The cranial nervesThe 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:• 3rd, 4th, 6th, 11th and 12th.

Mixed:• 5th, 7th, 9th and 10th.

The cranial nervesThe cranial nerves

The cranial nerves Overview

Cr I Olfactory Cr II Optic Cr III Oculomotor Cr IV Trochlear Cr V Trigeminal Cr VI Abducent

Cr VII Facial Cr VIII Vestibulocochlear Cr XI Glossopharyngeal Cr X Vagus Cr XI Accessory Cr XII Hypoglossal

The first two are merely an outdrawn part of the CNS rather than nerves.

The cranial nervesThe cranial nerves

Olfactory:Olfactory: (Sensory) (Sensory) Cr ICr I

Optic: Optic: (sensory) (sensory) Cr IICr II

Fibers originate in the upper part of the nose.

They are unique in being the central processes not peripheral ones

Olfactory:Olfactory: (Sensory) (Sensory) Cr ICr I

•Clinically:Clinically: Bilateral anosmia & CSF leakBilateral anosmia & CSF leak are common signs of head are common signs of head injuries with anterior cranial injuries with anterior cranial fossa fracture. fossa fracture.

Leaves the orbital cavity through the optic canal They join each other to form the chiasma.

OpticOptic:: (sensory) (sensory) Cr IICr II

•ClinicallyClinically::• Section through the optic nerve Section through the optic nerve causes epsilateral blindness.causes epsilateral blindness.• Lesions behind the optic chiasma Lesions behind the optic chiasma (pituitary gland tumors) lead to (pituitary gland tumors) lead to contro-lateral blindness. contro-lateral blindness.

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 nerveOculomotor nerve:: (motor) (motor) Cr IIICr III

Supply all the orbital muscles, except the superior oblique, lateral rectus and levator palpebrae superioris

Supply parasympathic fibers to the constrictors of the pupil.

Oculomotor nerveOculomotor nerve:: (motor) (motor) Cr IIICr III

•Clinically:Clinically:• Inability to look up, down or medially.Inability to look up, down or medially.• Dilatation of the pupil. Dilatation of the pupil. • Ptosis (drooping of the eyelid paralysis Ptosis (drooping of the eyelid paralysis of LPS)of LPS)

Enter through the superior orbital fissure supply the superior oblique muscle

Trochlear nerveTrochlear nerve:: (motor) (motor) Cr IVCr IV

•ClinicallyClinically::•Unable to look downward and Unable to look downward and inward.inward.•Difficulty in walking downstairsDifficulty in walking downstairs

Motor nucleus (branchial) in the upper pons, for the muscles of the first branchial arch.

Sensory nucleus (somatic) divided into three

Mesencephalic Main Spinal

Trigeminal NerveTrigeminal Nerve:: (mixed) (mixed) Cr VCr V

Mesencephalic: extend through the midbrain First order neurons mediate proprioceptive impulses

Main sensory: upper pons lateral to the motor second order neurons mediate touch

Spinal: extend from lower pons, medulla to

spinal cord second order neurons mediate pain & temperature

Trigeminal NerveTrigeminal Nerve:: (mixed) (mixed) Cr VCr V

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.

Trigeminal NerveTrigeminal Nerve:: (mixed) (mixed) Cr VCr V

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

Trigeminal NerveTrigeminal Nerve:: (mixed) (mixed) Cr VCr 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 NerveTrigeminal Nerve:: (mixed) (mixed) Cr VCr V

Nerve to medial pterygoid muscle

Anterior branches: nerves to lateral pterygoid,

masseter and two deep temporal

the long buccal nerve “S”. Posterior branches:

Auriculotemporal inferior alveolar (nerve to

mylohoid “M”) the lingual nerves

Trigeminal NerveTrigeminal Nerve:: (mixed) (mixed) Cr VCr V

Trigeminal NerveTrigeminal Nerve:: (mixed) (mixed) Cr VCr V

ClinicallyClinically• Fracture midface, zygoma or mandible might lead Fracture midface, zygoma or mandible might lead to anaesthesia to light touch and other modalities.to anaesthesia to light touch and other modalities.

• Lesions of the entire nerve leads to Lesions of the entire nerve leads to anaesthesia and paralysis and atrophy anaesthesia and paralysis and atrophy of the muscles of mastication.of the muscles of mastication.

• Trigeminal neuralgiaTrigeminal neuralgia• Herpes zosterHerpes zoster

Somatic, leave the brain through the superior orbital fissure

Supply the lateral rectus muscle.

AbducentAbducent : : (motor) (motor) Cr VICr VI

ClinicallyClinically::

• Strabismus and diplopia Strabismus and diplopia on lateral gazeon lateral gaze

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)

FacialFacial:: (mixed) (mixed) Cr VIICr 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

FacialFacial:: (mixed) (mixed) Cr VIICr VII

ClinicallyClinically::• Bell’s PalsyBell’s Palsy• Loud sound, Loud sound, • paralysis of stapidus muscleparalysis of stapidus muscle

A special sensory nerve, consist of two kinds of fibers, the vestibular and the cochlear

Mediate sound reception and balance.

VestibulocochlearVestibulocochlear:: (sensory) (sensory) CrCr VIIIVIII

•ClinicallyClinically::• DeafnessDeafness• vertigovertigo

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. Chemoreceptor & pressure:

• Carotid sinus concerned with regulation of respiration and circulation

Glossopharyngeal Nerve:Glossopharyngeal Nerve: (mixed)(mixed) Cr IXCr 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

Glossopharyngeal Nerve:Glossopharyngeal Nerve: (mixed)(mixed) Cr IXCr IX

• Clinically:Clinically:• Neuralgia.Neuralgia.• Loss of gagging reflexLoss of gagging reflex

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:Vagus nerve: mixedmixed Cr XCr 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 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

Vagus nerve:Vagus nerve: mixedmixed Cr XCr X

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.

Accessory nerve:Accessory nerve: (Motor) (Motor) Cr XICr XI

Accessory nerve:Accessory nerve: (Motor) (Motor) Cr XICr XI

• ClinicallyClinically::

• Paresis of the laryngeal Paresis of the laryngeal and pharyngeal muscles and pharyngeal muscles leading to dysphonia and leading to dysphonia and dysphagia. dysphagia.

•Paresis of the trapezius Paresis of the trapezius and sternocleidomastoid and sternocleidomastoid muscle following neck muscle following neck dissection for tumour dissection for tumour surgery.surgery.

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

Hypoglossal nerve:: (Motor) (Motor) Cr XIICr XII

• ClinicallyClinically::• Unilateral lingual paresis Unilateral lingual paresis • hemiatrophy of the tongue hemiatrophy of the tongue Dysarthia.Dysarthia.