Brain
Forebrain
Midbrain
( brainstem)
Hindbrain
CN III, CN IV
Cerebral
hemispheres
Pons
(brainstem)
CN I
CN V
Diencephalon
(epithalamus,
thalamus,
hypothalamus
Medulla oblongata
(brainstem)
CN IX, CN X, XII
CN II
Spinal Cord CN XI
Cerebellum
Cranial nerves can have:
1. Motor (efferent) fibers
• Voluntary (striated) muscle
• Involuntary(smooth) muscle or glands – by
parasympathetic division of ANS: CN III, VII, IX,
and X.
• Preganglionic fibers emerge from brain and
synapse in a parasympathetic ganglion outside
CNS.
• Postganglionic fibers continue to smooth
muscle/glands.
2. Sensory (afferent) fibers
• General sensation – touch, heat, pressure, etc.
• Sensation from viscera (heart, GI tract, etc.)
• Unique sensations – taste, smell, and those for
vision, hearing, balance
Cranial Parasympathetic ganglia
GENERAL ORGANIZATION OF CRANIAL NERVES
Olfactory Nerve : CN I
Exits the nose
→
cribiform plate
in ethmoid
bone →
olfactory bulb
in anterior
cranial fossa
→ olfactory
tracts →
cerebral cortex
∙sense of
smell
Fracture of ethmoid bone/
leisons of olfactory fibers may
result in partial or totat loss of
smell, anosmia [an-oz-me-ah]=
an inability to detect odors) this
may also dull the sense of taste.
Anosmia may also be caused by
the common cold, allergic
rhinitis, frontal lobe tumors,
trauma, aging.
After head trauma, patient
complains of runny nose
(rhinnorhea): test nasal drip with
dextrose or urine test strips --WHY?
Fibers from nasal half of retina relay info from temporal field of that eye.
Fibers from temporal half of the retina relay info from the nasal field of that
eye.
Nasal fibers cross at chiasm.
http:// www.e-advisor.us/ visual_fields.php
ciliary ganglion.
Pupil Involvement with CN3:
Oculomotor palsies often have
pupillary involvement because the
parasympathetic nerves
innervating the iris travel with the
third nerve.
Pupillary involvement is a crucial
diagnostic sign — compressive
lesions tend to involve the pupil,
while vascular lesions actually spare
it!
CN III palsy
• Largest cranial nerve
• Principal somatic sensory nerve to the face
• Emerges from lateral pons by a large sensory and small motor rootsensory root leads to trigeminal
ganglion. Motor root bypasses ganglion to become part of CN V3.
Sensory Root:
Ophthalmic (V1)– exits by sup orbital fissure to give sensation to cornea, skin of forehead, scalp, eyelids,
nose.
Ciliary ganglion associated with V1. Corneal reflex tests V1.
Maxillary (V2)– exits by foramen rotundum to give sensation over maxilla, upper lip and teeth.
Pterygopalatine (parasymatetic ) ganglion is associated with V2 lacrimal glands, glands of nose and
palate.
Mandibular (V3)– exits by foramen ovale to give sensation over mandible and lower lip and teeth, ant 2/3
of tongue.
Otic and submandibular (parasymp) ganglia associated with V3.
Motor Root: exits with V3 via foramen ovale to supply m. of mastication, mylohyoid, ant belly of digastric,
tensor tympani and tensor veli palatini m.
• Injury : by trauma
(dental, cranial),
tumors, aneurysms,
infection (herpes
zoster ophthalmicus)
can all cause
numbness
• Paralysis of m of
mastication with
deviation of
mandible toward
side of lesionMotor branch of V3
Emerges from between pons
and medulla
exits through sup orbital fissure
to enter the eye
Supply motor fibers to lateral
rectus m of eyeball
(abducts eye)
•
•
•
supplies LR6:
unable to look
LATERALLY
(OUTWARDS)
develop double
vision when looking
to the side of the
lesion
medial deviation of
eye
Most
caused by increased
intracranial pressure or vasculopathic etiologies
(Diabetes, Hypertension).
• Greater petrosal n.
• N. to stapedius
• Chordae typmani n.
• Somatic Motor fibers
• Presynaptic Parasympathetic motor fibers
Special Sensory fibers
With a peripheral(LMN) 7th n lesion:
paralysis of ALL facial muscles on IPSILATERAL side:
pt cannot close eye, wrinkle that side of forehead or raise that corner of
mouth = Bell’s Palsy
With central (UMN) 7th n lesions:
paralysis of LOWER facial muscles on CONTRALATERAL side
(forehead wrinkling possible)--- ex common in stroke
Other signs of 7th n lesions: loss of taste to anterior 2/3 of tongue; dry cornea
equilibrium and motion
hearing
Lesions of CN VIII may cause: tinnitus (ringing of
ears), vertigo (dizziness), loss of hearing.
Lesions may involve either vestibular or cochlear or
both divisions of CN VIII.
Emerges from medulla jugular foramen
Motor(efferent) fibers to stylopharyngeus, and presynaptic
parasym fibers to Otic ganglion for parotid gland
innervation.
Sensory fibers to post 1/3 tongue for taste and general
sensation, and sensory to pharynx, carotid sinus and body
Lesions of CN IX:
gag reflex absent on side of lesion or loss of taste on post
1/3 of tongue (i.e., infection/tumors).
Tumors usually involve IX, X, XI –jugular foramen syndrome
• Motor
• Sensory
Longest course and
most extensive
distribution of all cranial
n.
Pharyngeal Plexus of CN X
• Pharyngeal Plexus of Vagus Nerve: network of nerve fibers innervating most
of palate, larynx, and pharynx.
Located on the surface of the middle pharyngeal constrictor muscle.
Composed of fibers from CN IX, X, XI
(all leave jugular foramen together)
• Sensory Innervation:
– Oropharynx and laryngopharynx
• Motor Innervation:
–
–
–
–
all muscles of pharynx(except stylopharyngeus (direct IX))
all muscles of soft palate(except tensor veli palatini(V3))
pharyngeal constrictors
Palatoglossus (extrinsic tongue and palatine m)
Arise as rootlets from the sides of the spinal cord
pass through jugular foramen.
Motor fibers to SCM and trapezius
Arise from the medulla by
rootlets
exits cranium via hypoglossal canal

runs inferiorly and anteriorly to
tongue
Motor fibers supply all extrinsic and
intrinsic muscles of tongue except
palatoglossus
CN X: isolated lesions uncommon; paralysis of
recurrent laryngeal n
(cancer of larynx or thyroid gland; surgery)
Injury of the recurrent laryngeal n: hoarseness,
dysphonia due to paralysis of vocal cords
Deviation of uvula to normal side
CN XI: injury causes drooping of shoulder
CNXII: injury causes paralysis to ipsilateral side of
tongue—tongue deviates toward affected
side
Hypoglossal N Palsey:
Isolated left LMN leison
Anatomy of Cranial Nerves and foramina of skull:
http://www.youtube.com/watch?v=US6oemgNHGQ
Cranial Nerve and foramina quizzes/tutorials:
http://www.gwc.maricopa.edu/class/bio201/cn/cranial
.htm