DR PALLAV RAJ

Surgical Anatomy of Cranial Nerves

CONTENTS

Introduction Functional component Cranial nerves Course Surgical anatomy Conclusion Reference

INTRODUCTION

Nervous System

Central Nervous System

Brain

Spinal Cord

Peripheral Nervous System

12 pairs of Cranial Nerves

31 pairs of Spinal nerves

CRANIAL NERVES

I. Olfactory II. OpticIII. OcculomotorIV. Trochlear V. Trigeminal VI. Abducens

VII. Facial VIII. VestibulocochlearIX. Glossopharyngeal X. VagusXI. AccessoryXII. Hypoglossal

FUNCTIONAL COMPONENTS

In addition to having similar somatic and visceral components as spinal nerves, some cranial nerves also contain special sensory and motor components

Innervations of the musculature derived from the five pharyngeal arches are

First arch : Trigeminal Nerve Second arch: Facial Nerve Third arch: Glossopharyngeal Nerve Fourth arch: Superior laryngeal branch

of Vagus Sixth arch : Recurrent laryngeal

branch of Vagus

Functional Component

Abbreviation

General Function Cranial Nerves

General Somatic Afferent

GSA Perception of touch, pain, temperature

Trigeminal, Facial, Vagus

General Visceral Afferent

GVA Sensory input from viscera

Glossopharyngeal, Vagus

Special Afferent SA Smell, Taste, Vision, Hearing and Balance

Olfactory, Optic, Facial, Vestibulocochlear, Glossopharyngeal, Vagus

General Somatic Efferent

GSE Motor innervations to skeletal muscles

Oculomotor, trochlear, Abducent, Accessory, Hypoglossal

General Visceral Efferent

GVE Motor innervations to smooth muscles, heart muscles and glands

Oculomotor, facial, glossopharyngeal, vagus

Special Visceral Efferent/ Branchial Motor

BE Motor innervations to skeletal muscles derived from pharyngeal arch mesoderm

Trigeminal, Facial, Glossopharyngeal, Vagus

MOTOR

SENSORY

SENSORY/AFFERENT

OLFACTORY

OPTIC

VESTIBULOCOCHLEAR

I - OLFACTORY NERVE

Special Afferent Smell15-20 pairs of olfactory nerves

Olfactory cells

Nerves pass through the cribriform plate of the ethmoid bone

Olfactory bulb(are prolongation of telencephalon) having mitral cells in

the anterior cranial fossa

Olfactory tract

Olfactory cortex

lateral Olfactory stria

Infro medial surface of the temporal lobe (piriform plate)

II- OPTIC NERVE

Special Afferent Vision It is not a true cranial nerve but

rather an extension of the brain carrying afferent fibres from the eyeball to the visual centres of the brain

Axons of the ganglion cells make up the optic nerve

Optic disk is the central collecting point for these axons

The optic nerve leaves the orbit through optic foramen and then unite with each

other to form the optic chiasma

Fibres from the nasal half cross to the opposite side but the temporal fibres

remain uncrossed

Laterally the termination of ICA is related to the chiasma

Posterior to the chiasma, optic nerves continue as the optical tract

Most of the fibres synapse with the lateral geniculate body in the thalamus

From here some of the fibres go via the optic radiation to the occipital cortex

Those concerned with the pupillary reflex go to the midbrain

Bipolar cells

Optic nerve

Optic Canal

Optic Chiasma

Optic Tract

Lateral Geniculate nucleus

Primary Visual cortex of Occipital Lobe

VISUAL PATHWAY

III- OCULOMOTOR NERVE

General Somatic Efferent

General Visceral Efferent

General somatic afferent Innervates sphincter

pupillae for pupillary constriction and cilliary muscles for accommodation of the lens

Nucleus of this nerve lies in the midbrain(ventromedial part of central gray matter)

Nerve passes between the posterior cerebral and superior cerebral arteries, then passes on the lateral

side of the posterior communicating artery

Nerve enters cavernous sinus by piercing the posterior part of its roof on the lateral side of the posterior

clinoid process

Passes through the sup. orbital fissure into the orbit as upper and lower divisions

