance of balance & equilibrium

Vestibulocochlear nerve (CN 8)       

       - Sensory afferents from vestibular apparatus

Regulation of blood pressure

& O2 saturation

Glossopharyngeal nerve (CN 9)      

       - Sensory afferents from carotid bodies

Vagus nerve (CN 10)

      - Sensory afferents from aortic arch & aortic

        bodies

Sensory & motor innervation of

thoracic & abdominal viscera

Vagus nerve (CN 10) (parasympathetic)

Gag reflex

Glossopharyngeal nerve (CN 9)

       - Conveys sensation from pharynx & posterior

        tongue

Vagus nerve (CN 10)

       - Provides motor innervations of pharynx,

        larynx, esophagus, & GI system

Corneal reflex

Trigeminal nerve (CN 5)       

      - Conveys sensation from cornea

Facial nerve (CN 7)         

       - Orbicularis oculi, closes eyes

Pupillary reflexes

Constriction in response to light & to focus on a near object

Optic nerve (CN 2)

       - Senses light, necessary for pupillary light

        reflex

Occulomotor nerve (CN 3)      

       - Constrictor papillae muscle, constricts pupil