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Cranial Nerves


There are 12 pairs of cranial nerves I (olfactory), II (optic), III (oculomotor), IV(trochlear), V (trigeminal), VI (abducent), VII (facial), VIII (vestibulocochlear), IX (glossopharyngeal), X (vagus), XI (accessory) and XII (hypoglossal). Attachment of nerves are; I and II to forebrain; III and IV to midbrain; V, VI, VII and VIII to pons; and IX, X, Xland XII to medulla.


Cranial Nerve Nuclei

  1. There are mainly two types of nuclei of cranial nerves i-
    1. Efferent nuclei (motor nuclei or nuclei of origin):- These are groups of neurons in brain from which the nerve fibers arise. And then the nerve supplies specific motor organ (gland, muscles etc.).
    2. Afferent nuclei (sensory nuclei or nuclei of termination):- These are the nuclei to which cranial nerve carry sensation from peripheral organs.
  2. Based on the type of efferent organ supplied by the nerve and/or sensory organ from which the nerve carries sensation, these two types (efferent and afferent) of nuclei are divided into following types ;-

Efferent nuclei (Motor nuclei)

  1. General somatic efferent nuclei: - These nuclei supply skeletal muscles of somatic origin. These are i-
    1. Oculomotor nucleus: - It lies in upper mid brain (near superior colliculus) and supplies extraocular muscles (except for lateral rectus and superior oblique) through oculomotor nerve.
    2. Trochlear nucleus: - It lies in lower mid brain (near inferior colliculus) and supplies superior oblique through trochlear nerve.
    3. Abducent nucleus: - It lies in pons (lower part) and supplies lateral rectus through abducent nerve.
    4. Hypoglossal nucleus:-It lies in medulla and through hypoglossal nerve supplies muscles of tongue, except palatoglossus.
  2. Special visceral efferent (Branchial efferent) nuclei: - These nuclei supply skeletal (striated) muscles derived from the branchial arches. These are ;-
    1. Motor nucleus of trigeminal: - It lies in upper pons and supplies muscles of mastication and tensor tympani through mandibular nerve.
    2. Motor nucleus of facial nerve:-It lies in lower pons and supplies muscles of facial expression, alatees and stapedius.
    3. Nucleus ambiguous:Its fibers are distributed through three cranial nerves; glossopharyngeal , Vagus and accessory (XI) The destination is
      1. To stylopharyngeus through glossopharyngeal.
      2. To muscles of soft palate (except tenser veli alatee), pharynx (except stylopharyngeus) and larynx throughvagus and cranial part of accessory nerve.
  3. General visceral efferent nuclei (parasympathetic):- These nuclei give origin to preganglionic parasympathetic neuronsthat relay in peripheral autonomic ganglion. Postganglionic fibers arising in the ganglion supply smooth muscles and glands. These are ;-
    1. Edinger-westphal nucleus in the midbrain – fibres passes through the 3rd nerve to the ciliary ganglion to supply the sphincter alatee and ciliary muscle.
    2. Lacrimatory nucleus in the pons – fibres pass through facial nerve and its greater petrosal nerve to relaying the pterygopalatine ganglion to supply lacrimal, nasal and palatal glands.
    3. Superior salivatory nucleus in lower pons – fibres pass through facial nerve and its chorda tympani branch to the submandibular ganglion to supply submandibular and sublingual glands.
    4. Inferior salivatory nucleus in lower pons – fibres pass through glossopharyngeal nerve to relay in theotic ganglion to supply parotid gland.
    5. Dorsal nucleus of vagus in medulla – fibres pass through vagus nerve to be distributed to the thoracic and abdominal viscera through respective ganglia.

Afferent nuclei (Sensory nuclei)

  1. General visceral afferent nucleus: - It receives general sensations from viscera. This nucleus is ; Nucleus of tractus alatees: - It lies in medulla and its lower part receives general visceral sensations asfollows – From tonsil, pharynx, posterior part of tongue, carotid body and sinus through glossopharyngeal nerve. From pharynx, larynx, trachea, esophagus, and other thoracic and abdominal viscera through vagus nerve.
  2. Special visceral afferent nucleus: - It receives sensations of taste (special visceral sensations). This nucleus is Nucleus of tractus alatees: - It is the same nucleus as for general visceral afferent. Its upper part receives taste sensations (lower part receives general visceral sensations):-
    1. From anterior 2/3 of tongue (except circumvallate papillae) and palate through facial nerve.
    2. From posterior 113 of tongue (including circumvallate papillae) through glossopharyngeal nerve.
    3. From posterior most part of tongue and epiglottis through vagus nerve.
  3. General somatic afferent nuclei :- These nuclei receives general somatic sensations (pain, touch) and temperature sensations from face and proprioception from muscles of mastication, face and from TM joint and all related to trigeminal nerve. These nuclei are:-
    1. Main sensory nucleus of trigeminal (superior sensory nucleus:-Lies in upper pons for fine touch from face.
    2. Spinal nucleus of trigeminal: - It descends from main sensory nucleus of pons into medulla and reaches the upper two segments of spinal card for pain and temperature from face through trigeminal.
    3. Mesencephalic nucleus of trigeminal: - It extends from main sensory nucleus of pons into midbrainfor proprioception from muscles of mastication through trigeminal.

