cranial nerve examination presented by: joseph s. ferezy, d.c

Cranial Nerve Examination

Presented By:

Joseph S. Ferezy, D.C.

Cranial Nerves

12 Pair Control All Motor and Sensory Functions

Involving the Head, Face, and Neck, Including the Special Senses.

Usually Impairs the Patient's Ability to Engage in Normal Conversation Note Facial and Eye Movements Listen to the Patient's Articulation.

Nerve Fibers Mediating Volitional Movement of Cranial Nerve-innervated Musculature Arise Bilaterally From the Precentral Gyrus of

the Cerebral Motor Cortex Descend Along the Corticobulbar Tract (or

Pathway) of the Brain. "Cortico" Refers to the Cortex and "Bulbar" to

the Brainstem. Due to Bilateral Innervation Both the Right and

Left Hemispheres Have Control Over the Right and Left Sides of the Body.

Neurons of the Corticobulbar Tract

Termed Upper Motor or Supranuclear Neurons As the Entire Nerve Cell Resides in the Central

Nervous System Terminate in Different Cranial Nerve Motor

Nuclei in the Brainstem. Synapse With the Lower (or Alpha) Motor

Neurons of the Peripheral Cranial Nerves, Which Go on to Innervate Specific Muscles.

Chiropractic Concepts

Links Between Vestibular Cranial Nerve Nuclei, Cervically Innervated Muscle and Joint Receptors, As Well As Trigeminal (Cranial Nerve V) Nuclei Exist.

These Interconnections Are Thought to Be Responsible for the Clinical Relationships Between Headache and Dizziness and the Neck.

Cervicogenic Pain May Be the Greatest Cause of Headache

Cervicogenic Vertigo May Be the Greatest Cause of Dizziness.

Bilateral Innervation

Lesions of Only One Cerebral Hemisphere Will Not Usually Permanently Paralyze Normally Bilateral Symmetrical Movements.

Exception Is Cranial Nerve VII

Cranial Nerve I

Anatomy and Function Not a Peripheral Nerve but a Central Nervous

System Tract Terminating in the Olfactory Bulb. Special Second-order Ganglion Nerve Cells Pierce

the Cribriform Plate of the Ethmoid Bone and Terminate in the Mucous Membranes That Line the Nasal Cavity.

To Perceive a Smell, Certain Molecules Must Dissolve Into the Mucus Overlying the Cribriform Plate and Supply Chemical Stimulation of the Nerve Endings There.

Disorders

Anosmia (Complete Loss of Smell) Not Indicative of a Cortical Lesion. Perversion, Hallucination, or Diminution of Smell

Would Be More Likely in Cortical Lesions. More Commonly Associated With Viral Infections,

Allergic Rhinitis, Aging, or Head Trauma With Skull Fracture and Fracture of the Cribriform Plate.

CSF Rhinorrhea and Backwash Meningitis Are Possible and Should Be Investigated.

Disorders

Without Fracture, Neck and Head Injuries Can Cause the Cribriform Plate to Shear off Neurons Descending From the Olfactory Bulb.

In All of the Above Conditions but Aging, the Sense of Smell May Eventually Return, but It Often Does Not.

Lesions of the Uncinate Gyrus of the Anterior Temporal Lobe May Cause Hallucinations of Smell Associated With Strong Feelings of Deja Vu, Termed Uncinate Fits or Seizures. May Cause Any Disorder of Smell.

Disorders

Hyposmia (a Decrease of Smell) Hyperosmia (an Increase of Smell) Parosmia (a Perversion of Smell) Cacosmia (Abnormally Disagreeable

Smell)

Less Frequent Causes of Disorders of Smell

Frontal Lobe Tumors May Compress the Olfactory Tract Tumors Involving the Structures Surrounding

the Olfactory Tract, Such As Meningiomas.

Examination Not Routinely Tested. May Be Tested When Complaints Include Changes in

Smell And/or Taste. One Nostril Must Be Occluded Patient Closes His or Her Eyes. Ask the Patient What He or She Smells Prior to Placing

Any Substance Near the Patient. Use a Substance Producing a Nonirritating Smell

Peppermint Coffee Lemon

Examination

Place Under the Patient's Nose

A Different Smell Should Be Used for the Other Nostril.

