Upload
nilesh
View
218
Download
0
Embed Size (px)
Citation preview
8/14/2019 Cranial Nerves and Its Examination
1/136
Cranial nerves and its
examination
8/14/2019 Cranial Nerves and Its Examination
2/136
Components of nervous system
8/14/2019 Cranial Nerves and Its Examination
3/136
Names of cranial nerves
8/14/2019 Cranial Nerves and Its Examination
4/136
Classification Sensory cranial nerves: contain only afferent (sensory) fibers
I Olfactory nerve
II Optic nerve
VIII Vestibulocochlear nerve
Motor cranial nerves: contain only efferent (motor) fibers III Oculomotor nerve
IV Trochlear nerve VI Abducent nerve
XI Accessory nerve
XII Hypoglossal nerve
Mixed nerves: contain both sensory and motor fibers--- V Trigeminal nerve,
VII Facial nerve,
IX Glossopharyngeal nerve
X Vagus nerve
8/14/2019 Cranial Nerves and Its Examination
5/136
Human Anatomy, Frolich, Head/Neck IV: Cranial Nerves
Special Sense NervesI,II,VIII
Somatic Motor Nerves
EyeIII,IV,VITongueXII
Face and jaws
VII, VRest of body nerves
IX,X,XI
8/14/2019 Cranial Nerves and Its Examination
6/136
Nomenclature
Somatic - Relating to the skeleton or skeletal
(voluntary) muscle.
Visceral Relating to (involuntary) muscle and its
(autonomic) innervation. An organ of the digestive,
cardiac, respiratory, urogenital, and endocrine
systems.
8/14/2019 Cranial Nerves and Its Examination
7/136
Special Relating to special sense
organs (smell, vision,equilibrium and
hearing)
Afferent incoming,sensory
Efferent Outgoing, motor
8/14/2019 Cranial Nerves and Its Examination
8/136
Functional components
General somatic afferent fibers (GSA): transmitexteroceptive and proprioceptive impulses fromhead and face to somatic sensory nuclei (V)
General somatic efferent fibers (GSE): innervateskeletal muscles of eye and tongue (III, IV, VI, XII)
8/14/2019 Cranial Nerves and Its Examination
9/136
General visceral afferent fibers (GVA):transmit interoceptive impulses from theviscera to the visceral sensory nuclei (VII,IX, X)
General visceral efferent fibers (GVE):transmit motor impulses from the generalvisceral motor nuclei and relayed in
parasympathetic ganglions. Thepostganglionic fibers supply cardiacmuscles smooth muscles and glands(III,VII,IX, X)
8/14/2019 Cranial Nerves and Its Examination
10/136
Specialcomponents
Special visceral afferent fibers (SVA): transmit sensoryimpulses from special sense organs of smell and taste to thebrain (VII, IX, X,I)
Special somatic afferent fibers (SSA): transmit sensory
impulses from special sense organs of vision, equilibriumand hearing to the brain (VIII)
8/14/2019 Cranial Nerves and Its Examination
11/136
Special visceral efferent fibers (SVE):
transmit motor impulses from the brain to
skeletal muscles derived from brachial
arches of embryo. These include themuscles of mastication, facial expression
and swallowing (V, VII, IX, X, XI)
8/14/2019 Cranial Nerves and Its Examination
12/136
General concept
Motor nuclei send fibers directly to
muscles
Nuclei for cardiac, visceral and glands
send fibers to autonomic ganglion for
relay.
Sensory nuclei cell bodies of second
neuron, first neurons are outside CNS in
the gaglion.
8/14/2019 Cranial Nerves and Its Examination
13/136
The central process of the cells in the
nuclei go to three sensory destination
1. Motor nuclei for reflex
2. Cerebellum
3. Opposite thalamus for relay in sensory
cortex.
8/14/2019 Cranial Nerves and Its Examination
14/136
I. Olfactory nerve
-is a special visceral
afferent (SVA) nerve
that mediates the
sense of smell(olfaction).
the only cranial nerve
that projects directly
to the forebrain
8/14/2019 Cranial Nerves and Its Examination
15/136
Enter the bulb to synapse on mitral
cells.
The central processe pass in the
olfactory tract to anterior perforatedsubstance and uncus
The olfactory system consists of the
olfactory epithelium, bulbs and tractsalong with olfactory areas of the
brain collectively known as the
rhinencephalon
8/14/2019 Cranial Nerves and Its Examination
16/136
Clinical correlation- CN I damage
-results in anosmia, loss of olfactory
sensation
8/14/2019 Cranial Nerves and Its Examination
17/136
II.Optic nerve
special somatic afferent
nerve
Arises from the retina of the
eye Optic nerves pass through
the optic canals and
converge at the optic chiasm
Lateral geniculate body
relay and sorting station.
8/14/2019 Cranial Nerves and Its Examination
18/136
8/14/2019 Cranial Nerves and Its Examination
19/136
Clinical correlations-CN II
-When it is transected, ipsilateral blindness and
loss of direct pupillary light reflex result;
regeneration of the optic nerve does not occur. -When it is subjected to increased intracranial
pressure (e.g., tumor), papilledema, a "choked"
optic disk results.
When it is constricted, optic atrophy (i.e., axonal
degeneration) results.
8/14/2019 Cranial Nerves and Its Examination
20/136
III. Occulomotor
contains general somatic efferent and
general visceral efferent fibers.
