CRANIAL NERVE REVIEW

1. I. OLFACTORY
• smell an alcohol swab
2. II. OPTIC
• Visual acuity: identify number of fingers or snellen chart
• Visual field: check peripheral vision
3. III. OCULOMOTOR
• Pupillary reaction: shine light into eye
• Accomodation: moving finger towards person's face - as pt is going cross-eyed pupils should constrict
• Maintaining open eyelid
• Looking Up & Inward (tested with IV and VI during EOM H-test [follow fingers with head still]) - Three to the trees
• Oculomotor nerve palsy causes "down 'n out" symptoms - lateral downward deviation of gaze
4. IV. TROCHLEAR NERVE
• Look down and inward eye movement: tested with III and VI during EOM H-test - Four to the floor
• Injury to CN IV may cause vertical diplopia (eg. during reading or walking downstairs) - double vision; affected eye will drift upward while looking down
5. V. TRIGEMINAL (3 branches V1 - ophthalmic, V2 - maxillary, V3 - mandibular)
• Facial sensation (afferent): touch both sides of forehead, cheeks and mandible for sensation symmetry
• Anterior tongue sensation (afferent)
• Corneal reflex sensory (afferent): drop of saline on cornea or touch with cotton swab
• Muscles of mastication (efferent): hold mouth open, bite down, move jaw side to side
6. VI. ABDUCENS
• Lateral eye movements (looking outward) - EOM H-test - Six to the sticks
7. VII. FACIAL (5 branches - Temporal, Zygomatic, Buccal, Marginal mandibular, Cervical - To zanzibar by motor car)
• Facial expression (efferent): smile, wrinkle face, puff cheeks, raise eyebrows
• Close eyelid (efferent): close eyes tightly
• Taste on anterior 2/3 of tongue
• Peripheral nerve stimulator applied to facial nerve contracts the obicularis oculi muscle to cause blinking
• Nerve palsy
• Peripheral (Bells) CN VII palsy/paralysis: usually viral or Lyme disease; will have ipsilateral weakness on entire face (upper and lower).  when asked to smile patient will be unable to open one eye fully and will have loss of cheek crease on same side.
• Central VII lesion: will have contralateral weakness only on lower half of face.  Eyelid will be normal but when asked to smile, pt will ahve loss of cheek crease on one side.  This is d/t the bilateral control of the upper facial muscles
8. VIII. ACOUSTIC aka VESTIBULO-COCHLEAR aka AUDITORY
• Hearing (cochlear): snap fingers by ear
• Weber test: tuning fork placed on top of head equi-distant from each ear
• Rinne test: tuning form placed on mastoid process then placed non-contact in front of ear
• Balance (vestibular): Romberg test: stand up, close eyes and stand still - loss of balance is positive test
• Cold caloric reflex test: tests vestibulo-ocular reflex by irrigating cold saline into external auditory canal; should see eyes turn toward ipsilateral ear with horizontal nystagmus to contralateral ear (opposite if using warm water).  May be used during brain death testing.
• Doll's Eye reflex test: head is turned side to side and eyes should move left or right to keep image in center of visual field (head turned to R, eyes will turn to L) to stabilize vision; during brain death eyes will stay fixed and will not move when head is turned side to side.
9. IX. GLOSSOPHARYNGEAL
• swallowing and voice: swallow; say "ahh"
• Sensory portion (afferent) of Gag reflex
• Sensory of posterior tongue
• Carotid body and carotid sinus afferents
10. X. VAGUS
• Motor portion (efferent) of gag reflex
• Parasympathetic innervation to many organs (slows heart rate, stimulates digestive organs, senses aortic blood pressure)
• motor control of larynx and pharynx
11. XI. SPINAL ACCESSORY
• Neck motion: shrug shoulders (trapezius); turn head side to side against clinician hand (SCM muscle)
12. XII. HYPOGLOSSAL
• tongue movement and strength: stick out tongue, move side to side (make sure it is midline)

QUESTION: Which CRANIAL NERVES are involved in the parasympathetic nervous system, or the "craniosacral" system?


ANSWER: cranial nerves 3, 7, 9 and 10
3, 7 and 9 preganglionic neurons comes off the brainstem to synapse at various ganglia, and the postganglionic neuron goes to the end organ (3 - eye muscle pupil constriction and near vision; 7 - lacrimal, nasal, submandibular, sublingual glands; 9 - parotid gland)
10 comes off the medula and branches come off the vagus and go to the end organ (heart, bronchial tree, stomach, intestines).  The postganglionic neuron is usually near or within the effector organ.
In addition to the cranial nerves, the craniosacral region also includes the pelvic splanchnic nerves of S2, S3, and S4 which go to the large intestine, bladder and male genitalia.


Common mnemonic for Cranial Nerves:
On Old Olympic Towering Tops A Finn And German Viewed Some Hops
Oh, Oh, Oh, To Touch And Feel A Girls Vagina And Hymen (for the pervs)

....or you can just memorize them ;)


If you can think of any anesthetic considerations for the Cranial nerves or board questions, please add them below.