Download Lecture 2 - Cranial Nerve Examination Neurologic Examination A

Lecture 2 - Cranial Nerve Examination
Neurologic Examination
 A thorough neurologic exam can locate the focus of a brain lesion
 A comprehensive Cranial Nerve exam maps out much of the brainstem
 Requires simple portable equipment
 Seven Key Elements
 Mental Status
 Cranial Nerves
 Motor
 Sensory
 Coordination
 Deep Tendon Reflexes (DTRs) and Plantar Reflexes
 Gait
Cranial Nerve Exam
 The cranial nerve exam should be carried out in an orderly fashion
 Do it the same way every time, this way you will not miss any steps
The Olfactory Nerve – CN 1
 Not routinely tested
 Test in any patient with a suspected frontal lobe disorder

Ensure Patency of nasal passage

Pt’s eyes closed, cover one nostril, identify familiar odors
 Mint, Coffee, Vanilla, Lavender
 Avoid Noxious Odors (alcohol).
 Defects

Anosmia  Lack of sense of smell
 Physical Obstruction
Lecture 2 - Cranial Nerve Examination
 Genetic Causes
 Neurologic Defect (head trauma)
 Smoking
 Aging
 Use of cocaine
The Optic Nerve – CN II
Retinal signals travel through this nerve via the Optic Chiasm to the Visual Cortex

Test visual acuity using a handheld card or Snellen chart

Test each eye separately

Directly visualize the nerve with an ophthalmoscope

Use your right hand and right eye to evaluate the patient’s right, and your left
hand and left eye to evaluate the patient’s left

Pay attention to the optic discs.


Visual field testing

Have the patient cover one eye, hold your hands within easy visual distance
from the patient’s face, one hand on each side in the peripheral vision and
quickly hold up 1-2 fingers on each hand

Ask the patient to count the total number of fingers held up


A yellowish orange to creamy pink oval or round structure that lies
medially.
The normal monocular visual field extends approximately 100 degrees
laterally, 60 degrees medially, 60 degrees superiorly and 75 degrees
inferiorly. It is divided into nasal and temporal halves and superior and
inferior altitudinal halves. A blind spot is located 15 degrees temporal to
fixation and just below the horizontal meridian.
Optic disc

The point where the optic nerve enters the retina; not sensitive to light

Simply carries blood vessels and nerves from the retina into the appropriate areas of
the brain.
Lecture 2 - Cranial Nerve Examination

There are no receptors here for vision which is why we have a blind spot.

Damage anywhere in the visual pathway from the eye to the visual cortex can cause specific
deficits in the visual fields of one or both eyes.

Importantly, some visual information from each eye crosses to the opposite side at the optic
chiasm.


Lesions in front of the optic chiasm (optic nerve lesion) cause visual deficits in one eye
– 1&2 on schematic.

Lesions at the optic chiasm – involve only fibers that are crossing over to the opposite
side & these fibers originate in the nasal half of each retina causing blindness in the
temporal half of each field (bitemporal hemianopsia) – 3 on schematic.

Lesions behind the optic chiasm (optic tract, thalamus, white matter, and visual cortex)
cause visual field deficits that are similar for both eyes (homonymous hemianopsia) –
4&5 on schematic.
Clinical correlation

When transected, ipsilateral blindness (amaurosis) and loss of direct pupillary light
reflex results


When subjected to increased ICP (tumor), papilledema is the result


Regeneration of the optic nerve does not occur
A “choked” optic disk
When constricted, optic atrophy results (axonal degeneration)
Optic Nerve – CN II and Oculomotor Nerve – CN III
 Pupillary Testing

The optic nerve (II) is responsible for the afferent limb of the pupillary reflex - it senses
the incoming light.

The oculomotor nerve (III) is responsible for the efferent limb of the pupillary reflex - it
drives the muscles that constrict the pupil

Direct reaction (pupillary constriction in the same eye)

Consensual reaction (pupillary constriction in the opposite eye)
 The swinging flashlight tests direct and consensual responses
Lecture 2 - Cranial Nerve Examination

Accommodation --the pupils constrict while fixating on an object being moved from
far away to near the eye (Oculomotor nerve)
 Pupils will constrict as the focal point shortens.
 Ask the patient to focus on your finger and move it towards the patient in the
midline and watch for pupillary constriction
 Abnormal Pupillary Findings

Argyll-Robertson Pupil
 Seen in Syphilis, and rarely diabetes, the neuropathy results in the loss of
constriction to light but accommodation response is preserved

Marcus-Gunn Pupil (Afferent Pupillary Defect)
 Total absence of response to light or accommodation
 Consensual response preserved
 For example, both pupils always dilate and constrict the same, so that they
appear equal in size to each other. They both constrict when the light is in the
good eye, and they both dilate when the light is in the bad eye
Oculomotor Nerve – CN III
CN III projects postganglionic parasympathetic fibers to the sphincter muscle of the iris (miosis =
constriction) and to the ciliary muscle (accommodation)
 Levator Palpebrae Superioris  CN III Palsy  droopy eyelid
Lecture 2 - Cranial Nerve Examination

Raises upper eyelid
 Medial Rectus

Medial gaze
 Primary = adduction
 Superior Rectus

Upward and inward gaze
 Primary = elevation
 Secondary = intorsion
 Tertiary = adduction
 Inferior Rectus

Downward gaze
 Primary = depression
 Secondary = extorsion
 Tertiary = adduction
 Inferior Oblique