Cranial Nerves II, III , IV, And VI (The Visual System)

Normal Ocular Anatomy

Bulbar and Palpebral Conjunctivae

Medial and Lateral Canthi

Limbus

Cornea Ciliary Body of the Iris Lens Retina Choroid Sclera

Anatomy and Function

Optic Nerve Is Not a True Cranial Nerve but Rather a Central Nervous System Tract

Retina Is a Specialized Sensory Ending Central Vision

Retinal Area Upon Which the Visual Image Is Focused The Fovea Centralis of the Macula Lutea. Color Vision Greatest Concentration of Cone Receptors. Damage Results in a Corresponding Decrease in

Central Visual Acuity.


Retinal Rod Receptors Are Responsible for Black-and-white Peripheral Vision. Function in Very Low Light Conditions Pathology Affecting Their Numbers May Be

Responsible for Night Blindness or Tunnel (Gun Barrel) Vision.


Fibers From the Lateral Portion of the Retina Pass Through the Optic Nerve Without Synapsing or Decussating at the Optic Chiasm.

Fibers From the Medial Retina Cross at the Optic Chiasm Without Synapsing.

All Fibers Then Travel Posteriorly, With the Lateral Fibers Ipsilateral and the Medial Fibers Contralateral, As the Optic Tract and Synapse in Either the Pretectal Nucleus or the Lateral Geniculate Body


From the Lateral Geniculate Body, Fibers Travel Through the Optic Radiation to the Calcarine Fissure of the Occipital Lobe.

This Area Is Referred to As the Striate or Primary Visual Cortex.

A Strict Laminated Organization of Fibers Is Maintained From the Retina to the Primary Visual Occipital Cortex.

Even the Firing Pattern of Neurons in the Striate Cortex After Visual Stimulation Maintains the Physical Characteristics of the Shape of the Stimulus.

Oculomotor (III ), Abducens (IV), and Trochlear (IV)

Associated With Extra-ocular Muscular Control.

Corticobulbar (Supra-nuclear) Fibers Descend to Midbrain and Pontine Nuclei, Which in Turn Activate the Lower Motor Neurons Innervating the Extraocular Muscles.

Extra-ocular Muscles

Superior Oblique (Trochlear) Lateral Rectus (Abducens) Medial Rectus (Oculomotor) Superior Rectus (Oculomotor) Inferior Rectus (Oculomotor) Inferior Oblique (Oculomotor)

Extra-ocular Muscles

Cranial Nerve IV Causes the Eye to Move Down When It Is Internally Deviated

Cranial Nerve VI Causes It to Move Laterally Cranial Nerve III Causes It to Move in All Other

Directions. Associated With

Levator Palpebrae (Oculomotor) Superior Tarsal (Sympathetic Innervation Via the

Superior Cervical Sympathetic Ganglia).

Eye Light Reflexes

Cranial Nerve III Is Also Associated With Pupil Constriction.

Impulses Generated by the Stimulation of Photosensitive Retinal Sensors Travel Back Through the Optic Nerve.

After Passing the Optic Chiasm, Impulses Travel Along the Optic Tract.

Impulses Pass to the Pretectal Nucleus in the Midbrain, for Equal Distribution to the Ipsilateral and Contralateral Edinger-westphal Nuclei.

Eye Light Reflexes

Impulses Stimulate Parasympathetic Fibers That Travel Along Cranial Nerve III to the Episcleral Ganglion

Then to the Pupilloconstrictor Muscle.

Eye Light Reflexes

Light Perceived in Any Quadrant of the Visual Field of One Eye Will Cause Constriction of the Pupil of the Eye Receiving the Stimulus (Direct Reflex)

Also Constriction, to an Equal Extent, of the Pupil of the Other Eye (Consensual Reflex).

Cranial Nerve II Is the Sensory Are of This Reflex.