Is a pure motor nerve that moves the eye,
constricts the pupil, Accommodates and
converges.
8/14/2019 Cranial Nerves and Its Examination
21/136
III.Occulomotor
NUCLIE
Nucleus of oculomotor
Motor to superior, inferior and medial recti; inferiorobliquus; levator palpebrae superioris
Accessory nucleus of oculomotor(Edinger- Westphal)
Parasympathetic to sphincter pupillea and ciliary muscle
Leaves the skull through - Superior orbital fissure
8/14/2019 Cranial Nerves and Its Examination
22/136
8/14/2019 Cranial Nerves and Its Examination
23/136
Ciinical correlations-CN III
1. Oculomotor paralysis is seen frequently with
transtentorial herniation (subdural, epidural
hematoma).
-results in diplopia (double vision) when thepatient looks in the direction of the paretic
muscle.
Results on ptosis, loss of accomodation and
dilatation of pupil.
8/14/2019 Cranial Nerves and Its Examination
24/136
IV.Trochlear
Is a pure GSE nerve that innervates the
superior oblique muscle,which
depresses, intorts, and abducts the eye.
Nuclei - trochlear nucleus of the
midbrain.
Passes through the lateral wall of the
cavernous sinus,
Leaves the skull - superior orbital fissure.
8/14/2019 Cranial Nerves and Its Examination
25/136
Clinical correlations
CN IV paralysis
results in the following
conditions:
1. Extorsion of the
eye and weakness ofdownward gaze
2. Vertical diplopia,
which increases when
looking down
8/14/2019 Cranial Nerves and Its Examination
26/136
V. Trigeminal nerve
Components of fibers SVE fibers: originate from motor nucleus of
trigeminal nerve, and supply masticatorymuscles
GSA fibers: transmit facial sensation tosensory nuclei of trigeminal nerve, the GSAfibers have their cell bodies in trigeminal
ganglion, which lies on the apex of petrouspart of temporal bone
8/14/2019 Cranial Nerves and Its Examination
27/136
Nuclei
One motor and three sensory
Motor
Masticatory muscle, mylohyoid, tensor palati
Sensory
1. Mesencephalic Propioception for muscle of
mastication, face, tongue, orbit
2. Main sensory Touch from trigeminal area3. Spinal nucleus Pain and temprature from
trigeminal area
8/14/2019 Cranial Nerves and Its Examination
28/136
Branches
Ophthalmic nerve (V1,sensory) leave the skull
through the superior orbitalfissure, to enter orbital cavity
Branches
Frontal nerve:
Supratrochlear nerve
Supraorbital nerve
Lacrimal nerve
Nasociliary nerve
8/14/2019 Cranial Nerves and Its Examination
29/136
8/14/2019 Cranial Nerves and Its Examination
30/136
Maxillary nerve(V2, sensory)
Leave skull through
foramen rotundum
Branches
Infraorbital nerve Zygomatic nerve
Superior alveolar
nerve
Pterygopalatine
nerve
8/14/2019 Cranial Nerves and Its Examination
31/136
Distribution:
Sensation from cerebral
dura mater Maxillary teeth
Mucosa of nose andmouth
Skin between eye andmouth
8/14/2019 Cranial Nerves and Its Examination
32/136
Mandibular nerve(V3,mixed)
Leave the skull through the
foramen ovale to enter the
infratemporal fossa
Branches
Main trunk nervous spinosusand nerve to medial pterygoid
Anterior trunk buccal nerve,
nerve to massticatory muscles.
Posterior trunk auricuotemporal, lingual, inferior
alveolar.
8/14/2019 Cranial Nerves and Its Examination
33/136
Distribution:
Sensation from cerebral dura mater
Teeth and gum of lower jaw
Mucosa of floor of mouth
Anterior 2/3 of tongue
Skin of auricular and temporal
regions and below the mouth
Motor to masticatory muscles,
mylohyoid, and anterior belly of
digastric
Parotid gland sensory throughauriculotemporal nerve
8/14/2019 Cranial Nerves and Its Examination
34/136
8/14/2019 Cranial Nerves and Its Examination
35/136
Clinical correlations-lesions of
CN V
1. Loss of general sensation from the face
and mucous membranes of the oral and
nasal cavities
2. Loss of the corneal reflex
4. Deviation of the jaw to the weak side,
due to the unopposed action of the
opposite lateral pterygoid muscle
8/14/2019 Cranial Nerves and Its Examination
36/136
VI Abd t
8/14/2019 Cranial Nerves and Its Examination
37/136
VI Abducent Fibers leave the inferior pons and enter the orbit
via the superior orbital fissure
Arises from the abducent nucleus of the caudalpons
Primarily a motor nerve innervating the lateralrectus muscle (abducts the eye; thus the name
abducent)
8/14/2019 Cranial Nerves and Its Examination
38/136
Clinical correlations-CN VI
paralysis
Is the most common isolated muscle palsy.
