Cranial Nerve Evaluation

• Here is a website with little videos showing how to test each cranial nerve.

• http://icarus.med.utoronto.ca/NeuroExam/

• Let’s look at an example

Other helps to learn cranial nerves

• http://rad.usuhs.mil/cranial_nerves/timrad.html – Provides a table with all twelve nerves,

descriptions, images, and pathology

There are ______pairs of cranial nerves and _______pairs of spinal nerves.

• A. 13 and 21• B. 21 and 13• C. 12 and 31• D. 31 and 12

Cranial Nerve I: Olfactory Nerve

Cranial Nerve II: Optic Nerve

Discuss III, IV, VIAnd then V

Test will cover through VI, but not V

Cranial Nerves III, IV, VI

See Kimberly Goodman in action

• http://emuse.ebaumsworld.com/video/watch/430

Eye simulator to help us learn

• http://rad.usuhs.mil/rad/eye_simulator/eyesim.htm

• You can choose the pathology, then see it in action

• There is a quiz mode too

Which nerve has been affected?

Deadly Nightshade (Atropa belladonna)

Use: Atropine

• Atropine competitively inhibits the action of acetylcholine (ACh) at the acetylcholine receptor in the nerve synapse, thereby preventing the parasympathetic nervous system from sending out electrical nerve impulses.

• Since the parasympathetic nervous system regulates non-volitional/subconscious activities (such as sweating, breathing, and heart rate) when it is prevented from sending out signals, the heartbeat and breathing become extremely irregular.

Why medieval Italian women used Belladonna

Patient told to look down and to the left. Which nervehas been affected?

Patient told to look to the right. What is wrong?

Which of the following cranial nerves contains chemoreceptors?

• a. Olfactory• b. Optic• c. Oculomotor• d. Trochlear• e. Trigeminal

Cranial Nerve V: Trigeminal

Ophthalmicnerve-Superiororbital fissure

Maxillarynerve-foramenRotundum

Mandibularnerve-foramenOvale

Mnemonic for where the nerves exit: Standing Room Only

Anesthesia given near the mandibular foramen blocks sensationin the lower jaw, the lower lip, chin, and tongue

• Lidocaine (usually used to numb small patch of skin) can be applied intranasally to give relief within 5 minutes from migraines and cluster headaches. Relief may only last about an hour.

Cranial Nerve VII: Facial

Bell’s palsy

• About 1 in 5,000 people affected

• About 50% of affected people recover in a short time. Another 35% will recover within a year.

• Herpes Simplex 1 is most likely cause

The maxillary branch of the fifth cranial nerve passes through the skull via the:

• a. superior orbita fissure• b. foramen rotundum• c. foramen ovale• d. foramen lacerum• e. jugular foramen

Cranial Nerve VIII: Vestibulocochlear

Cranial Nerve IX: Glossopharyngeal

Cranial Nerve X: Vagus

A vagabond

How would a member of the medical profession test a patient for damage to the vestibular branch of the vestibulocochlear nerve?

• a. test hearing with a tuning fork• b. examine disturbances with

swallowing and speech• c. check muscle motion when teeth are

clenched• d. ask the patient to walk a straight line

Cranial Nerve XI: Accessory

Cranial Nerve XII:

Hypoglossal

Which cranial nerves are involved in swallowing?

Glossopharyngeal (IX), Accessory (XI), Vagus (X), and Hypoglossal (XII)

NEW BOOK

The peripheral nervous system (PNS) is composed of cranial nerves and spinal nerves that relay information to and from the central nervous system (CNS).

Nerves can be sensory, motor, or mixed (sensory and motor)

Cranial nerves arise from the underside of the brain and are numbered with Roman numerals, starting anteriorly (I) and progressing posteriorly (XII)

Cranial nerve wrist watch

OLd OPie OCCasionally TRies TRIgonometry And Feels VEry GLoomy, VAGUe, Acutely HYPOactive

On Occasion Our Trusty Truck Acts Funny. Very Good Vehicle Any How. On Old Olympus' Towering Top A Finely Vested German Viewed A Hawk On Old Olympus' Towering Top A Finn And German Viewed Some Hops

(Note that the Vestibulocochlear nerve is referred to by its former name, Auditory, in this mnemonic.)