Parasympathetic Fibers Traveling Along Cranial Nerve III Comprise the Motor Arc.

Eye Light Reflexes

Sympathetic Nervous System Is Responsible for the Regulation of Pupil Dilation.

Sympathetic Motor Fibers Exiting From the Upper Thoracic Region of the Spinal Cord Ascend the Paravertebral Sympathetic Ganglion Chain to the Superior Cervical Ganglion.

Eye Light Reflexes

Ascend Along the Internal Carotid Arteries and Go on to Innervate the Pupillodilator Muscle.

Some Go to the Superior Tarsal Muscle. Other Fibers Ascend Along the External Carotid

Arteries to Innervate the Sweat Glands and Control Vasoconstriction for the Face.

Horner's Syndrome

Visual Field Deficits

Objects Situated in the Nasal (Medial) Half of the Visual Field Are Projected Onto the Temporal Retinal Surface

Objects in the Temporal (Lateral) Half Are Projected Onto the Nasal Retinal Surface.

Objects in the Upper Visual Field Are Projected Onto the Surface of the Lower Retina

Objects in the Lower Visual Field Are Projected Onto the Surface of the Upper Retina

Deviations of Eye Alignment

Termed Heterotropias ("Hetero," Different; "Tropia,“ Place)

Named for the Direction of the Ocular Deviation. Modifiers

Left Right Alternating Intermittent


Exotropia: Outward/lateral Esotropia: Inward/medial Hypertropia: up Hypotropia: Down


Disorders Involving Cranial Nerves III , IV, and VI and Their

Nuclei Ophthalmoplegia

Internuclear Connections Internuclear Ophthalmoplegia

Supra Nuclear Connections (UMN's) Gaze Palsy

Ophthalmoplegia

At the Nuclear or Peripheral Level Cranial Nerve VI

The Patient Is Unable to Laterally Deviate the Eye on the Side Ipsilateral to the Lesion.

Cranial Nerve IV Disease Causes Difficulty for the Patient When Looking Down and in.

Disease of Cranial Nerve III Is Usually More Obvious Due to the Accompanying Parasympathetic Manifestations (Eyelid Ptosis and Corectasia).

Internuclear Ophthalmoplegia

Medial Longitudinal Fasciculus (MLF) Whose Primary Function Is to Coordinate Eye

Movements (Also Known As Yoked Movement) by Interconnecting the Nuclei of Cranial Nerves III , IV, and VI.

Disease of These Interconnecting Pathways May Produce a Characteristic Internuclear Ophthalmoplegia.

Internuclear Ophthalmoplegia MLF Lesion Often Multiple Sclerosis Causes Paralysis of Medial Gaze, So That Whichever

Direction the Patient Is Instructed to Look Toward, One Eye Can Not Deviate Nasally.

Both Eyes Will Converge When Testing Accommodation. (Convergence Requires Only Function of Cranial Nerve III Bilaterally).

Lateral Gaze Requires the Use of Two Separate Cranial Nerves, III and VI, to Move One Eye Inward and One Eye Outward.

Supranuclear Pathways

Two Separate Pathways! Frontal Lobe

Mostly Saccadic (Rapid or Darting) Eye Movements Occipital Lobe

Smooth or Following Eye Movements.

Nystagmus (Involuntary Eye Oscillations) Is the Result of Uncoordinated Attempts at Controlling Eye Movement Fast Component Representing Saccadic Movement Slow Portion Representing Following Movement.

Disorders of Pupil Function

Disease of Cranial Nerve II Will Diminish Pupilloconstriction With Bilateral Symmetry Due to Decreased Sensory Perception (Associated With Visual Loss.)

Exposure of the Uninvolved Side Should Cause Brisk Bilateral Pupilloconstriction.


Involvement of the Motor Arc of the Reflex (Cranial Nerve III) Results in a Decreased Pupilloconstriction in the Ipsilateral Eye.

Loss of Diencephalon or Midbrain Function Results in Unopposed Sympathetic (Pupillodilator) Dominance; Light As a Stimulus Causes No Pupilloconstriction, and the Pupil Is Fixed and Dilated.