Important facts

These three nuclei of trigeminal nerve also receive inputs from other nerves (beside trigeminal) :-

  1. Mesencephalic nucleus receives proprioceptive impulses (beside from muscles of mastication through trigeminal) :-
    1. From extraocular muscles (except SO and LR) through oculomotor nerve.
    2. From superior oblique through trochlear nerve.         
    3. From lateral rectus through abducent nerve.
    4. From stylopharyngeus through glossopharyngeal nerve.
    5. From muscles of face through facial nerve.
    6. From muscles of tongue through hypoglossal nerve.
  2. Spinal nucleus receives exteroceptive sensations i.e., of touch, pain, temperature (beside from face through trigeminal) from:-
    1. Skin of ear through vagus (auricular branch).
    2. Skin of ear through facial nerve.
    3. Middle ear through glossopharyngeal nerve.

  1. Special somatic afferent nuclei :- These nuclei receive special somatic sensations (hearing and equilibrium) as follows :-
    1. Cochlear nuclei (dorsal and ventral):- These lie at junction of pons and medulla, and receive impulses of hearing through Cochlear nerve (Cochlear division ofvestibulocochlear nerve).
    2. Vestibular nuclei (superior, spinal, medial, and lateral:-These lie at junction of pons and medulla that receive sense of equilibrium from semi-circular canal, utricle and saccule through vestibular nerve (vestibular division of vestibulocochlear nerve).

Olfactory (I) Nerve


Olfactory nerve is a special visceral afferent nerve that mediates sense of smell (olfaction). Olfactory nerve has following unique features:-

  1. The primary olfactory neurons lie at the body surface in the epithelium lining the roof of nasal cavity (olfactory epithelium).
  2. The primary olfactory neurons undergo continuous turnover being replaced from stem cells in the olfactory epithelium. No other neuron in the nervous system is replaced from stem cells.
  3. It is the only cranial nerve that projects directly to forebrain (telencephalon).
  4. The olfactory neurons enter the allocrotex directly without relaying through thalamus. In all other sensory systems, fibers relay through thalamus before projecting to cerebral cortex.
  5. The olfactory pathway to highest cortical center is ipsilateral. All other sensory pathways have mainly or entirely crossed cortical representation.




  1. Optic nerve is a special somatic afferent nerve that subserves vision and form afferent limb of papillary and accommodation reflexes.
  2. Each optic nerve (second cranial nerve) starts from the optic disc and extends up to optic chiasma, where the two nerves meet. It is the backward continuation of the nerve fibre layer of the retina, which consists of the second order neurons i.e., axon originating from the ganglion cells. It also contains the afferent fibres of the alatee light reflex. Morphologically and embryologically, the optic nerve is comparable to a sensory tract. Unlike peripheral nerves it is not covered by neurilemma (so it does not regenerate when cut). The fibres of optic nerve, numbering about a million , are very fine (2-10 m in diameter as compared to 20 mm of sensory nerves).
  3. Optic nerve is about 47-50 mm in length and can be divided into 4 parts; -
    1. Intraocular part (1 mm): -It begins at optic disc (optic nerve head) and exits the nerve through a hole in sclera that is occupied by a mesh like structure called the lamina cribrosa. The nerve fibres from the retina leave the eye through pores (holes) in lamina cribrosa, a sieve-like structure made up of collagen meshwork.
    2. Intraorbital part (30 mm): - Extends from back of the eyeball (at lamina cribrosa) to the optic foramina.
    3. Intracanalicular part (6-9 mm): -It lies within the optic canal and closely related to ophthalmic artery which crosses obliquely over it.
    4. Intracranial part (10 mm); -It lies above the cavernous sinus and converges with its fellow from contralateral side to form optic chiasma.
  4. Like other parts ofCNS, the optic nerve is covered by meningeal sheaths (Pia, arachnoid and dura mater) as soon as the nerve leaves the eyeball.


Oculomotor (III) Nerve

  1. This is purely motor (somatic motor) nerve. It has following functional components ;-
    1. General somatic efferent): Through oculomotor nucleus for movement of eyeball supplying all extraocular muscles except SO and LR.
    2. General visceral efferent (parasympathetic):- Through Edinger-Westphal nucleus for alatee contraction and accommodation.
    3. General somatic afferent: - Carries proprioceptive fibres from the extraocular muscles to Mesencephalic nucleus of trigeminal.
  2. Oculomotor nucleus (for general somatic efferent) and Edinger- Westphal nucleus together form oculomotor nuclear complex.
  3. Oculomotor nerve descends to the lateral wall of cavernous sinus and in the anterior part of sinus it divides, into upper (superior) and lower (inferior) divisions, which enter the orbit through middle part of superior orbital fissure.
    1. An upper (superior) division is smaller and supplies superior rectus and levator palpebrae superioris.
    2. Lower (inferior) division is larger and supplies inferior oblique, inferior rectus, and medial rectus. Nerve to inferior oblique is the longest of these and gives of parasympathetic root to ciliary ganglion before supplying the muscle.
  4. All branches enter extraocular muscles and their ocular surfaces except for inferior oblique which enters its posterior border.

