Transcript The cranial nerves

The cranial nerves
The cranial nerves


These are twelve pairs and numbered from before
backward.
All the nerves are distributed in the head and neck
except the tenth which supply structures in the
thorax and abdomen.
Sensory:

•
1st, 2nd and 8Th.
Motor:
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•
3rd, 4th, 6th, 11th and 12th.
Mixed:

•
5th, 7th, 9th and 10th.
The cranial nerves
Overview
 Cr I
 Cr VII Facial
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 Cr VIII Vestibulocochlear
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Olfactory
Cr II Optic
Cr III Oculomotor
Cr IV Trochlear
Cr V Trigeminal
Cr VI Abducent
 Cr XI
Glossopharyngeal
 Cr X Vagus
 Cr XI Accessory
 Cr XII Hypoglossal
The cranial nerves
 The first two are merely an outdrawn
part of the CNS rather than nerves.

Olfactory: (Sensory) Cr I

Optic: (sensory) Cr II
Olfactory: (Sensory)
Cr I
 Fibers originate in the upper
part of the nose.
 They are unique in being the
central processes not
peripheral ones
•Clinically:
Bilateral anosmia & CSF leak
are common signs of head
injuries with anterior cranial
fossa fracture.
Optic: (sensory)
Cr II
 Leaves the orbital cavity
through the optic canal
They join each other to
form the chiasma.
•Clinically:
• Section through the optic nerve
causes epsilateral blindness.
• Lesions behind the optic chiasma
(pituitary gland tumors) lead to
contro-lateral blindness.
Oculomotor nerve: (motor)
Cr III
 Oculo: Eye + Motor: mover
 Somatic nerve to four of the six muscles of that moves the eye and
the muscle that raises the eyelids
 Enter the orbit through superior orbital fissure
Oculomotor nerve: (motor)
Cr III
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Supply all the
orbital muscles,
except the superior
oblique, lateral
rectus and levator
palpebrae
superioris
Supply
parasympathic
fibers to the
constrictors of the
pupil.
•Clinically:
• Inability to look up, down or medially.
• Dilatation of the pupil.
• Ptosis (drooping of the eyelid paralysis
of LPS)
Trochlear nerve: (motor)
Cr IV
 Enter through the superior orbital fissure
 supply the superior oblique muscle
•Clinically:
•Unable to look downward and
inward.
•Difficulty in walking downstairs
Trigeminal Nerve: (mixed)
Cr V
 Motor nucleus (branchial) in
the upper pons, for the
muscles of the first
branchial arch.
 Sensory nucleus (somatic)
divided into three
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Mesencephalic
Main
Spinal
Trigeminal Nerve: (mixed)
 Mesencephalic:
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extend through the midbrain
First order neurons
mediate proprioceptive impulses
 Main sensory:
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upper pons lateral to the motor
second order neurons
mediate touch
 Spinal:
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extend from lower pons, medulla to
spinal cord
second order neurons
mediate pain & temperature
Cr V
Trigeminal Nerve: (mixed)

Ophthalmic division:
• It is the nerve for the frontonasal process
• emerging through the superior orbital fissure
• divide into three branches:
1-Lacrimal nerve.
2-Frontal nerve.
3-Nasociliary nerve.
Cr V
Trigeminal Nerve: (mixed)
 Maxillary division:
 It is the nerve to the
maxillary process, leaves
the skull through foramen
rotundum and have a very
short course.
• Ganglionic branches
• zygomatic nerve
• posterior superior
alveolar nerve
• Infraorbital nerve
Cr V
Trigeminal Nerve: (mixed)
Cr V
 Mandibular division:
 It is the nerve for the first
pharyngeal arch, very short
and emerges through
foramen ovale
 Accompanied by the motor
root of the trigeminal
nerve
 divide into:
• Anterior division
– all motor except one
• Posterior division
– all sensory except one
Trigeminal Nerve: (mixed)
Cr V
 Nerve to medial pterygoid
muscle
 Anterior branches:
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nerves to lateral pterygoid,
masseter and two deep
temporal
the long buccal nerve “S”.
 Posterior branches:
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Auriculotemporal
inferior alveolar (nerve to
mylohoid “M”)

