Cranial Nerve Exam (H&P)

Function of CN I

Smell

Function of CN II

Vision

Function of CN III

Pupil Constricition

Lid Elevation

EOM

Function of CN IV

Downward and internal rotation of eye

Function of CN V

Jaw clenching and lateral movement

Facial sensation

Function of CN VI

Lateral movement of eye

Function of CN VII

Facial Movement

Anterior 2/3 tongue for taste

Function of CN VIII

Hearing

Balance

Function of CN IX

Motor to Pharynx

Posterior ear sensation

Posterior 1/3 taste of tongue

Function of CN X

Motor to palate, phayrnx, and larynx

Sensory with pharynx and larnyx

Function of CN XI

Motor to SCM and Trapezius

Function of CN XII

Motor to tongue

What CN originate from the brain

I

II

How do CN receive innervation

Fibers from both hemispheres of the cerebrum will form two nuclei (left and right) in which the CN will originatie

What is the expections of CN bilateral innervation

CN VII only unilateral innervates the lower face (Forehead is bilateral)
CNXII only recieves the contralateral innervation

When can CN abnormalities arise

Specific lesion to the nerve

Lesion to the nucleus

Communing Pathways from Cortex, Diencephalon, Cerebellum, and Brainstem

Multiple Lesions (MS / Meningitis / CVA)

Pathway of CN I

Olfactory Nerve Fibers

Olfactory Bulb

Primary Olfactory Cortex (Temporal)

How to test CN I

Check patency of nostrils

Ask patient to occlude one nostril and close eyes

Use familiar scent; avoid noxious scents

Check bilaterally with two different scents

Anomsia

Cannot recognize smell

Causes of CN I Abnormality

Blocked Nasal Passage

Trauma

Aging

Parkinson’s

Cocaine

COVID

Fractures to anterior cranial fossa

Unilateral frontal lesion pressing on the olfactory bulb/tract

Pathway of CN II

Fibers of Retina

Optic Disc

Optic Nerve

Optic Chiasm

Optic Tract

Lateral Genticulate Body (Thalamus)

Optic Radiation

Visual Cortex (Occpitial)

How to test CNII

Visual acuity with Snellen or Rosenbaum

Visual fields by confrontation

Fundoscopic exam

How far should someone be from a Snellen chart

20 feet from face

How is visual acuity graded

Top number = distance from the chart

Bottom number = distance at which a normal eye could read

What visual acuity is considered legal blindness

20/200

How far should someone be from a Rosenbaum chart

14 in from face

What are some abnormalities for visual acuity

Dense cataracts (lens opacities)

Near sightedness (myopia)

far sightedness (hyperopia)

Retinal causes (retinal detachment, macular degeneration, diabetic retinopathy, etc.)

Retro-orbital abnormality of vision ( optic neuritis)

What are the types of visual fields

Temporal

Nasal

Where in the pathway would a monocular visual field abnormality be created

Before the optic chiasm

Where in the pathway would a bitemporal visual field abnormality be created

Optic Chiasm

Where in the pathway would a homogenous visual field abnormality be created

Behind the optic chiasm

Cause of Monocular Visual Field Defect

Glaucoma

Optic Neuritis

Retinal Emboli

Cause of Bitemporal Visual Field Defect

Pituitary Tumor

Cause of Homogenous Visual Field Defect

CVA, esp. in occipital or parietal

How can we tell the difference between homogenous visual field loss from occipital vs pariteal lobe CVA

Parietal = Loss of the superior field

Occipital = Loss of the inferior field

Causes of Absent Red Reflex

cataracts

detached retina

retinoblastoma

artificial eye

Causes of Papilledema

Increased ICP

Causes of Enlarged Cup

Chronic Open Angle Glaucoma

What CN control the pupillary response

CN II

CN III

How to test pupillary response

Pupil size

Pupillary reaction to light

Near reaction

Swinging flashlight test

Anisocoria

Unequal pupil sizes

Cause of Anisocoria

Can be normal (esp. if reactive)

Miosis

Pinpoint Pupils

Causes of Miosis

Senile Miosis

Medications (Opioids and Cholinergics)

Horner’s Syndrome

Pontine Hemorrhage

Mydriasis

Dilated Pupils

Causes of Mydriasis

can be normal, esp. if reactive

Medications (Anticholinergics and Sympathomimetics)

Head Injury

What reflexes are tested with pupil assessments

Direct Reflex

Consensual Reflex

Direct Pupil Reflex

A constriction of the pupil in response to direct light

Consensual Pupil Reflex

A constriction of the other pupil in response to light on the opposite pupil

Convergence (Eyes)