Results in the following conditions:
1. Convergent strabismus (esotropia), with the
inability to abduct the eye due to the unopposed
action of the medial rectus muscle
2. Horizontal diplopia, with maximum separationof the double when looking toward the paretic
lateral rectus muscle
8/14/2019 Cranial Nerves and Its Examination
39/136
Facial nerve (V)Components of fibers
SVE fibers originate from nucleus of facial nerve, and supply
facial muscles
GVE fibers derived from superior salivatory nucleus and relayed
in pterygopalatine ganglion and submandibular ganglion. The
postganglionic fibers supply lacrimal, submandibular and
sublingual glands
SVA fiber from taste buds of anterior two-thirds of tongue which
cell bodies are in the geniculate ganglion of the facial nerve and
end by synapsing with cells of nucleus of solitary tract
GSAfibers from skin of external ear
8/14/2019 Cranial Nerves and Its Examination
40/136
Course: leaves skull through
internal acoustic meatus,
facial canal and
stylomastoid foramen, it
then enters parotid gland
where it divides into five
branches which supply facial
muscles
8/14/2019 Cranial Nerves and Its Examination
41/136
Branches within the facial canal Chorda tympani :joins lingual branch of mandibular
nerve
To taste buds on anterior two-thirds of tongue
Relayed in submandibular ganglion, the
postganglionic fibers supply submandibular and
sublingual glands
Greater petrosal nerve: GVE fibers pass to
pterygopalatine ganglion and there relayed through thezygomatic and lacrimal nerves to lacrimal gland
Stapedial nerve : to stapedius
8/14/2019 Cranial Nerves and Its Examination
42/136
Branches outside of facial canal
Temporal
Zygomatic
Buccal
Marginal mandibular
Cervical
8/14/2019 Cranial Nerves and Its Examination
43/136
Clinical correlations-lesions of
8/14/2019 Cranial Nerves and Its Examination
44/136
Clinical correlations-lesions ofCN VII
1. Flaccid paralysis of the muscles of facialexpression (upper and lowl face)
2. Loss of the corneal (blink) reflex (efferent
limb), which may leads corneal ulceration(keratitis paralytica)
3. Loss of taste (ageusia) from the anterior
two-thirds of the tongue4. Hyperacusis (increased acuity to sounds),due to stapedius paralysis
8/14/2019 Cranial Nerves and Its Examination
45/136
5. Bell palsy - vis caused by trauma to the nervewithin the facial canal. It is a lower motor neuron(LMN) lesion with paralysis of all muscles offacial expression.
6. Central facial palsy- (supranuclear palsy)(UMN).
-results in contralateral facial weakness belowthe orbit.
-frontalis and orbicularis occuli escape due tobilateral representation in cerebral cortex
8/14/2019 Cranial Nerves and Its Examination
46/136
7. Crocodile tears syndrome (lacrimationduring eating) is caused by a facialnerve lesion proximal to the geniculate
ganglion. Regenerating 'preganglionic salivatory
fibers are misdirected to the
pterygopalatine ganglion, which projectsto the lacrimal gland.
C i l N VIII
8/14/2019 Cranial Nerves and Its Examination
47/136
Cranial Nerve VIII:
Vestibulocochlear Two divisions cochlear (hearing) and
vestibular (balance)
Functions are solely sensory equilibrium and
hearing Fibers arise from the hearing and equilibrium
apparatus of the inner ear, pass through the
internal acoustic meatus, and enter the
brainstem at the pons-medulla border
8/14/2019 Cranial Nerves and Its Examination
48/136
Cranial Nerve VIII: Vestibulocochlear
Figure VIII from Table 13.2
8/14/2019 Cranial Nerves and Its Examination
49/136
Clinical correlation
lesions of the vestibular nerve
-result in disequilibrium, vertigo, and
nystagmus.
lesions of the cochlear nerve
-result in hearing loss (sensorineural
deafness)
-cause tinnitus (irritative lesions).
8/14/2019 Cranial Nerves and Its Examination
50/136
Glossopharyngeal nerve (IX)
Components of fibers SVEfibers: originate from nucleus ambiguus, and
supply stylopharygeus
GVE fibers: arise from inferior salivatory nucleus
and ralyed in otic ganglion, the postganglionic fiberssupply parotid gland (secretomotor)
SVA fibers: arise from the cells of inferior ganglion,the central processes of these cells terminate innucleus of solitary tract, the peripheral processessupply the taste buds on posterior third of tongue
8/14/2019 Cranial Nerves and Its Examination
51/136
GVA fibers: visceral sensation from mucosa
of posterior third of tongue, pharynx,
auditory tube and tympanic cavity, carotid
sinus, and end by synapsing with cells ofnucleus of solitary tract
GSA fibers: sensation from skin of posterior
surface of auricle
8/14/2019 Cranial Nerves and Its Examination
52/136
Course: leaves the skull via jugular foramen
Branches
Lingual branches : to taste buds and mucosa ofposterior third of tongue
Pharyngeal branches : take part in forming the
pharyngeal plexus
Tympanic nerve : GVE fibers via tympanic and lesser
petrosal nerves to otic ganglion, with postganglionic
fibers via auriculotemporal ( 3) to parotid gland
Carotid sinus branch : innervations to carotid sinus
Others: tonsillar and stylophayngeal branches
8/14/2019 Cranial Nerves and Its Examination
53/136
Cli i l l ti l i f
8/14/2019 Cranial Nerves and Its Examination
54/136