Features of 3rd (occulomotor) nerve palsy

  1. Paralysis of superior rectus, inferior rectus, medial rectus and inferior oblique. Eye is down and out due to unopposed action of superior oblique and lateral rectus. Medial & upward gaze is not possible.
  2. Paralysis ofsphincter alatee: Loss ofipsilateral direct and consensual alatee light reflex and there is mydriasis.
  3. Paralysis of ciliary muscle: Paralysis of accommodation and conversion reaction.
  4. Two extraocular muscles are spared
    1. Superior oblique: - Intorsion, abduction and depression remain active.
    2. Lateral rectus:-Abduction remains active. So eye is deviated laterally.
  5. Paralysis of levator palpebrae superioris:Ptosis.
  6. Oculomotor nerve is the most commonly involved cranial nerve in intracranial aneurysm.


Trochlear (IV NERVE)

  1. Trochlear nerve is a pure motor (somatic motor) nerve. Its functional components are :-
    1. General somatic efferent):- Through trochlear nucleus for contraction of superior oblique.
    2.  General somatic afferent: - Carries proprioceptive fibers from superior oblique to mesencephalic nucleus of trigeminal.
  2. Unique features of trochlear nerve are ;-
    1. Most slender cranial nerve.
    2. Only
    3. Only cranial nerve to undergo complete internal decussation before emerging i.e. right trochlear nerve arises from left trochlear nucleus and vice versa.
    4. Has longest intracranial courser(Vagus nerve has overall longest course)
  3.  Trochlear nerve enters the orbit through superior orbital fissure outside the annulus of Zinn.



Abducent (VI) Nerve

  1. Abducent nerve is pure motor (somatic motor) nerve. It has following functional components-
    1. General somatic efferent: - Through abducent nucleus for contraction oflateral rectus.
    2. General somatic afferent: - Carries proprioceptive impulses from lateral rectus to mesencephalic nucleus of Nerve.
  2. Abducent nerve is the most commonly involved nerve in increased intracranial tension and in spinal anaesthesia.
  3. At petrous apex, abducent nerve makes a sharp bend to pass through Dorello’s canal beneath Gruber’s ligament




Trigeminal (V) Nerve


  1. Trigeminal nerve is the nerve of 1STbranchial arch. It is the largest (thickest) cranial nerve. It is a mixed nerve (sensory component is more prominent). It supplies its target organs through its three branches ophthalmic (first division: VI) maxillary (second division: V), and mandibular (third division: V3). First two branches are purely sensory, and third branch is mixed nerve and is the largest branch. Branches of trigeminal also provide sensory fibers to four parasympathetic ganglia; ciliary ganglion, pterygopalatine ganglion, Otic ganglion and submandibular ganglion.
  2. Functional components of nerve are ;-
    1. General somatic afferent: - These fibers terminate in three sensory nuclei of trigeminal; the mesencephalic, the main sensory, and the spinal nuclei. These sensory fibers (general somatic afferent) arise from ‘pseudounipolar neurons’ of trigeminal ganglion. The peripheral process of these neurons of trigeminal ganglion form three divisions (ophthalmic, maxillary, and mandibular) of trigeminal nerve and provide sensory alateess to eyeball, face, auricle, scalp, mucous membrane of nasal cavity, oral cavity, paranasal sinuses, teeth, and dura mater of anterior and middle cranial fossae.
    2. The central process of pseudo unipolar neurons of trigeminal ganglion forms the sensory root of trigeminal nerve which enter the various nucleus of trigeminal :-
      1. Main (principal) sensory nucleus (superior sensory nucleus):-Receives sensory fibers of fine touch and pressure from face.
      2. Spinal nucleus:-Receives sensory fibers of pain and temperature from face. Beside trigeminal nerve, spinal nucleus also receives sensory inputs (general somatic afferents) from facial nerve (skin of ear), glossopharyngeal (middle ear), and auricular branch of vagus (skin of ear).
      3. Mesencephalic nucleus:-Receives proprioceptive fibers from muscles of mastication and temporomandibular joint. Besides trigeminal nerve this nucleus also receives proprioceptive inputs by III, IV, VI cranial nerves (from extraocular muscles); IX nerve (from stylopharyngeus); VII nerve (from facial muscles); and from XII nerve (from muscles of tongue).
  3. Special visceral efferent (branchial efferent):- For muscles of mastication, tensor veli alatee, tensor tympani and anterior belly of alatees, though motor nucleus of trigeminal.

Thus, trigeminal nerve has four nuclei:-3 sensory and one motor

Trigeminal ganglion (Gasserion ganglion or semilunar ganglion)

Trigeminal ganglion lies in a dural pouch, the cavum trigeminale (Meckel’s Cave) lodged in the trigeminal impression close to petrous apex. Peripheral process of pseudounipolar neurons of ganglion forms the three divisions of nerves and central process of these neurons form the sensory root of trigeminal nerve. Blood supply of ganglion is from; internal carotid artery, middle meningeal artery, accessory meningeal artery and meningeal branch of ascending pharyngeal artery.