Adie's Pupil (Tonic Pupil) Reacts to Light Very Slowly Remains Constricted Longer Then Dilates Slowly. It Is Considered a Benign Condition and Occurs Most Often in

Young Women. Argyll Robertson Pupil

Reacts Only to Accommodation Has Neither a Direct nor an Indirect Reaction to Light. Once Considered Pathognomonic of Tabes Dorsalis

(Neurosyphilis) May Occur As a Diabetic Complication.

Horner's Syndrome

Often Due to Lesions of the Neck Proximal to the Carotid Artery Bifurcation.

Compress Ascending Sympathetic Fibers.

Horner's Syndrome

Mild or Moderate Ptosis Due to Paralysis of the Superior Tarsal Muscle and Muscle

of Muller. Pupilloconstriction (Cormiosis)

Due to Unopposed Cranial Nerve III Pupilloconstriction Facial Anhydrosis (I.E., Lack of Sweating)

Due to Denervation of the Sweat Glands in the Ipsilateral Side of the Head

Ipsilateral Facial Vasodilatation Causing a Red or Flushed Look and a Palpable Increase in

Skin Temperature.

Partial Horner’s Syndrome

Lesions Along the Sympathetic Pathway Distal to the Bifurcation of the Common Carotid Arteries Cause Only Pupilloconstriction and Ptosis

If Occurring Along the Internal Carotid Path Cause Vasodilatation and Anhydrosis, If

Occurring Along the External Carotid Pathway.

Enophthalmos

An Inward Sinking of the Eyeball in the Eye Socket, Is Theoretically a Part of Sympathetic Paralysis Due to Disruption of Sympathetic Contractile Impulses to the Small Muscle of Muller. It Has Been Suggested That It Is the Enophthalmos Which Causes the Characteristic “Pseudoptosis”

Examination

You Must First Ask Yourself Three Questions in Order to Fully Evaluate the Visual System: (1) What Do the Eyes Look Like From the

Outside? (2) How Do the Eyes Function (What Can the

Patient See)? (3) What Do the Eyes Look Like on the

Inside?

Examination

All Procedures Requiring Introduction of a Light Source (Ophthalmoscope, Penlight, Etc.) Are Performed After Testing for Central and Peripheral Vision.

Observation-what Do the Eyes Look Like From the Outside?

Eyelid Ptosis Hypothalamic Brainstem Spinal Cord Peripheral Cranial Nerve III Peripheral Sympathetics Neuromyal Pathways Muscular Local Causes

Pupil Asymmetries


Ocular Alignment Head Tilting Due to Ocular Deviation or Paralysis Can

Cause Significant Cervical Spine Somatic Dysfunction. The Patient Is Instructed to Keep the Eyes

Focused Straight Ahead in the Distance. Note

The Upper Eyelid Covers the Superior Aspect of the Iris, Without Covering Any Part of the Pupil.

Lower Eyelid Should Form a Tangent With the Limbus or Outer Edge of the Iris (Limbus-to-lid Distance).


The Same Amount of Scleral Tissue Should Be Visible Both Medial and Lateral to the Iris (Limbus to Canthi), and None Should Be Visible Above or Below It..


With Complete Abduction or Adduction of the Eye No Scleral White Should Be Seen on the Side of the Iris in the Direction of the Patient's Gaze.

Conditions Which Lead to Erroneous Diagnosis of Eye Deviation Canthus Dystopia Epicanthal Folds Hypertelorism Hypotelorism Enophthalmos Micro- and

Macrophthalmos Micro- and

Macrocornea.


Follow up an Abnormal Observation With Corneal Reflection Test (Discussed Below).

Ciliospinal Reflex

Pinch the Skin on the Patient's Neck Observe for Brisk Bilateral Pupillodilation.

Assessment of the Visual Fields--what Can The Eyes See?

Central Vision Snellen Eye Chart.