Clinical correlations-lesions of
CN IX
1. Loss of the gag (pharyngeal) reflex
2. Loss of the carotid sinus reflex
3. Loss of taste from the posterior third ofthe tongue
4. Glossopharyngeal neuralgia
8/14/2019 Cranial Nerves and Its Examination
55/136
8/14/2019 Cranial Nerves and Its Examination
56/136
Vagus nerve (X)components of fibers
GVE fibers: originate from dorsal nucleus of vagusnerve, synapse in parasympathetic ganglion, shortpostganglionic fibers innervate cardiac muscles,smooth muscles and glands of viscera
SVE fibers: originate from ambiguus, to muscles ofpharynx and larynx
GVA fibers: carry impulse from viscera in neck,thoracic and abdominal cavity to nucleus of solitarytract
GSA fiber: sensation from auricle, external acousticmeatus and cerebral dura mater
8/14/2019 Cranial Nerves and Its Examination
57/136
Branches in neck
Superior laryngeal nerve:
Internal branch, which pierces thyrohyoid
membrane to innervates mucous membrane of
larynx above fissure of glottis
External branch, which innervates cricothyroid
Cervical cardiac branches : descending to
terminate in cardiac plexus
Others: auricular, pharyngeal and meningeal
branches
8/14/2019 Cranial Nerves and Its Examination
58/136
Branches in thorax
Recurrent laryngeal nerves
Right one hooks around right
subclavian artery, left one hooks
aortic arch
Both ascend in tracheo-esophageal
groove
Innervations: laryngeal mucosa
below fissure of glottis , all laryngeal
muscles except cricothyroid
Bronchial and esophageal branches
8/14/2019 Cranial Nerves and Its Examination
59/136
Branches in
abdomen
Anterior and posteriorgastric branches
supply pyloric part
Hepatic branches:
supply liver and
gallbladder
Celiac branches:
sympathetic fibers to
liver, pancreas, spleen,
kidneys, intestine
8/14/2019 Cranial Nerves and Its Examination
60/136
Clinical correlations lesions of
8/14/2019 Cranial Nerves and Its Examination
61/136
Clinical correlations-lesions of
CN X
1. Ipsilateral paralysis of the soft palate,pharynx, and larynx leading to dysphonia
(hoarseness), dyspnea, dysarthria, anddysphagia
2. Loss of the gag (palatal) reflex
3. Anesthesia of the pharynx and larynx,leading to unilateral loss of the coughreflex
8/14/2019 Cranial Nerves and Its Examination
62/136
XI Accessory
Mediates head and shoulder movement andinnervates laryngeal muscles.
1. Cranial division
-arises from the nucleus ambiguus of the medulla.
--exits the medulla and joins the vagal nerve --exits the skull via the jugular foramen with CN IX
and CN X.
-innervates the intrinsic muscles of the larynx via
the inferior (recurrent) laryngeal nerve, with theexception of the cricothyroid muscle.
8/14/2019 Cranial Nerves and Its Examination
63/136
2. Spinal division
-arises from the ventral horn of cervical segments
CI-C6.
-Spinal roots exit the spinal cord laterally betweenthe ventral and dorsal spinal roots, ascend through
the foramen magnum, and exit skull via the jugular
foramen.
-innervates the sternocleidomastoid (with C2) andtrapezius rn cles (with C3 and C4
8/14/2019 Cranial Nerves and Its Examination
64/136
Clinical correlations lesions of
8/14/2019 Cranial Nerves and Its Examination
65/136
Clinical correlations - lesions of
CN XI
1. Paralysis of the sternocleidomastoid muscle
-results in difficulty in turning the head to the side
opposite the lesion.
2. Paralysis of the trapezius muscle-results in a shoulder droop.
-results in the inability to shrug the ipsilateral
shoulder.3. Paralysis of the larynx occurs if the cranial root
is involved
8/14/2019 Cranial Nerves and Its Examination
66/136
Hypoglossal Nerve (CN XII)
A. General characteristics-CN XII
-mediates tongue movement.
-arises from the hypoglossal nucleus of
the medulla.
-exits the skull via the hypoglossal canal. -innervates intrinsic and extrinsic muscles
of the tongue except palatoglossus .
8/14/2019 Cranial Nerves and Its Examination
67/136
B Clinical correlations CN XII
8/14/2019 Cranial Nerves and Its Examination
68/136
B. Clinical correlations-CN XII
-When it is transected, hemiparalysis of
the tongue results.
-When it is protruded, the tongue points
toward the weak side due to theunopposed action of the opposite
genioglossus muscle
Terminal nerve or Cranial nerve
8/14/2019 Cranial Nerves and Its Examination
69/136
Terminal nerve orCranial nerve
zero
It was first found in humans in1913, although its presence in humansremains controversial.
However, a study has indicated that theterminal nerve is a common finding in theadult human brain.
It projects from the nasal cavity, enters the
brain as a microscopic plexus ofunmyelinated peripheral nerve fascicles.
8/14/2019 Cranial Nerves and Its Examination
70/136
The nerve is often overlooked in autopsies because itis unusually thin for a cranial nerve, and is often tornout upon exposing the brain. Careful dissection isnecessary to visualize the nerve
It is very close to and often confused for a branch ofthe olfactory nerve, This fact suggests that the nerve iseither vestigial or may be related to the sensingof pheromones.
The nerve zero projects to the medial and lateral septal
nuclei, and the preoptic areas all of which are involvedin regulating sexual behavior in mammals.