Divisions of trigeminal nerve

Trigeminal nerve has following divisions:-


Ophthalmic division

Ophthalmic nerve is pure sensory nerve. It divides into following branches:-

  1. Frontal Nerve :- It divides into following branches :-
    1. Supratrochlear: Supplies upper eyelid, conjunctiva and lower part of forehead.
    2. Supraorbital: Supplies frontal sinus, upper eyelid, forehead, and scalp till vertex.
  2. Lacrimal Nerve: - It supplies skin oflateral half of upper eyelid. It also conveys postganglionic secretomotor fibers for lacrimal gland after joining by a communicating branch from zygomaticotemporal branch of maxillary nerve.
  3. Nasociliary Nerve:- It gives:-
    1. Sensory root to ciliary ganglion.
    2. Long ciliary nerves: Sensory to eyeball.
    3. Posterior ethmoidal nerve: Supplies sphenoidal and posterior ethmoidal sinuses.
    4. Infratrochlear nerve: Supplies both eyelids, side of nose, lacrimal sac.
    5. Anterior ethmoidal nerve: Supplies middle and anterior ethmoidal air sinuses, interior of nasal cavity (anterosuperior part of nasal septum and lateral nasal wall by internal nasal branches), anterior cranial fossa and skin of nose up to its tip (by external nasal branch).

Maxillary division (Maxillary nerve: V2)

It is pure sensory nerve. It enters the pterygopalatine fossa through foramen rotundum. Then enters the floor of through inferior orbital fissure and continues as infraorbital nerve. Its branches are: -

  1. In middle cranial fossa:-Meningeal branch supplies dura mater of middle and anterior cranial fossa.
  2. In pterygopalatine fossa :- Branches are : -
    1. Ganglionic branches
    2. Zygomatic branch divides into two sensory branches:Zygomaticotemporal and zygomaticofacial.
    3. Posterior superior alveolar nerve: supplies posterior wall of maxillary sinus, upper molar teeth and adjacent gums.
  3. In infraorbital canal :- Continuation of maxillary nerve in this canal is called infraorbital nerve which gives :-
    1. Middle superior alveolar nerve: Supplies lateral wall of maxillary sinus and upper premolar teeth.
    2. Anterior superior alveolar nerve: Supplies anteroinferior part of lateral wall of nose, maxillary sinus, and upper canine and incisor teeth.
  4. On face :- Continuation of maxillary nerve in infraorbital canal is called as infraorbital nerve which emerges in the face through infraorbital foramen and divides into three branches :-
    1. Palpebral Supplies skin of lower eyelid.
    2. Labial : Supplies skin of upper lip.
    3. Nasal. : Supplies skin of ala and vestibule of nose.

Mandibular division (Mandibular nerve: V 3)

It is mixed nerve. Mandibular (sensory fibers) of trigeminal ganglion and motor root of trigeminal nerve enter foramen ovale where they join to form mandibular nerve, and leave the skull through foramen ovale to enter infratemporal fossa. Mandibular nerve is the largest division of trigeminal nerve. Branches of mandibular nerve are:-

From main trunk

  • Branches from main trunk are :-
  1. Meningeal branch (nervous spinosum):- Passes through foramen spinosum to supply dura mater of middle cranial fossa.
  2. Nerve to medial pterygoid:-It supplies medial pterygoid. It also supplies tensor tympani and tensor veli alatee through otic ganglion.

From anterior division

It is mainly motorand gives following branches:-

  1. Nerve to masseter, supplies masseter.
  2. Deep temporal nerve supplies temporalis.
  3. Nerve to lateral pterygoid supplies lateral pterygoid.
  4. Buccal sensory branch supplies skin over alatees, mucous membrane of cheek, vestibule of mouth.

From posterior division

It is mainly sensory and gives following branches:-

  1. Auriculotemporal nerve:-It receives postganglionic secretomotor fibers from otic ganglion which supply parotid gland. It also supplies temporomandibular joint, lateral surface of auricle, and anteroinferior wall of external acoustic meatus.
  2. Inferior alveolar nerve:- It supplies lower teeth (molar, premolar, canine, and incisors), skin of chin (by mental branch) and gives nerve to mylohyoid which supplies mylohyoid and anterior belly of alatees.
  3. Lingual nerve: It is joined by chorda tympani branch of facial nerve, conveying secretomotor fibers for submandibular gland and taste sensory fibers from anterior two third of tongue. It grooves the medial aspect of socket for lower 3rd molar, runs forward over hyoglossus muscle and loops around submandibular duct to reach inferior surface of tongue. It supplies mucosa of anterior 2/3 of tongue, floor of mouth and inner gums of lower teeth.

Clinical anatomy of tri2eminal nerve

  1. Corneal reflex:-Afferent limb is formed by ophthalmic nerve and efferent limb is facial nerve. Cornea ~ Ophthalmic nerve ~ Spinal nucleus of trigeminal ~ Motor nucleus of facial nerve ~ Facial nerve ~ Orbicularis oculi.
  2. Jaw jerk (Masseteric reflex):- Both afferent and efferent limbs are formed by mandibular nerve. Muscle spindle in masseter ~ mandibular nerve ~ mesencephalic nucleus of trigeminal~ motor nucleus of trigeminal ~ mandibular nerve ~ masseter.
  3. Sneezing reflex: - Afferent limb is formed by maxillary nerve.
  4. Lacrimal reflex: - Ophthalic nerve forms afferent limb and facial nerve forms efferent limb.
  5. Oculocardiac reflex: - Ophthalmic nerve is afferent limb and vagus nerve is efferent limb.
  6. Motor examination of trigeminal nerve can be done by:-
    1. On clenching of teeth, the temporalis and masseter muscles become prominent and can be felt. It trigeminal nerve injury, these muscles do not become prominent.
    2. On opening ofmouth,jaw is deviated to affected side in trigeminal nerve injury as the normal side lateral pterygoid muscle pushes the jaw to opposite side.
    3. There may be hollowing of temporal fossa due to wasting of temporalis.
    4. Sensory deficit in trigeminal nerve injury results in loss of pain, temperature and touch sensations in face.

