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