First Number Represents the 20-foot Distance Betweenthe Patient and the Chart

Second Number Represents the Distance in Feet at Which a ''Normal" Individual Can Correctly Read a Given Lineof the Chart.

A 25% Reproduction of the Chart Used at aDistance of 5 Feet, or Newsprint Held at Arm'sLength, May Suffice for Practical Clinical Purposes.


Questions Regarding Central Visual Function May Warrant Patient Referral to an Optometrist or Ophthalmologist.

Occlude Vision in One Eye. Corrected Vision Is Tested. Each Eye Is Separately Tested. Legal Blindness Is a Legal Issue Medical Blindness Is Failure to Perceive Light

Stimulus.


Peripheral Vision. Confrontation.

Occlude One of Your Eyes The Patient Is to Fix Gaze on Your Nose and Not

to Deviate From This Point. The Eyes of the Patient Must Always Be in Plain

View. The Urge to Deviate the Eyes As One Waits to

See an Object in the Periphery Is Very Great, butPeeking Voids the Test.

Confrontation

The Patient Is Instructed to Point to Any Object You Bring Into His or Her Visual Field.

Preferably, the Object Will Have a RedTip, Such As a Pencil With an Eraser

Your Fingertips May Be Used. The Object Is Brought From Some Point Outside of Vision Into the Center of One of the

FourQuadrants of Vision.

Test at Least Four Quadrants for Each Eye.

Confrontation

Ask the Patient to Say "Moving" Immediately If He or She Sees That the Object Is Moving

Further Refinement May Be Made by Placing Two or Three Fingers in the Visual Field Being Tested and Asking the Patient to Tell How Many Fingers He or She Sees.

Note the Patient's Accuracy Be Sure That You Cast No Shadows That

Could Alert the Patient As to Your Movements.

Visual Extinction (Inattention)

Certain Cerebral Lesions Suppress Vision but Do Not Alter Classic Visual Pathways

A Patient Suffering From InattentionWill Not Notice a Visual Stimulus on One Body Side When It Is Accompanied by a Simultaneous Stimulus on the Opposite Side.

Parieto-occipital Lobe Lesions May Yield Contralateral Inattention.

Assessment of Extraocular Movement

Ask the Patient to Keep His or Her Eyes on Your Finger Without Moving the Head.

Your Finger Should Be Several Feet in Front of the Patient's Eyes (If Too Close Nystagmus May Result)

Move Through the Six Cardinal Fields of Gaze. Hold up the Eyelids of the Patient When Testing

Downward Gaze Cause Enough Eye Movement As to Approximate

Eye Limbus to Canthus, Both Medially and Laterally.

Assessment of Extraocular Movement Bring Your Finger Slowly to Within 6 Inches of the

Patient's Nose and Note Accommodation. It Consists of Three Components

Convergence Pupilloconstriction, Lens Thickening

Convergence Is Accomplished by the Medial Recti Muscles and Is Dependent on Cranial Nerve III Function.

Pupilloconstriction Is Accomplished Via Parasympathetic Fibers Traveling Within Cranial Nerve III .


Two Objectives Look for Full, Concomitant Movement of Both Eyes Movement Should Not Include Nystagmus. It Is Essential That the Patient Report

Any Diplopia. If Ocular Deviation Is Detected, It Is Essential to Note

Whether or Not Ocular Movement Is the Same in Both Eyes (Concomitant).

If It Is, Then the Likelihood of Extraocular Muscle Paralysis Is Small.

If Not Concomitant, Then Extraocular MuscleParalysis Should Be Suspected.


Concomitant Eye Movement Along With OcularDeviation May Be Caused by a Disturbance of Image Formation Due, for Instance, to a Cloudy Cornea, Refractory Error, Cataract, or Macular Lesion.

Non-concomitant Eye Movement Results inDiplopia Due to the Brain's Inability to Resolve the Dual Images.

Nystagmus

An Involuntary To-and-fro Eye Oscillation. Physiological or “End-point” Nystagmus Is

Common. Pathological Nystagmus Usually Begins Well

Before the Patient Is at the Visual End-point. May Also Be Congenital and Benign. The Typical Clinical Picture Accompanying

Nystagmus of Recent Onset Includes Nausea, Vertigo, Vomiting, and Ataxia.