Oliver the optimistic octopus trots triumphantly about facing audiences glossily vaguely spinning hippos.

(Note that the accessory nerve is referred to by its alternate name Spinal accessory nerve, and the Vestibulocochlear

nerve by its former name, Auditory, in this mnemonic.) Orange orangutans often try to avoid feeding angry gorillas very ancient hotdogs. (Note that the Vestibulocochlear nerve is referred to by its former name, Auditory, in this

mnemonic.) (Note that the Vestibulocochlear nerve is referred to by its former name, Auditory, in this

mnemonic.) Oh Oh Oh To Touch And Feel Very Good Velvet, Ah Heaven

Oh, Oh, Oh, To Touch And Feel Very Good Velvet. Such Heaven! (Note that the accessory nerve is referred to by its alternate name Spinal accessory nerve in

this mnemonic.) Oh Once One Takes The Anatomy Final Very Good Vacations Are Heavenly

OOO Truely There Are Five Very Gorgeous Vixens Awaiting Him Oh, Oh, Onward Through The Airy Facade Viewing Gorgeous Vixens Accessorizing Hopelessly

There are MANY cranial nerve mnemonics on the internet!

Another to help remember the types of information these nerves carry (sensory, motor, or both) is thus:

Some Say Money Matters, But My Brother Says Big Brains Matter More.

Some Say Marry Money, But My Brother Says Bad Business Marry Money.

Some Say Marry Money, But My Brother Says Big Brains Matter More.

Some Say Marry Money, But My Brother Says Big Boobs Matter More.

Some Say Marry Money, But My Brother Says Big Butts Matter More.

Small Ships Make Money, But My Brother Says Big Boats Make More.

Some Say Marilyn Monroe, But My Brother Says Bridgette Bardot Mmmm Mmmmm.

There are MANY mnemonics to designate sensory, motor, or both

Cranial Nerve I: Olfactory Nerve

Olfactory nerve (cranial nerve I) is purely sensory and bypasses the thalamus. It is responsible for our sense of smell.

Cranial nerve I (olfactory nerve) relies upon chemoreceptors in upper nasal mucous membranes.

Locations in upper mucous membranes of the nasal cavity where chemoreceptors of olfactory nerve are located.

The paired olfactory bulbs and tracts are located above the cribriform plate and lateral to the crista galli

Note the subarachnoid space and note the delicate nerve fibers that pass from the olfactory bulb and tract through the cribriform plate. A severe fall on the back of the head could sever these delicate fibers.

Optic nerve (cranial nerve II) is purely sensory. It relays visual nerve impulses to the occipital lobes.

NORMALLY THE BLOOD-BRAIN BARRIER BLOCKS MOST DANGEROUS FOREIGN PARTICLES, SUCH AS PATHOGENS, FROM REACHING THE CENTRAL NERVOUS SYSTEM. HOWEVER, ACCORDING TO YOUR SUPPLEMENTAL READING, HOW CAN THIS PROTECTION BE BYPASSED, POTENTIALLY INCREASING OUR RISK OF TOXIC DISEASE?

A MIGRATION OF TOXIC MATERIALS DOWN HAIR SHAFTS AND FOLLICLESB MOVEMENT OF INGESTED MATERIALS VIA THE LYMPHATIC SYSTEMC MIGRATION OF INHALED PARTICLES WITHIN THE CYTOPLASM OF CRANIAL NERVE ID INWARD PROGRESSION FROM ORBIT ALONG OPTIC

NERVEE TRAUMA TO NASAL CONCHAE

Note that the optic chiasma is located immediately over the sella turcica and the pituitary gland

Note that some of the nerve fibers (from the medial portion of the retina) cross over at the optic chiasma and continue to the opposite occipital lobe

The medial portion of the retina is responsible for our temporal field of view while the lateral portion of our retina is responsible for our nasal field of view. So, it is the nerve fibers responsible for our temporal fields of view that cross in the central portion of the optic chiasma and continue on to the opposite occipital lobes.