This nerve is the motor nerve to Smaller upper division supplies

Levator palpebrae superioris Superior rectus

Larger lower division supplies Inferior rectus Medial rectus Inferior oblique

IV – TROCHLEAR NERVE

General somatic efferent Supplies the superior oblique

muscle Only nerve to exit from the

posterior surface of the brainstem

The nucleus is in the mid brain and the nerve fibres cross midline

It passes forward in the sub-arachnoid space

Pierces the dura mater to lie in the lateral wall

of the cavernous sinus

Nerve enters the orbit through the superior orbital fissure

In the orbit it passes above the origin of the levator palpebrae superiors and ends by supplying the superior rectus on it’s orbital surface

TRIGEMINAL NERVE

Largest cranial nerve Nerve of the first brachial

arch. Small motor root and

large sensory root It has three divisions:1. Opthalmic2. Maxillary 3. Mandibular

TRIGEMINAL NERVE – NUCLEAR ORIGIN There are 4 trigeminal nuclei . One motor and three sensory nuclei.

Exists from the anterolateral surface of the pons as a large sensory root and small motor root

Continues to posterior cranial fossa

Middle cranial fossa by passing over the medial tip of petrous temporal bone

In middle cranial fossa the sensory root expands into trigeminal ganglion which lies in trigeminal depression

The motor root is below and completely separate from the sensory root at this point

Three terminal divisions of trigeminal nerve arise from the ganglion

Ophthalmic, maxillary, mandibular

OPTHALMIC DIVISION

Smallest of the three branches Purely sensory Passes forward in the dura matter of the lateral wall of

cavernous sinus. Leaves the cranial cavity and enters through superior orbital

fissure Supplies

Eyeballs , Lacrimal glands Mucous membrane of nose and paranasal sinuses Skin of the forehead , eyelids, nose.

LACRIMAL BRANCH

Course Passes into orbit at lateral angle of superior orbital fissure Then in anterolateral direction to reach lacrimal gland Zygomatic nerve communicates with lacrimal nerve

Supplies Lacrimal gland Conjunctiva Contents of the eyes Frontal sinus Ethmoidal cells Upper eyelid Dorsum of nose Anterior part of scalp

FRONTAL

The largest branch of the Ophthalmic division. It begins in the lateral wall of the anterior part of the cavernous

sinus. It enters the orbit through the superior orbital fissure, midway between the apex and base of the orbit.

Divides into two branches1. Supratrochlear2. Supraorbital

Supraorbital Passes forward & leaves orbit

through supraorbital foramen Supplies:

Skin of upper eyelid , Forehead , Anterior scalp region to the vertex of skull.

Supratrochlear Passes toward upper medial

angle of orbit Supplies:

Skin of upper eyelid ,Lower medial portion of forehead.

NASOCILLIARY BRANCH OF OPTHALMIC NERVE

Enters orbit through superior orbital fissure. Travels along the medial border of the orbital roof Branches in

Orbit Nasal cavity Face

BRANCHES OF NASOCILLIARY NERVE

Long root of the cilliary ganglion Sensory fibers Pass through ganglion without synapsing Continue on to eyeball

Long cilliary nerves Usually two or three Post ganglionic fibers from superior cervical ganglion Distributed to iris & cornea

Posterior ethmoid nerve Distributed to mucous membrane lining

Posterior ethmoidal cells Sphenoid sinus

Anterior ethmoid nerve Supplies

Anterior and middle ethmoidal cells Frontal sinus

In upper part of nasal cavity divides into Internal nasal branch External nasal branch

MAXILLARY NERVE

Passes forward in the dura matter of the lateral wall of cavernous sinus inferior to the opthalmic nerve

Leaves the cranial cavity through foramen rotundum

Passes through the ptyergopalatine fossa and the inferior orbital fissure

Br. in middle Cranial fossaSingle

branch-Middle

meningeal nerve

Br. in pterygopalati

nefossa

Zygomatic nerve

Pterygopalatine nerve

Posterior superior alveolar nerve

Br. In infraorbital Groove &

canalMiddle

superior alveolar nerve

Anterior superior alveolar nerve

Br. On faceInferior

Palpebral Lateral nasal

Superior labial

THE PTERYGOPALATINE BRANCHES

Branches of Distribution.— Orbital : Periosteum of the orbit Nasal: Superior and middle concha Lining of posterior of

ethmoidal sinus Posterior portion of nasal

septum

ZYGOMATIC BRANCH

Arises in the pterygopalatine fossa

Enters the orbit by the inferior orbital fissure

Divides into two branches, zygomaticotemporal Sensory innervation to skin on the side of forehead zygomaticofacial.Prominence of the cheek

Palate Greater palatine:• Sensory innervations to

palatine soft tissues till the first premolar.