8/14/2019 Cranial Nerves and Its Examination
71/136
Neurologic examinationCRANIAL NERVES
Cranial Nerves Exam
8/14/2019 Cranial Nerves and Its Examination
72/136
Olfaction depends on the integrity of the olfactory neurons in the
roof of the nasal cavity and their connections through the
olfactory bulb, tract to the olfactory cortex
To test olfaction:
1. An odorant, such as concentrated vanilla, perfume or coffee,
is presented to each nostril in turn.
2. The patient is asked to sniff (with eyes closed) and identifyeach smell.
Olfaction is frequently not tested because of unreliable patient
responses and lack of objective signs.
CRANIAL NERVE I (OLFACTORY NERVE)
Cranial Nerve I
8/14/2019 Cranial Nerves and Its Examination
73/136
Cranial Nerve I
Cranial Nerves Exam
8/14/2019 Cranial Nerves and Its Examination
74/136
Evaluation gives important information about the nerves,
optic chiasm, tracts, thalamus, optic radiations, and visual
cortex.CN 2 is also the afferent limb of the pupillary light reflex.The optic nerve is tested in the office by visual acuity
measurement, color vision testing, pupil evaluation, visual field
testing, and optic nerve evaluation via ophthalmoscopy
CRANIAL NERVE 2 (OPTIC NERVE)
II O ti
http://medicine.tamu.edu/neuro/05.gifhttp://medicine.tamu.edu/neuro/05.gif8/14/2019 Cranial Nerves and Its Examination
75/136
II - Optic
Examine the Optic Fundi
http://medicine.tamu.edu/neuro/05.gifhttp://medicine.tamu.edu/neuro/05.gifhttp://medicine.tamu.edu/neuro/05.gif8/14/2019 Cranial Nerves and Its Examination
76/136
Test Visual Acuity
1. Allow the patient to use their glasses if available. You are
interested in the patient's best corrected vision.
2. Position the patient 20 feet in front of the Snellen eye
chart3. Have the patient cover one eye at a time with a card.
4. Ask the patient to read progressively smaller letters until
they can go no further.
5. Record the smallest line the patient read successfully
Repeat with the other eye.
8/14/2019 Cranial Nerves and Its Examination
77/136
There are hand held cards that look like Snellen Charts but are positioned
14 i h f th ti t Th d i l f i T ti
8/14/2019 Cranial Nerves and Its Examination
78/136
14 inches from the patient. These are used simply for convenience. Testing
and interpretation are as described for the Snellen.
Hand held visual acuity card
8/14/2019 Cranial Nerves and Its Examination
79/136
Screen Visual Fields
1. Stand two feet in front of the patient and have them lookinto your eyes.
2. Hold your hands about one foot away from the patient's
ears, and wiggle a finger on one hand.
3. Ask the patient to indicate which side they see the finger
move.
4. Repeat two or three times to test both temporal fields.
5. If an abnormality is suspected, test the four quadrants of
each eye while asking the patient to cover the opposite
eye with a card.
8/14/2019 Cranial Nerves and Its Examination
80/136
8/14/2019 Cranial Nerves and Its Examination
81/136
Test Pupillary Reactions toAccommodation
Hold your finger about 10cm from the patient's nose.
Ask them to alternate looking into the distance and at
your finger.
Observe the pupillary response in each eye.
8/14/2019 Cranial Nerves and Its Examination
82/136
The pneumonic:
S O 4 L R 6 All The Rest 3may help remind you which CN does what
CRANIAL NERVE 3 (OCULOMOTOR NERVE)
CRANIAL NERVE 4 (TROCHLEAR NERVE)
CRANIAL NERVE 6 (ABDUCENS NERVE)
8/14/2019 Cranial Nerves and Its Examination
83/136
Observe for Ptosis
Test Extraocular Movements1.Stand or sit 3 to 6 feet in front of the patient.
2.Ask the patient to follow your finger with their eyes
without moving their head.
3.Check gaze in the six cardinal directions using a
cross or "H" pattern.
4.Pause during upward and lateral gaze to check for
nystagmus.
5.Check convergence by moving your finger toward
the bridge of the patient's nose.Test Pupillary Reactions to Light
8/14/2019 Cranial Nerves and Its Examination
84/136
8/14/2019 Cranial Nerves and Its Examination
85/136
Testing CN III, IV, and VI:To test the extraocular muscles, have thepatient follow a target through the sixprincipal positions of gaze ("H" pattern).
8/14/2019 Cranial Nerves and Its Examination
86/136
Right CN3 Lesion: Note patient's right eye is deviated
laterally and there is ptosis of the lid.
8/14/2019 Cranial Nerves and Its Examination
87/136
Right CN3 Lesion: The right pupil (upper left picture) is
more dilated than the left pupil.
8/14/2019 Cranial Nerves and Its Examination
88/136
8/14/2019 Cranial Nerves and Its Examination
89/136
CRANIAL NERVE 5 (TRIGEMINAL)
8/14/2019 Cranial Nerves and Its Examination
90/136
Assessment of CN 5 Sensory Function:
Use a sharp implement Ask the patient to close their eyes so that they
receive no visual cues. Touch the sharp tip of the stick to the right and
left side of the forehead, assessing theOphthalmic branch. Touch the tip to the right and left side of the
cheek area, assessing the Maxillary branch.
Touch the tip to the right and left side of thejaw area, assessing the Mandibular branch. The patient should be able to clearly identify
when the sharp end touches their face.