Note the nerve tracts responsible for our temporal field of view cross in the central portion of the optic chiasm while the tracts for the nasal fields of view are in the outer portion of the optic chiasma and continue to the occipital lobe on that same side

The optic nerve tracts eventually go to the occipital lobes of the cerebrum

Coronal view of pituitary tumor rising superiorly from the sella turcica of the sphenoid bone. Such tumors can put pressure on the central portion of the optic chiasma where nerve fibers for the temporal field of view normally pass. Read the clinical view in the text.

Pressure on the central portion of the optic chiasma can impair vision for the temporal fields of view.

Dr. McCoyCaptain Kirk

Ensign Chekov

Whale expert

In Chekov's emergency room, a doctor buzzes up a drill. Bones examines Chekov while the Drill Doctor demands to know who he is, how he got in, and what the hell he's doing. "Tearing of the middle meningeal artery," Bones muses. "What's your degree in -- dentistry?" the Drill Doctor asks. "How do you explain slowing pulse, low respiratory rate, and coma?" Bones demands. "Funduscopic examination!" Dr. Drill announces. "Funduscopic examination is unrevealing in these cases!" Bones snaps back. "A simple evacuation of the expanding epidural hematoma will relieve the pressure!" Dr. Drill shouts. "My god man, drilling holes in his head is not the answer -- the artery must be repaired. Now, put away your butcher knives and let me save this patient before it's too late!" Bones pleads. Dr. Drill puts down his drill and says he's going to have them removed.

Quote from hospital room in Star Trek: The Voyage Home

Chekov suffered an epidural hematoma after a fall. This resulted in increased intracranial pressure and increased spinal fluid pressure. Healing device on forehead is applied by Dr. McCoy.

Note that the meninges and CSF travel along the optic nerve to the back of the eyeball.

Note subarachnoid space and CSF traveling to back of eyeball and optic disc (blind spot)

Close-up of subarachnoid space leading to optic disc.

The fundus (“the portion of a hollow organ furthest from its opening”) of the eyeball is the back of the eyeball. Funduscopic examination of the retina is being performed.

caused by increased spinal fluid pressure. The optic disc is bulging anteriorly

IF A SOLDIER HAD HIS RIGHT OCCIPTIAL LOBE DESTROYED BY SHRAPNEL FROM A ROADSIDE BOMB, WHAT FIELDS OF VISION WOULD HE LOSE?

A RIGHT NASAL AND RIGHT TEMPORAL

B RIGHT NASAL AND LEFT NASAL

C LEFT NASAL AND LEFT TEMPORAL

D LEFT TEMPORAL AND RIGHT NASAL

E LEFT TEMPORAL AND RIGHT TEMPORAL

The oculomotor nerve (cranial nerve III) controls certain extrinsic and intrinsic muscles of the eye.

The occulomotor nerve passes through the superior orbital fissure of the sphenoid bone

The occulomotor nerve (cranial nerve III) controls some muscles on the outside of the eye (extrinsic) and some muscles on the inside of the eye (intrinsic).

The oculomotor nerve can control movement of the eye, dilation and contraction of the iris (colored part of eye), and change the shape of the lens for fine focusing.

Pupil is hole in center of iris

Iris is colored part of the eye that can contract or relax

Pressure on the tentorial incisure (tentorial notch) can lead to inactivation of one, or both, oculomotor nerves.

Close-up of tentorial incisure (tentorial notch) where pressure can occur on one or both sides.

See previous slide for posterior communicating artery.

Defective oculomotor nerve. If pressure is on same side as nerve it is said to be “ipsilateral”

The trochlear nerve goes to a single muscle with a “pulley-like” arrangement to cause the eyeball to look downward

Close-up of “pulley-like” arrangement of muscle stimulated by the trochlear nerve that causes downward movement of the eye.

Can’t look down

The trigeminal nerve (cranial nerve V) has both motor and sensory functions in the face

The trigeminal nerve (cranial nerve V) has three divisions that serve defined regions of the face. Damage or disease to the branch in one division will lead to problems in that one division.

Shingles (reactivation of childhood chickenpox) can spread to the skin from one division of a nerve. In this case the first division (ophthalmic branch) of trigeminal nerve.