Facial (VII) Nerve

Facial nerve is the nerve of 2ndpharyngeal arch. Facial nerve is a mixed nerve and consists of a motor and a sensory root. Sensory part is frequently described under the name of nervous intermedius (nerve of Wrisberg). Functional components and nuclei of facial nerve are:-

  1. Special visceral (branchial) efferent: Through motor nucleus of facial nerve for muscles of 2ndarch (muscles of facial expression, occipitofrontalis, platysma, stapedius, stylohyoid, posterior belly of alatees).
  2. General visceral efferent (parasympathetic): Parasympathetic secretomotor fibers arise from lacrimatory and superior salivatory nuclei, and supply lacrimal, nasal, palatine, submandibular and sublingual glands, after relay in pterygopalatine and submandibular ganglia.
  3. General visceral afferent: Lower part of nucleus tractus alatees receives afferent impulses from above mentioned glands.
  4. Special visceral afferent: Upper part of nucleus tractus alatees receives taste sensation from palate and anterior 2/3 of tongue except from vallate papillae.
  5. General somatic afferent: Sensory fibers from skin of auricle reach spinal nucleus of V nerve and proprioceptive impulses from facial muscles travel through branches of trigeminal nerve to reach the mesencephalic nucleus of V nerve.


Course of facial nerve

The facial nerve is attached to brainstem by two roots, motor root and sensory root (nervus intermedius or nerve of Wrisberg),The course of facial nerve is divided into: -   

  1. Intracranial part (15-20 mm)
    1. Motor and sensory roots exit at the cerebellopontine angle in posterior cranial fossa and enter internal acoustic meatus along with VIII cranial nerve and labyrinthine vessels.
  2. Intrameatal part (8-10 mm)
    1. Sensory and motor roots traverse separately in the meatus along with VIII nerve and labyrinthine vessels. The motor root lies in a groove on the eighth nerve, with sensory root intervening. At the bottom (fundus) of meatus, sensory and motor roots fuse to form single nerve which lies in petrous temporal bone.
  3. Intratemporal part
    It is the part of nerve from internal acoustic meatus to stylomastoid foramen. The nerve travels through petrous temporal bone in a bony canal called the fallopian canal. No other nerve in the body travels such a long distance through a bony canal. Because of this bony shell around the nerve, inflammatory process involving the CNS or facial nerve, and traumatic injury to the temporal bone can produce unique complications.
    This part of facial nerve is subdivided into: -
    1. Proximal or labyrinthine segment (3-5 mm)
      The labyrinthine segment lies beneath the middle cranial fossa and is the shortest segment in the fallopian canal. The nerve is directed obliquely forward, perpendicular to the axis of temporal bone. The labyrinthine segment is the narrowest part of facial nerve and therefore is most susceptible tocompression by means of oedema. This is the only segment of facial nerve that lacks anastomosing arterial cascades, making the area vulnerable to embolic phenomenon, low-flow states, or vascular compression. After traversing the labyrinthine segment, the nerve changes its direction to form the first genu, marking the location of geniculate ganglion, and to become tympanic segment. So, this segment extends from internal acoustic meatus to geniculate ganglion.
    2. Tympanic or horizontal segment(8-12 mm)
      This segment extends from the geniculate ganglion to the horizontal semi-circular canal just above the pyramidal eminence. The nerve passes behind the cochleariform process and cochleariform process is a useful landmark for finding facial nerve. The wall can be very thin or dehiscent in this area; therefore tympanic segment is most susceptible to injury during surgery and maximum bony dehiscence occurring in this part adjacent to oval window. Just distal to the pyramidal eminence, facial nerve makes a second turn marking the second genu and becomes the mastoid segment.
    3. Mastoid or vertical or descending segment (9-16 mm)
      The second genu marks the beginning of mastoid segment and the nerve continues vertically down the anterior wall of the mastoid process to the stylomastoid foramen. Mastoid segment is the longest part of the intratemporal course of the facial nerve.
  4. Extratemporal part
    The facial nerve exits the fallopian canal via the stylomastoid foramen. The nerve travels between the digastricand stylohyoid muscles and enters the parotid gland where it divides into its peripheral branches.