The coming together of the eyes for an object close to the face

Accommodation (eyes)

The changing of the lens to focus on a close object

Argyll-Robertson Pupils

Small, irregular pupils that do not react (constrict) to light but do react (constrict) to near reaction testing

What is the medical name of Prostitute’s Pupil

Argyll-Robertson

Causes of Argyll-Robertson Pupils

#1 - Tertiary Syphilis

DM

MS

Midbrain Lesion

Adie’s Pupil

A Unilateral dilated pupil

• Very reduced/delayed reaction to light

• Near reaction Present (may be slowed with slow re-dilation)

• Can blurred vision

• Decreased or absent deep tendon reflexes

Causes of Adie’s Pupil

Damage to parasympathetic nervous system

• idiopathic

• viral infection

• trauma

• tumor

Swinging Light Test

Shine the bright light in one eye and then the other at about 1 second intervals

Swing the light repeatedly between the two

Marcus Gunn Pupil / Relative afferent pupillary defect (RAPD)

When light is shone into unaffected eye- both pupils constrict appropriately

When light is shone into affected eye- pupils constrict less (appears to cause paradoxical dilation)

Due to optic nerve dysfunction

Causes of Marcus Gun Pupil / RAPD

Optic Neuritis

MS

Retinal Detachment

Compression of Nerve

Saccadic Eye Movement

Rapid movement when transitioning from one fixed point to another

Pursuit Eye Movement

Slow movements to maintain fixation on a moving object

Vestibular-positional Eye Movement

Compensates for movement of the head to maintain fixation

What controls saccadic eye movement

Frontal Lobe

What controls pursuit eye movement

Occipital

What controls vestibular-positional eye movement

Cerebellar Vestibular Nuceli

What controls convergent eye movement

Midbrain

What areas of brains are important to assess with eye movement

Brainstem

MLF

Why is the brainstem important for eye movement

Integrates eye movements from all areas of the brain so that both eyes move together

Medial Longitudinal Fasciculus (MLF)

A structure of the brainstem that connects CN III, IV, and VI

How is CN III, IV, and VI tested

Eye position and level of eyelid

Extraocular movements

Exophthalmos

A protrusion of the eye

Cause of Exophthalmos

Hyperthyroid

Retro-Orbital Mass

Enopthalmos

A condition of sunken eyes

Causes of Enopthalmos

Horner’s Syndrome

Orbital Bone Fracture

Ptosis

upper eyelid lower than normal (partial versus complete)

Causes of Ptosis

Congenital,

Horner’s syndrome

third nerve palsy

age

myasthenia gravis

Lid Retraction

Eyelid above the level of top of the iris

Cause of Lid Retraction

Hyperthyroid

Horner’s Syndrome

A triad caused by distruped sympathetic innervation of the eye

• Ptosis

• Miosis

• Anhidrosis

Causes of Horner’s Syndrome

Pancoast Tumor

Trauma

CVA

Carotid Dissection

Strabismus

A condition of eye misaligment

Exotropia

A type of strabismus where one or both eyes are facing outward

Esotropia

A type of strabismus where one or both eyes are facing inward

Hpyertropia

A type of strabismus where one or both eyes are facing upward

Hypotropia

A type of strabismus where one or both eyes are facing down

Palsy of CN III causes the eye to face what direction

Down

Outward

What are the EOM

Superior Recti

Inferior Recti

Medial Recti

Lateral Recti

Superior Oblique

Inferior Oblique

What muscle is controlled by CN VI

Lateral Rectus (Abduction)

What muscle is controlled by CN IV

Superior Oblique (Depress, Abduct, Intort)

Medial Rectus

EOM that causes eye adduction

Superior Rectus

EOM that causes eye to look up

Inferior Oblique

EOM that causes exycylotorsion

What are the nuclei of CN III

Main Motor

Edinger-Westphal

Edinger-Westphal Nucleis

The nucleus of the CN III that provides the parasympathetic nerves

Where does the main motor nucleus of the CN III get its fiber

Corticobulbar Fibers of Cerebrum

Where does Edinger-Westphal nucleus travel to

Iris

Ciliary Muscles

Function of Main Motor Nucleus (CN III)

Turn eye down, up, and medially

Levator Palpebrae Superiores Motor (Raise upper eyelid)

Function of Parasympathetic Nucleus (CN III)

Constrict pupil (Direct and Consensual)

Accommodation

Convergence

Signs of CN III Palsy

Inability to move eye up and in

Diplopia

Ptosis

Dilated Pupil (Nonreactive)

Accommodation Paralysis

Signs of CN IV Palsy

Eye Turned Up and Slightly In

Diplopia with looking down