The photic sneeze reflex is apparently an inherited condition of cross-wiring between the optic nerve and the maxillary branch of the trigeminal nerve that leads to sneezing when a person is exposed to bright light.

Dental anesthesia is often done to temporarily deaden the second and third divisions of cranial nerve V.

The trigeminal nerve also has motor functions

The trigeminal nerve stimulates the muscles of mastication: masseter, temporalis, and medial/lateral pterygoids.

nerve V)

The abducens nerve (cranial nerve VI) stimulates a single muscle that causes the eye to move laterally

Abducens nerve in action with the right eye

The abducens nerve also passes near the tentorial incisure

Close-up of abducens nerve near the tentorial incisure (tentorial notch). Pressure on this nerve on the right side will lead to palsy (paralysis) of the eye muscle on the right side (ipsilateral)

The facial nerve has both motor and sensory functions in the face.

The motor functions of the facial nerve innervate the epicranius, buccinator, obicularis oris, and the platysma

The facial nerve stimulates glands and receives sensations of taste from front of the tongue.

When I checked the Internet, it seems that all four sensations of taste occur commonly through large areas of the tongue (there is some question about the accuracy of tongue maps). However, sweet is most intense in the front of the tongue and is detected by the facial nerve (cranial nerve VII). The facial nerve receives impulses from the chemoreceptors in the anterior 2/3 of the tongue.

WHICH OF THE FOLLOWING IS ASSOCIATED WITH PARALYSIS OF CRANIAL NERVE VII?

A BELL PALSY

B CORNEAL DAMAGE

C UNILATERAL INABILITY OF THE FRONTAL BELLY OF THE OCCIPITOFRONTALIS TO CONTRACT

D HERPES SIMPLEX VIRUS I

E ALL OF THE ABOVE

Paralysis (palsy) of cranial nerve VII causes significant loss of quality of life.

The vestibulocochlear nerve (cranial nerve VIII) is created by the vestibular branch (which monitors equilibrium and balance) and by the cochlear branch (which is responsible for hearing). It is a purely sensory nerve.

The vestibular branch of cranial nerve VIII relays information to the brain so we can maintain balance and equilibrium.

Example of activities monitored by the vestibular branch of cranial nerve VIII

The cochlear branch of cranial nerve VIII relays information to the auditory portions of the brain so we can hear.

Example of activity detected by cochlear branch of cranial nerve VIII

Master Long knows about cranial nerve VIII and can damage hearing by rupturing ear drums and traumatizing the cochlea while simultaneously disrupting balance and equilibrium.

The glossopharyngeal nerve (cranial nerve IX) has motor functions for swallowing and the parotid salivary gland and sensory functions for taste from chemoreceptors on the posterior 1/3 of the tongue.

Swallowing muscles

As stated earlier, there is debate about the accuracy of tongue maps. However, the glossopharyngeal nerve (cranial nerve IX) receives input from chemoreceptors on the posterior 1/3 of the tongue, including bitter.

The vagus nerve (cranial nerve X) is the only cranial nerve to leave the regions of the head and neck. It is a parasympathetic nerve that reduces the activity of many visceral organs, (Surprisingly, parasympathetic nerves inhibit all body systems, except for the digestive system where they have a stimulatory effect!)

It is no wonder that the vagus nerve is called the wanderer!

The motor component of the vagus nerve innervates most throat and larynx muscles. The sensory component receives input from the external auditory canal and eardrum, throat, larynx, heart, lungs, esophagus, and most abdominal organs.

The accessory nerve (cranial nerve XI) arises from both the spinal cord and the brain. It innervates the trapezius and sternocleidomastoid muscles to move the head, neck, and shoulders. It also innervates throat muscles to aid in swallowing.

Damage to left branch of Accessory nerve. This person is at rest and normal tension from right sternocleidomastoid is pivoting neck to left side (“wry neck”).

The hypoglossal nerve (cranial nerve XII) innervates muscles of the tongue for swallowing and speech. It is NOT involved in taste!

Hypoglossal nerve (cranial nerve XII) palsy on left side. Effect is ipsilateral.

Patient undergoing evaluation of his cranial nerve functions. We will do this in a later lab.