Branches of facial nerve

Facial nerve is a mixed nerve, i.e., has both motor as well as sensory fibers. Motor part supplies the muscles of theface, scalp, and auricle; the Buccinator and platysma; the stapedius; the stylohyoid; and posterior belly of alatees. Sensory part contains the fibers of taste for the anterior two third of the tongue and a few somatic sensory fibers from the middle ear region. The branches of facial nerve are: -

  1. In the fallopian canal (from intratemporal part)
    Intratemporal part gives following branches: -
    1. Greater superficial petrosal nerve: - It is the first branch and arises from geniculate ganglion (i.e., first genu). It joins the deep petrosal nerve to form Vidiannerve (nerve to pterygoid canal) and carries secretomotor fibres to the lacrimal gland, nasal gland, Palate gland and pharyngeal gland after relaying in pterygopalatine ganglion.
    2. Nerve to stapedius: - It is the second branch of facial nerve and arises at the level of second genu.It supplies the stapedius muscle and its damage can cause hyperacusis.
    3. Chorda tympani:It arises from the middle of vertical segment. It carries : (i)submandibular and sublingual glands-and (ii) taste fibers from anterior 2/3 of tongue (except from circumvallate papillae)
    4. Communicating branch: - loins the auricular branch of vagus.
  2. At its exit from stylomastoid foramen
    At its exit from stylomastoid foramen, facial nerve gives: -
    1. Posterior auricular nerve: - It supplies muscles of pinna, occipital belly of occipitofrontalis.
    2. Digastric nerve: - Supplies posterior belly of alatees.
    3. Stylohyoid nerve: - Supplies the stylohyoid muscles.
  3. Terminal branches
    The facial nerve divides within the parotid gland into its terminal (peripheral) branches: -
    1. Temporal branch: - Innervates frontalis muscle which allows for voluntary rising of eyebrow.
    2. Zygomatic branch: - Innervates orbicularis oculi muscle and is critical for proper eye closure.
    3. Buccal nerve: - Innervates the alatees and orbicularis oris, allowing for proper mouthclosure and cheek muscle activity.
    4. Mandibular nerve: -Innervates the platysma.
    5. Cervical branch
      *Facial nerve supplies all muscles of face except levator palpebrae superioris

Site of injury of facial nerve

  1. You have read about the branches of facial nerve and their site of origin. So, you can easily make out the site of injury from the symptoms of the patient. First see the major symptoms of facial nerve palsy: -
    1. Loss of lacrimation: - Due to involvement of greater superficial petrosal nerve.
    2. Loss of stapedial reflex: - Due to involvement of nerve to stapedius.
    3. Lack of salivation: - Due to chorda tympani.
    4. Loss of taste sensation from Anterior 2/3 of tongue: - due to chorda tympani.
    5. Paralysis of muscle of facial expression: - Due to terminal (peripheral) branches.
  2. Now you can make out the site of injury :-
  3. All the 5 symptoms (ato e) are present:Injury is at or proximal to geniculate ganglion (as all the branches of facial nerve are involved).
  4. There is no loss of lacrimation (greater superficial petorsal nerve is spared) but symptoms (b) & IInjury is distal to geniculate ganglion but proximal to or at the level of second genu from where the nerve to stapedius arises.
  5. Only symptoms I to I are present (greater petrosal and nerve to stapedius are spared) Injury is distal to second genu but proximal to origin of chorda tympani, i.e., Injury is between Second genu and mid portion of vertical segment.
  6. Only I symptom is present:Injury is distal to the origin of chorda tympani, which may be at the level of stylomastoid foramen.

Upper motor neuron vs. Lower motor neuron palsy

  1. Part of facial nucleus that supplies muscles of upper part of face receives corticonuclear (cortex to nucleus) fibers from both sides of motor cortex. In contrast, the part of facial nucleus that supplies muscles of lower part of face receives corticonuclear fibers only from opposite motor cortex. Thus, if the lesion is proximal (above) the facial nucleus (upper motor neuron lesion), the upper facial muscles are partially spared because of alateess of opposite motor cortex for upper facial muscles. It the lesion is distal to facial nucleus (lower motor neuron lesion), there is involvement of all muscles of the’ face on ipsilateral side.
  2. UMN lesion causes contralateral paresis, while LMN causes ipsilateral paresis.

Vestibulocochlear (VIII) Cranial Nerve

It is a pure sensory nerve carrying special somatic afferent fibers and consists of two components (vestibular and cochlear) transmitting sensory information from membranous labyrinth to brain. Vestibular component (vestibular nerve) is concerned with equilibrium(Balanceand cochlear component (cochlear nerve) is concerned with hearing. VIII nerve lies in internal acoustic meatus along with labyrinthine vessels, and motor and sensory (nerve of Wrisberg) roots of VII nerve.


Cochlear nerve and pathway of hearing:

Cochlear nerve is formed by axons of bipolar neurons of spiral ganglion (cochlear ganglion). Cochlear nerve carries impulse from sense organ (organ of corti) to dorsal and ventral cochlear nuclei. The auditory pathway is as follows:-


Vestibular nerve and vestibular pathway

Vestibular nerve is formed by axons of bipolar neurons of scarpa’s ganglion (vestibular ganglion). The dendrites of bipolar neurons innervate the hair cells of cristae of semi-circular canals and the hair cells of maculae of utricle and saccule. The axons form vestibular nerve. Vestibular nerve ends in the vestibular nuclei. These nuclei send fibers to cerebellum, motor nuclei of brain stem (III, IV, VI and IX nerves) and anterior horn cells of spinal cord,


Glossopharyngeal (IX) Cranial Nerve

It is the nerve of third branchial (pharyngeal) arch. It is a mixed nerve. Its functional components are:-


Functional component




Special visceral (branchial) efferent

Nucleus ambiguous



General visceral efferent

Inferior salivatory

Parotid gland (via otic ganglion)

Parasympathetic secretomotor
to parotid gland.