Lesser palatine:• supplies mucous membrane

of the soft palate tonsillar region.

Pharynx• Mucous membrane of the

nasal part of pharynx, posterior to auditory tube.

THE POSTERIOR SUPERIOR ALVEOLAR BRANCHES

Leave maxillary division before entering inferior orbital fissure

Posterior surface of maxilla

Supplies Mucous membrane of

maxillary sinus Maxillary molar &

gingiva

THE MIDDLE SUPERIOR ALVEOLAR BRANCH

Leaves the maxillary nerve in posterior part of infraorbital canal

Downward & anteriorly toward apices of maxillary bicuspids

Supplies 1. Maxillary bicuspids2. Mesiobuccal root of

maxillary 1st molar

THE ANTERIOR SUPERIOR ALVEOLAR BRANCH

Descends from infraorbital nerve inside infraorbital foramen in anterior part on infraorbital canal.

Supplies Central incisors Lateral incisors Cuspid teeth

BRANCHES ON THE FACE The Inferior Palpebral Branches Skin and conjunctiva of the lower

eyelid

The External Nasal Branches The skin of the side of the nose.

The Superior Labial Branches Skin & mucous membrane of

upper lip.

MANDIBULAR NERVE

Leaves the inferior margin of trigeminal ganglion

Leaves the skull through the foramen ovale.

The motor root also passes through the foramen ovale.

Unites with sensory component of mandibular nerve outside the skull

•Meningeal •Nerve to medial pterygoidTrunk•Deep temporal•Lateral pterygoid•Massetric•Buccal

Anterior division

•Auriculotemporal •Lingual •Inferior alveolar

Posterior division

MENINGEAL BRANCH

Given off just after union of sensory & motor root.

Enter foramen spinosum

Accompanies middle meningeal artery

Supplies dura mater of middle cranial fossa

Supplies medial pterygoid

Branch to a. Otic ganglionb. Tensor tympanic. Tensor veli palatini

Nerve to medial pterygoid

Nerve to lateral pterygoid: Supplies lateral pterygoid muscle Masseter nerve Passes above lateral pterygoid & enter

masseter muscle Deep temporal nerveAnterior, middle & posterior deep temporal nerves Pass upwards to reach deep surface of

temporalis Buccal nerve Anteriorly & laterally between two heads

of lateral pterygoid.At about the level of 2nd & 3rd molar.

ANTERIOR DIVISION

AURICULOTEMPORAL NERVE

Arises by two roots which form a ring through middle meningeal artery passes.

Backward in infratemporal fossa & crosses neck of mandible laterally behind TMJ

Branches1. Auricular2. Superficial temporal3. Auricular or TMJ4. Secretomotor to Parotid

Smaller of two branches of posterior division

Passes medially to lateral pterygoid muscle

Lies parallel to inferior alveolar nerve

Passes deep, reach side of the base of tongue.

Passes forward, loops downward & medially beneath submandibular duct.

Lingual nerve

As lingual nerve passes medially to external pterygoid, it is joined by chorda tympani nerve.

It supplies:i. Mucous membrane of the floor of the mouth.ii. Gingiva on the lingual of the mandible. Convey Secretory fibers Lingual nerve carry three type of fibers Fiber for ordinary sensation Fibers for taste Secretomotor fibers

INFERIOR ALVEOLAR NERVEPasses downward on medial side of lateral pterygoid & mandibular ramus

In mandibular foramen, descends & distributed throughout mandibleBranches to mandibular teeth & reach mental foramen

Two terminal branches, Mental nerve& incisive nerve leave through mental foramen

VI – ABDUCENS NERVE

General somatic efferent and afferent Supplies the lateral rectus muscle

Arises from the brain stem between the pons and medulla

It passes upward forward and laterally through the cisterna pontis to reach the cavernous

sinus

Lying at first lateral then infero lateral to the Internal carotid artery

Nerve enters the orbit through the medial part of superior orbital fissure

Ends by supplying the lateral rectus muscle ocular surface

VII - FACIAL NERVE General somatic

afferent Special visceral

afferent General visceral

afferent Special visceral

efferent General visceral

efferent

Sensory supply to parts of external acoustic meatus and deeper part of auricle

Special taste sensation from anterior two third of the tongue

Parasympathetic supply to lacrimal gland, sub mandibular and sublingual salivary glands, mucous membranes of the nasal cavity, hard and soft palate