the lingual nerves

Trigeminal Nerve: (mixed)
Clinically
Cr V
• Fracture midface, zygoma or mandible might lead
to anaesthesia to light touch and other modalities.
• Lesions of the entire nerve leads to
anaesthesia and paralysis and atrophy
of the muscles of mastication.
• Trigeminal neuralgia
• Herpes zoster
Abducent : (motor)
Cr VI
 Somatic, leave the brain through the superior orbital
fissure
 Supply the lateral rectus muscle.
Clinically:
• Strabismus and diplopia
on lateral gaze
Facial: (mixed)
Cr VII
 Joined by the nervus intermedius,
sensory root, in the facial canal in
the temporal bone before it
emerges through the stylomastoid
foramen.
 Passes into the parotid gland and
divides into five motor

Branchial motor branches:
• supply the muscles of the facial
expression (from second
pharyngeal arch)
Facial: (mixed)
Cr VII
 Visceral efferent:

Secretomotor to submandibular &
sublingual salivary gland
 Sensory fibers:
 Visceral afferent
• Taste buds anterior two third of
tongue & soft palate

Somatic afferent
• skin of external auditory meatus and
tympanic membrane
Clinically:
• Bell’s Palsy
• Loud sound,
• paralysis of stapidus muscle
Vestibulocochlear: (sensory)
Cr VIII
 A special sensory nerve, consist of two kinds
of fibers, the vestibular and the cochlear
 Mediate sound reception and balance.
•Clinically:
• Deafness
• vertigo
Glossopharyngeal Nerve: (mixed)
Cr IX
 Sensory:

Special:
• taste from the posterior 1/3 of
tongue.

General sensation:
• from the back of the tongue wall of
the pharynx and the middle ear.
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Chemoreceptor & pressure:
• Carotid sinus concerned with
regulation of respiration and
circulation
Glossopharyngeal Nerve: (mixed)
Cr IX
 Motor:

To the stylopharyngeus muscle
of the pharynx.
 Parasympathetic fibres:

to the otic ganglion, the
postganglionic fibres travel with
the auriculo-temporal nerve to
the parotid
• Clinically:
• Neuralgia.
• Loss of gagging reflex
Vagus nerve: mixed
Cr X

Has the most extensive distribution of all the cranial
nerves, supply the heart and the major part of the
respiratory and alimentary tract.
• Has one sensory and two motor nuclei in the medulla.
• Leave the cranial cavity through the jugular foramen.
• passes vertically down the neck within the carotid sheath.
Vagus nerve: mixed
Cr X
 Have 4 types of fibres:
 Motor fibres to the striated muscles of larynx and pharynx.
•
Paralysis of soft palate, dysphagia and aphonia

Visceral-motor fibres carry impulses to thoracic and abdominal viscera

Sensory fibres
• for pain from external auditory meatus
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Visceral fibres:
• Taste buds in the epiglottis
• Stretch receptors in the heart, aorta and common carotid bifurcation
(Blood Pressure and heart rate)
• Stretch receptors in the lung and upper G-T I (rate and depth of
respiration
Accessory nerve:
 A small cranial root which
is distributed to the
muscles of the palate,
pharynx and larynx.
 A large spinal root to the
sternocleidomastoid and
trapezius muscles.
(Motor)
Cr XI
Accessory nerve:
• Clinically:
• Paresis of the laryngeal
and pharyngeal muscles
leading to dysphonia and
dysphagia.
•Paresis of the trapezius
and sternocleidomastoid
muscle following neck
dissection for tumour
surgery.
(Motor)
Cr XI
Hypoglossal nerve: (Motor)
Cr XII
 Leave the posterior cranial
fossa via the hypoglossal canal
in the occipital bone.
 Supply the intrinsic and the
extrinsic muscles of the
tongue with the exception of
the palatoglossus
• Clinically:
• Unilateral lingual paresis
• hemiatrophy of the tongue
Dysarthia.