General visceral afferent

Nucleus alatees (lower part)

Carotid sinus

Carotid body


Soft palate

Control of BP

Controls respiration

Initiates swallowing reflex

Palatal reflex

Special visceral afferent

Nucleus alatees (upper part)

Posterior 1/3 tongue and

circumvallate papillae

Taste sensation

General somatic afferent

Spinal nucleus of V

Middle ear, tympanic

mastoid antrum, auditory tube

Middle ear pain


Glossopharyngeal nerve leaves the cranial cavity through jugular foramen. It descends between IN and ICA deep to styloid process and structures attached to it. It winds round the stylopharyngeus and lying in front of it, and enters pharyngeal wall between superior and middle constrictor muscles and divides into terminal branches.



Branches of IX nerve

  1. Tympanic nerve (Jacobson’s nerve):- Carries preganglionic parasympathetic secretomotor fibers which leave the tympanic plexus via lesser petrosal nerve to relay in otic ganglion. Postganglionic fibers from ganglion supply parotid gland.
  2. Carotid branch (nerve of herring):- For carotid body and carotid sinus.
  3. Branch to stylopharyngeus
  4. Pharyngeal branches: - Form pharyngeal plexus with branches of vagus and sympathetic nerves.
  5. Tonsilarbranches: - Supply tonsil and soft palate.
  6. Lingual branches: - Supply posterior one thirdof tongue and circumvallate papillae, carrying both taste and general sensations.

Tympanic plexus

  1. Tympanic plexus is formed by:-
    1. Tympanic branch of glossopharyngeal nerve.
    2. Superior and inferior caroticotympanic nerves which are branches of sympathetic plexus around internal carotid artery.
  2. Tympanic plexus contains preganglionic secretomotor fibers which leave tympanic plexus via lesser petrosal nerve to relay in otic ganglion. Postganglionic fibers from otic ganglion supply parotid gland.
  3. Tympanic plexus also innervates mucous membrane of middle ear, alatees tube, and mastoid antrum and air cells.


Vagus (X) Nerve

Vagus nerve is the nerve of 4th and 6th pharyngeal arches. It is a mixed nerve containing approximately 80% of sensory fibers and 20% of motor fibers. It is the longest cranial nerve and named as vagus because of its extensive (‘Vague’) course through head, neck, thorax and abdomen. The fibers of cranial root of accessory nerve are distributed through branches of vagus nerve.

The vagus nerve bears two ganglia: superior ganglion lies in jugular foramen and inferior ganglion lies near base of skull.


Functional components of vagus are:-

  1. Special visceral (branchial) efferent: - Arise in nucleus ambiguous and supplies muscles of larynx, pharynx (except stylopharyngeus), and soft palate (except tensor veli alatee).
  2. General visceral efferent: - Arise in dorsal nucleus of vagus and carry preganglionic parasympathetic fibers. These are distributed to thoracic, lung and abdominal (up to right 2/3 of transverse colon) viscera.
  3. General visceral afferent: - Nucleus tractus alatees (lower part) receives sensations from pharynx, larynx, trachea, esophagus and thoracic and abdominal viscera.
  4. Special visceral afferent :- Nucleus tractus alatees (upper part) receives taste sensation from posterior most part of tongue (Valleculae) and epiglottis through internal laryngeal nerve.
  5. General somatic afferent: - Distributed to skin of auricle, external meatus, and tympanic membrane and terminate in spinal nucleus of trigeminal.


Course and relations

The nerve is attached to medulla by about ten rootlets. These rootlets unite to form main nerve which leaves cranial cavity through jugular foramen. It descends vertically downwards within the carotid sheath in the neck, first betweenin (laterally) and ICA (medially), and then betweenin and common carotid artery. Right vagus enters thorax crossing in front of 1stpart of right subclavian artery whereas left vagus descends in between left common carotid and left subclavian arteries.


Branches of vagus nerve

  • In jugular foramen, the superior ganglion gives off: (i) meningeal branch for dura of posterior cranial fossa; and (ii) Auricular branch (Arnold’s nerve or Alderman’s nerve for auricle, external meatus and tympanic membrane.
    Superior ganglion is connected to glossopharyngeal (IX) and cranial part of accessory (XII) nerves through communicating branches.
  •  Inferior ganglion gives following branches :-
  1. Pharyngeal branch: It contains fibers of cranial accessory nerve and takes part in forming pharyngeal plexus to supply muscles of pharynx (except stylopharyngeus) and soft palate (except tensor veli alatee).
  2. Carotid branch: for carotid body.
  3. Superior laryngeal nerve :-It divides into two branches :-
    1. External laryngeal nerve: - It is motor branch and supplies cricothyroid muscle. It accompanies superior thyroid artery). To avoid damage to this nerve, the superior thyroid artery is ligated close to the gland.
    2. Internal laryngeal nerve: - It is sensory branch which supplies mucous membrane of larynx above vocal folds and carries taste sensations from posterior most part of tongue (Valleculae) and epiglottis.
  4. Recurrent laryngeal nerve: - On right side it arises in the root of neck and winds around first part of right subclavian artery, It may be anterior (superficial) or posterior (deep) to inferior thyroid artery. On left side it arises in thorax (superior mediastinum) and winds around the arch of aorta immediately behind the attachment to ligamentum arteriosum. It is usually posterior (deep) to inferior thyroid artery or between its branches. Recurrent laryngeal nerve supplies all intrinsic muscles of larynx (except cricothyroid) and mucous membrane of larynx below vocal fold. It also gives branches to deep cardiac plexus, trachea, esophagus and inferior constrictor. Inferior thyroid artery is ligated away from gland to avoid injury to nerve. Left nerve is more liable to damage.
  • On both sides the recurrent laryngeal nerve.
  1. Ascends in or near tracheoesophageal groove. Each nerve is behind pretracheal fascia, and runs medial or lateral or through a thickening of fascia attached to alatee cartilage &upper tracheal ring (suspensory ligament of Berry).
  2. Closely related to medial surface of thyroid gland before it passes under the lower border of inferior constrictor.
  3. Enters larynx behind the cricothyroid joint (articulation between inferior cornu & alatee).
  1. Cardiac branches: - These are superior and inferior. Out of four cardiac branches of vagi (two on each side), the left inferior goes to superficial cardiac plexus. The other three go to deep cardiac plexus.
  2. Other branches: - Pulmonary branches, esophageal branches, gastric branches, hepatic branches, alate branches.