Motor innervation to muscles of facial expression, scalp ( derived from the second arch)

stapedius posterior belly of digastric stylohyoid muscles

Facial nerve is attached to the lateral surface of the brain stem, between

pons and medulla

Consists of larger motor root and small sensory root ( intermediate nerve)

They leave the cranial cavity through the internal acoustic meatus

Facial nerve is closely associated with the vestibulocochlear nerve

The two roots fuse and enters the facial canal in the petrous temporal bone

Near this point the nerve enlarges as the geniculate ganglion

It gives of the greater petrosal nerve at this bend

Facial nerve continues along the bony canal

Gives off the nerve to stapedius and chorda tympani before exiting the skull

through the stylomastoid foramen

Within the facial canal Greater petrosal

nerve(supply the secretomotor fibers to lacrimal gland and mucous glands of nasal cavity and palate.)

Nerve to stapedius supplies the stapedius muscle Chorda tympani

Consist two types of fibers i. Preganglionic parasympathetic (GVE)

fibers, provides secretomotor supply to submandibular

& sublingual glands.

ii.Special viseral afferant fibers

carries taste sensation from ant. 2/3 of the tongue.

At it’s exit from the stylomastoid foramen Posterior auricular

Auricularis posterior Occipitalis Intrinsic muscle of the back of

the auricle Digastric

Post. Belly of digastric Stylohyoid

Stylohyoid muscles

Terminal branches within the parotid gland Temporal Zygomatic Buccal Marginal mandibular Cervical

Communicating branches to

adjacent cranial and spinal nerves

Temporal Brancho Auricularis anterioro Auricularis superioro Frontaliso Orbicularis oriso Corrugator supercilli

Zygomatic: Orbicularis oris

Marginal mandibular Muscles of lower lip and chin

Cervical branch Platysma

VIII –VESTIBULOCOCHLEAR NERVE Special

Afferent Hearing and

balance Vestibular

component for balance

Cochlear component for hearing

After emerging from the internal acoustic meatus it crosses the posterior cranial fossa within the substance of the petrous part of temporal bone

The nerve attaches to the lateral surface of the brainstem, between pons and medulla

It is closely associated with the facial nerve

Vestibular ganglia (consist of bipolar sensory neurons)

divides in 3 distinct branches Superior, inferior & singular nerve

innervates the sensory receptor for equilibrium(cristae ampullaris and maculae)in membranous labyrinth of int. ear.

The cochlear nerve ganglion is called spiral ganglion & innervates the sensory receptor of hearing – the organ of Corti.

IX – GLOSSOPHARYNGEAL NERVE

General somatic afferent

Special visceral afferent

General visceral afferent

General visceral efferent

Special visceral efferent

Motor supply to stylopharyngeus

Secretomotor to parotid gland

Gustatory to post. one third of tongue

Sensory to pharynx, tonsil, soft palate, post. one third of tongue, carotid body and carotid sinus

Arises as several rootlets on the anterolateral surface of the upper medulla oblongata

The rootlets cross the posterior cranial fossaEnter the jugular foramen

Merge to form glossopharyngeal nerve before exiting from jugular foramen

Within or immediately outside jugular foramen are superior and inferior ganglia

In the jugular foramen the nerve is lodged in the deep groove and is separated from vagus and accessory nerves.

Outside the foramen it passes forward between the internal jugular vein and internal carotid artery.

It turns forward winding round the lateral aspect of stylopharyngeus (passes between external and internal

carotid artery)reaches the pharynx and gives away pharyngeal branches.

It enters the submandibular region by passing deep to hyoglossus and divides into tonsillar and lingual branches.

Tympanic branch (jacobson’s nerve) Secretomotor supply of

parotid gland and other small glands in the vestibule of the mouth

Motor branch: stylopharyngeus:

Carotid sinus nerve: carotid sinus & body

Pharyngeal branches: Mucous membrane and serous glands of oropharynx Taste fibres

Tonsillar branch: Mucous membrane of the palatine tonsil & palate

Lingual Posterior one third of the tongue taste & general

sensation

X – VAGUS NERVE

General somatic afferent

Special visceral afferent

General visceral afferent

General visceral efferent

Special visceral efferent

Sensory supply to larynx, laryngopharynx, deeper part of auricle, part of external acoustic meatus and dura in the posterior cranial fossa

Sensory from aortic body chemoreceptors and aortic arch baroreceptors, esophagus, bronchi, lungs, heart, and abdominal viscera of foregut and midgut