CRANIAL NERVE 5 (TRIGEMINAL)
CRANIAL NERVE 5 (TRIGEMINAL)
8/14/2019 Cranial Nerves and Its Examination
91/136
To assess this component:
1. Pull out a wisp of cotton.
2. While the patient is looking
straight ahead, gently brushthe wisp against the lateralaspect of the sclera (outerwhite area of the eye ball).
3. This should cause the patient toblink.
Blinking also requires that CN 7function normally, as itcontrols eye lid closure.
CRANIAL NERVE 5 (TRIGEMINAL)
The Ophthalmic branch of CN 5 also receives sensory input
from the surface of the eye.
CRANIAL NERVE 5 (TRIGEMINAL)
8/14/2019 Cranial Nerves and Its Examination
92/136
Assessment of CN 5 Motor Function:
Place your hand on both Temporalis muscles, located onthe lateral aspects of the forehead.
Ask the patient to tightly close their jaw, causing themuscles beneath your fingers to become taught.
Then place your hands on both Masseter muscles.
Ask the patient to tightly close their jaw, which should againcause the muscles beneath your fingers to become taught.Then ask them to move their jaw from side to side, functionof lateral and medial pterygoid
CRANIAL NERVE 5 (TRIGEMINAL)
The motor limb of CN 5 innervates the Temporalis and
Masseter muscles, both important for closing the jaw.
CRANIAL NERVE 5 (TRIGEMINAL)
8/14/2019 Cranial Nerves and Its Examination
93/136
CRANIAL NERVE 5 (TRIGEMINAL)
CRANIAL NERVE 7 (FACIAL)
8/14/2019 Cranial Nerves and Its Examination
94/136
This nerve innervates muscles of facial expression.
Assessment is performed as follows: First look at the patients face. It should appearsymmetric.
There should be the same amount ofwrinkles apparent on either side of theforehead
The nasolabial folds should be equal The corners of the mouth should be at the
same height
If there is any question as to whether anapparent asymmetry if new or old, ask thepatient for a picture for comparison.
CRANIAL NERVE 7 (FACIAL)
8/14/2019 Cranial Nerves and Its Examination
95/136
CRANIAL NERVE 7 (FACIAL)
8/14/2019 Cranial Nerves and Its Examination
96/136
Interpretation:
CN 7 has a precise pattern of innervation, whichhas important clinical implications.
The right and left upper motor neurons (UMNs)
each innervate both the right and left lowermotor neurons (LMNs) that allow the forehead tomove up and down.
However, the LMNs that control the muscles of the
lower face are only innervated by the UMN fromthe opposite side of the face.
CRANIAL NERVE 7 (FACIAL)
Central Facial Paralysis (Central Seven)
8/14/2019 Cranial Nerves and Its Examination
97/136
caused by a lesion of the corticonuclear (corticobulbar) tract above thelevel of the facial nucleus (upper motor neuron lesion)
causes paralysis/paresis of the muscles of the contralateral lower face upper part of facial nucleus contains motor neurons that innervatemuscles of upper face it is innervated by ipsilateral and contralateralcorticonuclear fibers unilateral lesion of corticonuclear tract does notaffect muscles of upper face on either side
lower part of facial nucleus contains motor neurons that innervatemuscles of lower face it is innervated only by contralateralcorticonuclear fibers unilateral lesion of corticonuclear tract (abovethe level of facial nucleus) affects muscles of lower face on opposite sideof lesion
8/14/2019 Cranial Nerves and Its Examination
98/136
8/14/2019 Cranial Nerves and Its Examination
99/136
Textbook Fig. 25-14
8/14/2019 Cranial Nerves and Its Examination
100/136
8/14/2019 Cranial Nerves and Its Examination
101/136
Right central CN7 dysfunction:
Note preserved ability to wrinkle forehead.
Left corner of mouth, however, is slightly lower than right.
Left nasolabial fold is slightly less pronounced compared with right.
8/14/2019 Cranial Nerves and Its Examination
102/136
CRANIAL NERVE 7 (FACIAL)
8/14/2019 Cranial Nerves and Its Examination
103/136
Interpretation:
LMN dysfunction: This occurs most commonly in the settingof Bells Palsy, an idiopathic, acute CN 7 peripheral
nerve palsy. In the setting of R CN 7 peripheral (LMN)
dysfunction, the patient would not be able to wrinkle
their forehead, close their eye or raise the corner oftheir mouth on the right side. Left sided function would
be normal.
( )
8/14/2019 Cranial Nerves and Its Examination
104/136
Left peripheral CN7 dysfunction:
Note loss of forehead wrinkle, ability to close eye, ability to raise corner of
mouth, and decreased nasolabial fold prominence on left.
8/14/2019 Cranial Nerves and Its Examination
105/136
8/14/2019 Cranial Nerves and Its Examination
106/136
Left peripheral CN7 dysfunction:
Note loss of forehead wrinkle, ability to close eye, ability to raise corner of
mouth, and decreased nasolabial fold prominence on left.
8/14/2019 Cranial Nerves and Its Examination
107/136
CRANIAL NERVE 8 (ACOUSTIC)
8/14/2019 Cranial Nerves and Its Examination
108/136
CN 8 carries sound impulses from the cochlea to the brain.
Prior to reaching the cochlea, the sound must firsttraverse the external canal and middle ear.
Assessment is performed as follows: Stand behind the patient and ask them to close their
eyes. Whisper a few words from just behind one ear. The
patient should be able to repeat these back accurately.Then perform the same test for the other ear.