Nystagmus

Jerk The Side Toward Which the Quick Component of the

Nystagmus (Saccadic) Travels Is the Side That Bears the Name.

Pendular Nystagmus Usually Occurs in Both Eyes but May

Occur in Only One, Especially in Intranuclear Ophthalmoplegias.

Horizontal Vertical Plane Rotary

What Do the Eyes Look Like on the Inside?

Ophthalmoscopy and Related Procedures

Corneal Light Reflection

To Verify Any Suspicion of Ocular Malalignment Observe the Relative Position of the Two Points of

Reflection of the Ophthalmoscope's Light, One in Each Eye, on the Patient's Corneas.

With the Patient's Eyes Focused Straight Ahead, the Reflection From a Light Source Shined Directly Into Both Eyes Should Be Located Slightly Medial to the Corneal Center.

A Modification of This Test May Supplementor Even Replace the Classic Examination for Extraocular Movement, in Selected Cases.

Corneal Light Reflection

If Full, Pain-free, Non-symptom-provoking Cervical Ranges of Motion Are Obtainable, and Nystagmus Does Not Become Evident.

Place a Weakly Lit Ophthalmoscope in Front of the Patient and Instruct Them to Look Directly Into the Ophthalmoscope Light.

Gently Direct Active Movement of the Patient' S Head, Sufficient to Test the Cardinal Fields of Gaze.

Do Not Forget to Test Accommodation Without Using the Ophthalmoscope Light.

Eye Light Reflexes

Light Introduced Into the Pupil of One Eye Will Cause Reflex Constriction of Both Pupils, Equally.

The Patient Is Instructed to Look Forward Into the Distance Directly.

Carefully Observe the Size of One Pupil Introduce, at a Distance of 2 to 6 Inches, a

Beam of Light From the Ophthalmoscope. Note the Degree and Speed of

Pupilloconstriction.

Eye Light Reflexes

Remove the Light Source Without Taking Your Eye off of the Pupil, and Observe for Right-sided Pupillodilation.

Observing the Other Pupil, Shine the Light Into the Same Pupil Again.

Observe for Left Pupilloconstriction, of Equal Degree and Speed to the Previous Opposite Side Pupilloconstriction.

Remove the Light Source, and Observe for Pupillodilation. You Can and Should Repeat the Test Three to Four Times to Recheck Any Questionable or Presumed Abnormalities.

Eye Light Reflexes

Repeat the Above Procedure for the Other Eye.

If a Cruder Source of Light, Such As a Penlight, Must Be Used, It Is a Good Idea to Block the Possible Spillover of Light Into Both Pupils Simultaneously During Testing.

The Swinging Flashlight Test

Is a Simple and Sensitive Method to Test Equal Pupil Constriction.

Apparent Pupillodilation With Light Introduction Is Known As the Marcus-Gunn Phenomenon.

The Light Source Is Introduced Into One Pupil and Then the Other Pupil in Continuous Succession.

The Patient's Pupil Does Not Dilate When Light Is Introduced but Constricts Slightly Less Than When the Light Was Introduced to the Other Pupil.

Marcus-Gunn Phenomenon.

Indicates a Retinal or Cranial Nerve II Lesion With the Sensory Arc Decreasing the Amount of Pupillary (Motor) Response.

Optic Neuritis, Often an Early Sign of Multiple Sclerosis, Is the Most Frequent Cause.

Red Reflex

The So-called Red Reflex Is Not a Reflex! This Term Refers to a Yellow-to-reddish Light

Reflection Seen Through the Ophthalmoscope When It Is Held at Distances Greater Than About 6 Inches From a Patient's Pupil.

Any Partial or Complete Blocking of This Reflection Indicates Disease of the Translucent Structures of the Eye, Such As the Cornea, Lens, or Vitreous, or of the Retinal Pigment .

cranial nerve examination presented by: joseph s. ferezy, d.c

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