Taste from epiglottis and pharynx Innervates the smooth muscles and

glands in the pharynx, larynx, thoracic viscera and abdominal viscera of the foregut and midgut

Innervates palatoglossus, muscles of soft palate ( except tensor veli palatini), pharynx ( except stylopharyngeus) and larynx

Vagus nerve arises as a group of rootlets on the anterolateral surface of the medulla oblongata just inferior to the rootlets arising to form the glossopharyngeal nerve

Rootlets enter the jugular foramen

In the foramen they merge to form one fibre

Leaves the cranial cavity by passing through the middle of the jugular foramen

The nerve descends within the carotid sheath in between and posterior to the internal jugular vein and common and internal carotid artery

Right vagus enters the thorax by crossing the first part of sub clavian artery and inclining medially behind the brachiocephalic vessels

Left vagus enters by passing between the left common carotid and left sub clavian arteries behind internal jugular and brachiocephalic veins

Vagus bears two ganglia

Superior Lies in the jugular

foramen Inferior

Lies below the base of the skull

Formed where accessory portion of the spinal accessory joins the vagus

Branches Superior ganglion, in the jugular foramen

Meningeal : Supplies dura of the posterior cranial fossa

Auricular : Supplies concha, root of the auricle, posterior half of external auditory meatus and the tympanic membrane

Communicating branches to the glossopharyngeal and cranial roots of accessory nerve

Inferior ganglion in the neck Pharyngeal : forms the pharyngeal plexus

and supplies the muscles of the pharynx and soft palate

Carotid : supplies the carotid body and sinus Sup. Laryngeal

External : supplies cricothyroid, branches to inferior constrictor and to the pharyngeal plexus

Internal : Supplies the mucous membrane of the larynx upto the vocal folds

Recurrent laryngeal Intrinsic muscles of

larynx except cricothyroid

Sensory nerves to larynx below the level of vocal chords

Cardiac branches to deep cardiac plexus

To trachea and oesophagus

To inferior constrictor

Cardiac branches They go to the

superficial cardiac plexus and the deep cardiac plexus

XI – ACCESSORY NERVE General somatic

efferent It has two roots :

cranial and spinal Cranial root is

accessory to vagus Motor root arise

from the motor neurons of the upper segments of cervical spinal cord

Spinal root supplies the sternocleidomastoid muscle and trapezius muscle

Cranial root is distributed through the branches of vagus to the muscles of palate( except tensor palati & tympani)

All intrinsic muscle of larynx All pharynx muscle except

stylopharangeus

The cranial roots emerge from posterolateral sulcus of the medulla

In the jugular foramen the cranial root briefly unites with the cervical root and again separates as it passes out of the foramen

Cranial nerve fuses with the vagus and the inferior ganglion and is distributed through the branches of the vagus

The cervical roots unite to form a single trunk in the vertebral canal and enter the cranium through foramen magnum

Along with glossoparyngeal and vagus it reaches the jugular foramen

It leaves the skull through the middle part of the jugular foramen

Extracranially the nerve descends vertically between internal jugular vein and internal carotid artery deep to the parotid and to the styloid process

Then it runs downwards and backwards superficial to the internal jugular vein and deep to the SCM

XII – HYPOGLOSSAL NERVE

General somatic efferent

Supplies the all intrinsic and extrinsic ( except palatoglossus) of the tongue

It arises from the anterior surface of the medulla,

Passes laterally across the posterior cranial fossa and exists through the hypoglossal canal

It first lies deep to the internal jugular vein then crosses the vagus laterally and reaches in

front

It descends downwards to the lower border of the posterior belly of digastric

It curves forward, hooks around the lower sternocleidomastoid branch of occipital artery, crosses the ICA and ECA and the loop of lingual artery and passes deep to post belly of digastric to enter the submandibular region

Nerve then continues forward on the hyoglossus and genioglossus, enters the substance of the tongue to supply the muscles

BRANCHES

Meningeal branch

Styloglossus Hypoglossus Genioglossus Geniohyoid Thyrohyoid

It supplies the extrinsic muscles Styloglossus Genioglossus Hyoglossus

Intrinsic muscles Superior longitudinal Inferior longitudinal Transverse Vertical

Conclusion

Reference Lee McGregor’s Surgical Anatomy Grey’s Anatomy Sicher and DuBrul’s Oral anatomy B D Chaurasia’s Human Anatomy(5TH

edition) Vishram singh 2nd edition Internet