Alternatively, place your fingers approximately 5 cmfrom one ear and rub them together. The patientshould be able to hear the sound generated. Repeatfor the other ear.
CRANIAL NERVE 8 (ACOUSTIC)
8/14/2019 Cranial Nerves and Its Examination
109/136
These tests are rather crude. Precisequantification, generally necessary whenever
there is a subjective decline in acuity
Hearing is broken into 2 phases: conductive andsensorineural.
The conductive phase refers to the passage of
sound from the outside to the level of CN 8. This
includes the transmission of sound through theexternal canal and middle ear.
8/14/2019 Cranial Nerves and Its Examination
110/136
Sensorineural refers to the transmission ofsound via CN 8 to the brain.
Identification of conductive (a much more
common problem in the generalpopulation) defects is determined as
follows:
CRANIAL NERVE 8 (ACOUSTIC)
8/14/2019 Cranial Nerves and Its Examination
111/136
Weber Test
1. Grasp the 512 Hz tuning fork by the stem and strike it against the
bony edge of your palm, generating a continuous tone.
2. Hold the stem against the patients skull, along an imaginary
line that is equidistant from either ear.
3. The bones of the skull will carry the sound equally to both the
right and left CN 8. Both CN 8s, in turn, will transmit theimpulse to the brain.
4. The patient should report whether the sound was heard equally
in both ears or better on one side then the other (referred to as
lateralizing to a side).
CRANIAL NERVE 8 (ACOUSTIC)
8/14/2019 Cranial Nerves and Its Examination
112/136
Weber Test
CRANIAL NERVE 8 (ACOUSTIC) Webber test
8/14/2019 Cranial Nerves and Its Examination
113/136
Interpretation: In the setting of a conductive hearing loss (e.g. wax in the
external canal), the Webber test will lateralize (i.e. sound will beheard better) in the ear that has the subjective decline inhearing. This is because when there is a problem withconduction, competing sounds from the outside cannot reachCN 8via the external canal. Thus, sound generated by thevibrating tuning fork and traveling to CN 8 by means of bonyconduction is better heard as it has no outside competition.
In the setting of a sensorineural hearing loss (e.g. a tumor ofCN 8), the Webber test will lateralize to the ear which does nothave the subjective decline in hearing. This is because CN 8 isthe final pathway through which sound is carried to the brain.Thus, even though the bones of the skull will successfully transmitthe sound to CN 8, it cannot then be carried to the brain due to
the underlying nerve dysfunction.
CRANIAL NERVE 8 (ACOUSTIC)
8/14/2019 Cranial Nerves and Its Examination
114/136
1. Grasp the 512 Hz tuning fork by the stem and strike itagainst the bony edge of your palm, generating acontinuous tone.
2. Place the stem of the tuning fork on the mastoid bone,
The vibrations travel via the bones of the skull to CN 8,allowing the patient to hear the sound.
3. Ask the patient to inform you when they can no longerappreciate the sound. When this occurs, move thetuning fork such that the tines are placed right next to
(but not touching) the opening of the ear. At this point,the patient should be able to again hear the sound. Thisis because air is a better conducting medium thenbone.
Rinne Test:
CRANIAL NERVE 8 (ACOUSTIC)
8/14/2019 Cranial Nerves and Its Examination
115/136
Rinne Test:
CRANIAL NERVE 8 (ACOUSTIC)
8/14/2019 Cranial Nerves and Its Examination
116/136
Rinne Test:
8/14/2019 Cranial Nerves and Its Examination
117/136
CRANIAL NERVE 8 (ACOUSTIC)
8/14/2019 Cranial Nerves and Its Examination
118/136
Summary:
First determine by history and crude acuity testingwhich ear has the hearing problem.
Perform the Webber test. If there is a conductivehearing deficit, the Webber will lateralize to the
affected ear. If there is a sensorineural deficit, theWebber will lateralize to the normal ear.
Perform the Rinne test. If there is a conductive hearingdeficit, BC will be greater then or equal to AC in theaffected ear. If there is a sensorineural hearing deficit,
AC will be greater then BC in the affected ear.
CRANIAL NERVE 9 (GLOSSOPHARYNGEAL)
CRANIAL NERVE 10 (VAGUS)
8/14/2019 Cranial Nerves and Its Examination
119/136
These nerves are responsible for raising the soft palate ofthe mouth and the gag reflex, a protective mechanismwhich prevents food or liquid from traveling into thelungs. As both CNs contribute to these functions, theyare tested together.
Testing Elevation of the soft palate:
Ask the patient to open their mouth and say, ahhhh,causing the soft palate to rise upward.
Look at the uvula.
The Uvula should rise up straight and in the midline.
CRANIAL NERVE 10 (VAGUS)
CRANIAL NERVE 9 (GLOSSOPHARYNGEAL)
CRANIAL NERVE 10 (VAGUS)
8/14/2019 Cranial Nerves and Its Examination
120/136
Normal Oropharynx
CRANIAL NERVE 10 (VAGUS)
CRANIAL NERVE 9 (GLOSSOPHARYNGEAL)
CRANIAL NERVE 10 (VAGUS)
8/14/2019 Cranial Nerves and Its Examination
121/136
Interpretation:
If CN 9 on the left is not functioning, the uvula will be pulled to the right.
