1. Cranial Nerve Examination
Presented By:
Joseph S. Ferezy, D.C.

2. 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.

3. 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.

6. 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.

10. 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.

11. Bilateral Innervation
Lesions of Only One Cerebral Hemisphere Will Not Usually Permanently Paralyze Normally Bilateral Symmetrical Movements.
Exception Is Cranial Nerve VII

12. 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.

14. 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.

15. 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.

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

17. 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.

18. 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

19. Examination Place Under the Patient's Nose
A Different Smell Should Be Used for the Other Nostril.

20. 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

23. 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.

24. Anatomy and Function
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.

25. Anatomy and Function
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

26. Anatomy and Function
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.

28. 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.

29. Extra-ocular Muscles Superior Oblique (Trochlear)
Lateral Rectus (Abducens)
Medial Rectus (Oculomotor)
Superior Rectus (Oculomotor)
Inferior Rectus (Oculomotor)
Inferior Oblique (Oculomotor)

30. 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).

31. 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.

32. Eye Light Reflexes
Impulses Stimulate Parasympathetic Fibers That Travel Along Cranial Nerve III to the Episcleral Ganglion
Then to the Pupilloconstrictor Muscle.

34. 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.

35. 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.

36. 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

38. 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

40. Deviations of Eye Alignment
Termed Heterotropias ("Hetero," Different; "Tropia,“ Place)
Named for the Direction of the Ocular Deviation.
Modifiers
Left
Right
Alternating
Intermittent

41. Deviations of Eye Alignment
Exotropia: Outward/lateral
Esotropia: Inward/medial
Hypertropia: up
Hypotropia: Down

43. Deviations of Eye Alignment
Disorders Involving
Cranial Nerves III , IV, and VI and Their Nuclei
Ophthalmoplegia
Internuclear Connections
Internuclear Ophthalmoplegia
Supra Nuclear Connections (UMN's)
Gaze Palsy

44. 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).

46. 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.

47. 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.

48. 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.

49. 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.

50. Disorders of Pupil Function
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.

51. Disorders of Pupil Function
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.

52. Horner's Syndrome
Often Due to Lesions of the Neck Proximal to the Carotid Artery Bifurcation.
Compress Ascending Sympathetic Fibers.

53. 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.

54. 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.

55. 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”

56. 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?

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

58. 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

60. Observation-what Do the Eyes Look Like From the Outside?
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).

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

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

64. Observation-what Do the Eyes Look Like From the Outside?
Follow up an Abnormal Observation With Corneal Reflection Test (Discussed Below).

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

66. Assessment of the Visual Fields--what Can The Eyes See?
Central Vision
Snellen Eye Chart.
First Number Represents the 20-foot Distance Between the Patient and the Chart
Second Number Represents the Distance in Feet at Which a ''Normal" Individual Can Correctly Read a Given Line of the Chart.
A 25% Reproduction of the Chart Used at a Distance of 5 Feet, or Newsprint Held at Arm's Length, May Suffice for Practical Clinical Purposes.

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

68. Assessment of the Visual Fields--what Can The Eyes See?
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, but Peeking Voids the Test.

69. Confrontation
The Patient Is Instructed to Point to Any Object You Bring Into His or Her Visual Field.
Preferably, the Object Will Have a Red Tip, 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 Four Quadrants of Vision.
Test at Least Four Quadrants for Each Eye.

70. 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.

71. Visual Extinction (Inattention)
Certain Cerebral Lesions Suppress Vision but Do Not Alter Classic Visual Pathways
A Patient Suffering From Inattention Will 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.

72. 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.

73. 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 .

74. Assessment of Extraocular Movement
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 Muscle Paralysis Should Be Suspected.

75. Assessment of Extraocular Movement
Concomitant Eye Movement Along With Ocular Deviation 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 in Diplopia Due to the Brain's Inability to Resolve the Dual Images.

76. 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.

77. Nystagmus Jerk Pendular
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

81. What Do the Eyes Look Like on the Inside?
Ophthalmoscopy and Related Procedures

82. 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 Supplement or Even Replace the Classic Examination for Extraocular Movement, in Selected Cases.

83. 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.

86. 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.

87. 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.

88. 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.

90. 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.

91. 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.

92. 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 .