Upward and out gaze
 Primary = extorsion
 Secondary = elevation
 Tertiary = abduction
 CN III – Superior Rectus, Inferior Rectus, Inferior Oblique, Medial Rectus
 CN IV – Superior Oblique
 CN VI – Lateral Rectus
Trochlear Nerve – CN IV
 Superior Oblique
Lecture 2 - Cranial Nerve Examination

Downward and inward gaze
 Primary = intorsion
 Secondary = depression
 Tertiary = abduction

Via the Trochlea (Pulley)
To compensate for IV nerve palsy –the pt will tilt their head toward the unaffected side
Abducens Nerve – CN VI
 Lateral Rectus

Lateral Gaze
 Primary = abduction
Extraocular Muscle Testing
 Check extraocular movements by having the patient look in all directions without moving their
head and ask them if they experience any double vision
 Look for deviation, palsies and nystagmus
Clinical Correlation

Below: Oculomotor Palsy (III)
o Ptosis  “Down and Out”, due to unopposed lateral rectus and superior oblique

Above: Trochlear Palsy (IV)
o

Utilizing head tilt  Superior lateral gaze
Right: Abducens Palsy (VI)
o
Esotropia  Loss of lateral gaze
Trigeminal Nerve – CN V

Sensory Function
 Sensation to distributions as listed
Lecture 2 - Cranial Nerve Examination

 Nerves do not cross the midline  test both sides
 Test by stroking three divisions with swab, pin-prick, temperature

Motor Function (V3)
 Muscles of Mastication
 Ask patient to clench teeth and feel masseters thicken
 If there is pathology in CN V-3: upon mouth opening, jaw will deviate toward
the side of lesion

Corneal Reflex

Cornea sensation provided by V1

Light stroke of cornea with swab causes BILATERAL blinking
 Motor response = CN VII


Paralysis of tensor tympani


Loss of reflex is an indication of pathology at CN V-1
Results in hypoacusis, partial deafness to low-pitched sounds
Trigeminal Neuralgia

(CN V-3)
Tic Douloureux
Lecture 2 - Cranial Nerve Examination

Painful neuropathy of one segment of CN V
Facial Nerve – CN VII
 Sensory (Taste)

Test discrimination of salt, sweet, sour on anterior portion of tongue
 rarely tested
 Motor

Raising Brow  test upper division

Squeezing eyelids  test upper division

Puffing Cheeks  test lower division

Smiling  test lower division
 Clinical Correlation
o Supranuclear Lesion
 Involves corticobulbar pathways
 Produces contralateral weakness of the lower face, with normal function of
upper face
 Bilateral innervations of upper face by corticobulbar fibers
 Unilateral innervation of lower face from contralateral cortical centers
 “Forehead Sparing” Stroke
o Infranuclear Lesion
 Total involvement of the ipsilateral facial muscles, with no area being spared
 Results from lesions of the nerve as it exits from the skull or from involvement
of the facial nucleus in the pons
 Bell’s Palsy
Auditory Nerve – CN VIII
 Cochlear Testing

Identify gross hearing deficits

Rinne Test (Conductive)
 Bone vs Air
Lecture 2 - Cranial Nerve Examination
 Hold Fork on mastoid until no longer audible then place in front of ear
 conductive loss if BC>AC

Weber Test (Sensorineural and Conductive)
 Fork in middle of head
 Sound lateralizes towards side with conductive hearing loss
 Sound lateralizes away from side with sensorineural loss

Can perform formal auditory testing for further delineation of pathology
 Vestibular Testing

Part of the extraocular movement testing (nystagmus)

Gait examination (ataxia)

Station evaluation (may fall on Romberg)
 CN VIII lesions would result in hearing loss, tinnitus, vertigo/dizziness, or nystagmus
Glossopharyngeal Nerve - CN IX
 Sensory Function

Taste in Posterior 1/3 of tongue
 Rarely tested

Sensation to posterior pharynx and tonsils.
 Motor Function (With Vagus Nerve CN X)

Innervates the muscles of the pharynx and palate

Necessary for proper initial phase of swallowing
Vagus Nerve – CN X
 For the cranial nerve X exam we focus mainly on its motor function of the pharynx and larynx
(sensory component comes from CN IX)
Testing of CN IX and X
 Motor Function of the pharynx/larynx is shared by both cranial nerves IX and X
Lecture 2 - Cranial Nerve Examination

Open wide and say “ahhh”
 Look for symmetric elevation of the Uvula
 Bilateral loss = no elevation
 Unilateral Loss = Elevation toward the strong side
 See Faucilar Pillars Converge (each side of posterior pharynx moves medially,
like a curtain)
 Gag Reflex (“In by IX and out by X”)
 Laryngeal Testing – Should see elevation of larynx with swallow
 Hoarseness

Vagus nerve (via recurrent laryngeal) innervates vocal cords
 In a CN X lesion the palate will droop and the uvula will deviate away from the side of the
lesion
Accessory Nerve CN – XI
 Innervates Trapezius and Sternocleidomastoid Muscles
 Testing

Trapezius
 Shoulder Shrug

Sternocleidomastoid
 Head Rotation and Resistance to lateral jaw pressure
 Weakness or inability to do these tests would indicate a CN XI lesion
Hypoglossal Nerve – CN XII
 Provides Motor Function to tongue

Look for fasiculations
 With tongue resting in floor of mouth
 If present, indicates hypoglossal LMN lesion

Have patient stick his/her tongue out at you
Lecture 2 - Cranial Nerve Examination
 Deviates toward the same side of the lesion if one is present

Say “lalalalala”