C 0 ( GUS)
CRANIAL NERVE 9 (GLOSSOPHARYNGEAL)
CRANIAL NERVE 10 (VAGUS)
8/14/2019 Cranial Nerves and Its Examination
122/136
Left peritonsillar abscess: infection within left tonsil has
pushed uvula towards the right.
CRANIAL NERVE 10 (VAGUS)
CRANIAL NERVE 9 (GLOSSOPHARYNGEAL)
CRANIAL NERVE 10 (VAGUS)
8/14/2019 Cranial Nerves and Its Examination
123/136
Testing the Gag Reflex: Ask the patient to widely open their mouth. If
you are unable to see the posterior pharynx(i.e. the back of their throat), gently push down
with a tongue depressor. In some patients, the tongue depressor alone
will elicit a gag. In most others, additionalstimulation is required. Take a cotton tipped
applicator and gently brush it against theposterior pharynx or uvula. This shouldgenerate a gag in most patients.
CRANIAL NERVE 10 (VAGUS)
CRANIAL NERVE 9 (GLOSSOPHARYNGEAL)
CRANIAL NERVE 10 (VAGUS)
8/14/2019 Cranial Nerves and Its Examination
124/136
CN 9 is also responsible for taste originating on the
posterior 1/3 of the tongue.
CN 10 also provides parasympathetic innervation to the
heart, though this cannot be easily tested on physical
examination.
CRANIAL NERVE 10 (VAGUS)
CRANIAL NERVE 11 (SPINAL ACCESSORY)
8/14/2019 Cranial Nerves and Its Examination
125/136
CN 11 innervates the muscles which permit shrugging of
the shoulders (Trapezius) and turning the headlaterally (Sternocleidomastoid).
Assessment is performed as follows: Place your hands on top of either shoulder and ask the
patient to shrug while you provide resistance.Dysfunction will cause weakness/absence ofmovement on the affected side.
Place your open left hand against the patients rightcheek and ask them to turn into your hand while you
provide resistance. Then repeat on the other side. Theright Sternocleidomastoid muscle causes the head toturn to the left, and vice versa.
CRANIAL NERVE 11 (SPINAL ACCESSORY)
8/14/2019 Cranial Nerves and Its Examination
126/136
CRANIAL NERVE 11 (SPINAL ACCESSORY)
8/14/2019 Cranial Nerves and Its Examination
127/136
CRANIAL NERVE 12 (HYPOGLOSSAL)
8/14/2019 Cranial Nerves and Its Examination
128/136
CN 12 is responsible for tongue movement.Each CN 12 innervates one-half of the tongue.
Assessment is performed as follows:
Ask the patient to stick their tongue straight out of theirmouth.
If there is any suggestion of deviation to one
side/weakness, direct them to push the tip of their
tongue into either cheek while you provide counterpressure from the outside.
CRANIAL NERVE 12 (HYPOGLOSSAL)
8/14/2019 Cranial Nerves and Its Examination
129/136
CRANIAL NERVE 12 (HYPOGLOSSAL)
8/14/2019 Cranial Nerves and Its Examination
130/136
Interpretation: If the right CN 12 is dysfunctional, the tongue will deviate
to the right. This is because the normally functioning lefthalf will dominate as it no longer has opposition from theright. Similarly, the tongue would have limited or absent
ability to resist against pressure applied from outside theleft cheek.
CRANIAL NERVE 12 (HYPOGLOSSAL)
8/14/2019 Cranial Nerves and Its Examination
131/136
Left CN 12 Dysfunction: Stroke has resulted in L CN 12 Palsy.
Tongue therefore deviates to the left.
8/14/2019 Cranial Nerves and Its Examination
132/136
Testing the hypoglossal nerve.Patient is instructed to stick out the tongueand then move it laterally against resistance.
Cranial Nerve Number Innervation(s) PrimaryF i ( )
Test(s)
Summary
8/14/2019 Cranial Nerves and Its Examination
133/136
Function(s)
Olfactory I Sensory Smell Identify odors
Optic II Sensory Vision Visual acuity,fields, color,nerve head
Oculomotor III Motor Upper lid elevation,extraocular eyemovement, pupil
constriction,accommodation
Physiologic "H"and near pointresponse
Trochlear IV Motor Superior obliquemuscle
Physiologic "H"
Trigeminal V Motor Muscles of mastication
Corneal reflex
Trigeminal V Sensory Scalp, conjunctiva,teeth
Clenchjaw/palpate,light touchcomparison
Abducens VI Motor Lateral rectus muscle Abduction,physiologic "H"
8/14/2019 Cranial Nerves and Its Examination
134/136
Facial VII Motor Muscles of facial expression Smile, puff cheeks, wrinklef h d
8/14/2019 Cranial Nerves and Its Examination
135/136
forehead, pryopen closed lids
Facial VII Sensory Taste-anterior two thirds of tongue
Vestibulocochlear VIII Sensory Hearing and balance Rinne test forhearing, Webertest for balance
Glossopharyngeal IX Motor Tongue and pharynx Gag reflex
Glossopharyngeal IX Sensory Taste-posterior one third oftongue
Vagus X Motor Pharynx, tongue, larynx,thoracic and abdominalviscera
Gag reflex
Vagus X Sensory Larynx, trachea, esophagus
Accessory XI Motor Sternomastoid and trapeziusmuscles
Shrug, head turnagainst
resistance
8/14/2019 Cranial Nerves and Its Examination
136/136