Accessory (XI) Nerve

  1. It is a pure motor nerve and consists of two roots, cranial and spinal.
    1. Cranial root is accessory to vagus because its fibers are distributed through branches of vagus nerve. It contains special visceral (branchial) efferent fibers which arise from lower part of nucleus ambiguous. Cranial root supplies (through branches of vagus) the muscles of soft palate (except tensor veli alatee), pharynx (except stylopharyngeus), larynx and possibly the heart.
    2. Spinal root also contains special visceral (branchial) efferent fibers which arise from the spinal nucleus in the ventral horn of C1 to C5 spinal cord segments. Its fibers supply sternocleidomastoid and trapezius.
  2. Cranial root arises from medulla and leaves the cranial cavity through jugular foramen. In jugular foramen, the cranial root unites for a short distance with spinal root and again separates from it as it passes out of the foramen. The cranial root finally fuses with vagus at its inferior ganglion and is distributed through the branches of vagus.
  3. Spinal root arises from spinal nucleus in ventral horn of C1 to C5. It ascends into the cranial cavity through foramen magnum and runs towards jugular foramen and leaves cranial cavity through this foramen where it fuses with cranial root for a short distance. It soon separates from the latter and passes out of the foramen. In the neck, nerve des ends between IJV and ICA deep to styloid process and its attached muscles. It pierces anterior border of sternocleidomastoid at the junction of upper 113 and lower 2/3 of the muscle and supplies the muscle. After supplying the muscle, it emerges from posterior border of sternocleidomastoid at the junction of upper 2/3 and lower 113 of the muscle to enter the posterior triangle of neck and finally enters trapezius muscle to supply it. Due to its superficial course nerve can be easily damaged in posterior triangle of neck by surgical incision and drainage of abscess, stab wounds in neck, and surgical removal of cancerous lymph node.

Pharyngeal plexus

The pharyngeal plexus is formed by –

  1. Pharyngeal branch of vagus carrying fibers of cranial accessory nerve: Motor supply for muscles of pharynx (except stylopharyngeus) and soft palate (except tensor alate).
  2. Pharyngeal branches of glossopharyngeal nerve for sensory supply of mucosa of pharynx (except nasopharynx above the level of opening of auditory tube).
  3. Pharyngeal branches of superior cervical sympathetic ganglion.


Hypoglossal (XII) Nerve

  1. It is a purely motor nerve. Its functional components are :-
    1. General somatic efferent: Arise from hypoglossal nucleus and innervates all intrinsic and extrinsic muscles of tongue (except palatoglossus).
    2. General somatic afferent: Proprioceptive sensations from tongue muscles reach mesencephalic nucleus of V nerve.
  2. Hypoglossal nerve arises from medulla and leave cranial cavity through hypoglossal canal (anterior condylar canal). In the neck, nerve passes forward on the superficial surface of hyoglossus. Somefibers of ventral ramus of C1 nerve join the hypoglossal nerve and are distributed through its branches.


It addition to its own fibers, the nerve also carries some fibers from C, spinal nerve.

  1. Branches of hypoglossal nerve proper: Supply all muscles of tongue except palatoglossus.
  2. Branches of hypoglossal nerve contain C, fibers: These are
    1. Meningeal branch: Supply dura mater of posterior cranial fossa.
    2. Descending branch (descending hypoglossi or upper root of ansa cervicalis): forms ansa cervicalis by communicating with inferior root of ansa cervicalis.
    3. Branch to thyrohyoid (C1)
    4. Branch to geniohyoid(C1)

Ansa cervicalis

  1. Ansa cervicalis is a thin nerve loop that lies embedded in anterior wall of carotid sheath. It is formed by a superior and an inferior root. The superior root is the continuation of descending branch of hypoglossal nerve (descendens hypoglossi) which carries fibers of C1 spinal nerve. Inferior root (descending cervical nerve) is derived from 2nd and 3rd cervical spinal nerves.
  2. Superior root supplies superior belly of omohyoid whereas ansa cervicalis supplies sternohyoid, sternothyroid, and inferior belly of omohyoid.

Note:-Thyrohyoid and geniohyoid are supplied by separate branches of C1 nerve through hypoglossal nerve (not by ansa cervical is or any of its root).

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