Trigeminal Nerve (V1 & V2)

• The Trigeminal nerve (V1 & V2) are part of the Peripheral Nervous System

Trigeminal Nerve Facts

• The trigeminal nerve:
  • Is the fifth cranial nerve
  • Is the largest cranial nerve
  • Has both Somatic (general) sensory and somatic (branchial) motor functions
  • Provides motor function to derivatives of the 1st pharyngeal arch
• The nuclei include four trigeminal nuclei: one motor,(motor nucleus of trigeminal nerve) and three sensory (mesencephalic, principal sensory and spinal nuclei of trigeminal nerve).
• The trigeminal nerve leaves the anterior aspect of the pons as a small motor root and a large sensory root.
• The large sensory root expands to form the trigeminal ganglion.
• The trigeminal ganglion is flattened and crescent-shaped, and lies within the trigeminal cave (Meckel cave) lateral to the cavernous sinus.
• The motor root of the trigeminal nerve is situated below the sensory ganglion and is completely separate.
• The ophthalmic (V1), maxillary (V2), and mandibular (V3) nerves arise from the anterior border of the ganglion and are present in the middle cranial fossa.

Ophthalmic Nerve (V1)

• The Ophthalmic Nerve (V1):
  • Is purely sensory.
  • Runs forward in the lateral wall of the cavernous sinus in the middle cranial fossa
  • Enters the orbital cavity through the superior orbital fissure
  • Divides into three branches: the lacrimal, frontal, and nasociliary nerves
• The lacrimal nerve:
  • Joins with the zygomaticotemporal branch of the maxillary nerve
  • The zygomaticotemporal branch contains parasympathetic secretomotor fibers to the lacrimal gland.
  • Then enters the lacrimal gland and gives branches to the conjunctiva and skin of the upper eyelid.
• The frontal nerve:
  • Runs forward on the upper surface of the levator palpebrae superioris muscle
  • Divides into the supraorbital and supratrochlear nerves
  • The nerves leave the orbital cavity and supply the frontal air sinus and the skin of the forehead and scalp.
• The nasociliary nerve:
  • Runs medially
  • Crossess the optic nerve
  • Runs forward on the upper border of the medial rectus muscle
  • Continues as the anterior ethmoid nerve
  • Descends at the side of the crista galli to enter the nasal cavity
  • Gives off two internal nasal branches
  • Then supplies the skin of the tip of the nose with the external nasal nerve.
• The nasociliary nerve branches include:
  • Sensory fibers to the ciliary ganglion
  • Long ciliary nerves: contains sympathetic fibers to the dilator pupillae muscle and sensory fibers to the cornea
  • Infratrochlear nerve: supplies the skin of the eyelids
  • External nasal nerve: supplies the skin of the dorsum up to the tip of the nose
  • Anterior and posterior ethmoidal nerve: provides sensory to the ethmoid and sphenoid sinuses
• Integrity examined by checking the Corneal Reflex:
  • Integrity is tested by touching the cornea, which is also supplied by CN V1, with a wisp of cotton
  • Should evoke a reflexive blink.

Maxillary Nerve (V2)

• Maxillary Nerve (V2):
  • Arises from the trigeminal ganglion in the middle cranial fossa
  • Is purely sensory in function
  • Passes forward in the lateral wall of the cavernous sinus
  • Leaves the skull through the foramen rotundum
  • Crosses the pterygopalatine fossa
  • Enters the orbit through the inferior orbital fissure.
  • Continues as the infraorbital nerve in the infraorbital groove
  • Emerges on the face through the infraorbital foramen
• It gives sensory fibers to the skin of the face and the side of the nose.
• Branches include:
  • Meningeal branches: supply the dura mater of the anterior part of the middle cranial fossa
  • Zygomatic branch: divides into the zygomaticotemporal and zygomaticofacial nerves that supply the skin of the face
    • the zygomaticotemporal branch give parasympathetic secretomotor fibers to the lacrimal gland, via the lacrimal nerve
  • Ganglionic branches: two short nerves suspend the pterygopalatine ganglion in the pterygopalatine fossa.
  • Posterior superior alveolar nerve: supplies the maxillary sinus as well as the upper molar teeth and parts of the gum and cheek
  • Middle superior alveolar nerve: supplies the maxillary sinus as well as the upper premolar teeth, gums, and cheek
  • Anterior superior alveolar nerve: supplies the maxillary sinus as well as the upper canine and incisor teeth, plus gum and cheek

Pterygopalatine Ganglion

• Pterygopalatine Ganglion:
  • Also called Sphenopalatine Ganglion
  • Is a parasympathetic ganglion
  • Is suspended from the maxillary nerve in the pterygopalatine fossa
  • Has a secretomotor function to the lacrimal and nasal glands
  • Contains sensory fibers that have passed through the ganglion from the nose, palate, and pharynx
• The Parasympathetic and Sympathetic Fibers:
  • The parasympathetic fibers to the pterygopalatine ganglion come from the facial nerve by way of its first branch, the greater petrosal nerve
  • This joins the deep petrosal nerve
  • The nerve passes through the foramen lacerum to form the nerve of the pterygoid which passes anteriorly through this canal to the pterygopalatine fossa -Parasympathetic fibers:
  • Are contained in the greater petrosal nerve
  • Synapse in the pterygopalatine ganglion
• The deep petrosal nerve:
  • Is a sympathetic nerve
  • Arises from the internal carotid plexus as the artery exits the carotid canal
• It conveys postsynaptic fibers from nerve cell bodies in the superior cervical sympathetic ganglion to the pterygopalatine ganglion by joining the nerve to the pterygoid canal.
• The fibers do not synapse in the ganglion but pass directly through it into the branches (of CN V₂).
• It runs to the lacrimal gland, the palatine glands, and the mucosal glands of the nasal cavity and superior pharynx.
• The pterygopalatine ganglion: -Has orbital branches that enter the orbit through the inferior orbital fissure -Also Has greater and lesser palatine nerves that supply the palate, the tonsil, and the nasal cavity
  • Plus A pharyngeal branch- Supplies the roof of the nasopharynx
  • And The posterior (superior & inferior) lateral nasal nerves and the nasopalatine nerve

Trigeminal Neuralgia

• Is a relatively common condition in which the patient experiences excruciating pain in the distribution of the mandibular or maxillary division, with the ophthalmic division usually escaping
• Usually is caused by pressure on the trigeminal nerve close to where it enters the brain stem(by an artery or vein).
• Microvascular decompression (MVD) surgery is regarded as the most long-lasting treatment for trigeminal neuralgia caused by blood vessel compression.

Trigeminal Sensory Branches

• The Sensory branches come from the Trigeminal Nerve to the Face
• V2 - Maxillary-to skin of cheek below orbit -
  • Comes via the Zygomaticotemporal, Zygomaticofacial, and Infraorbital
• V3- Mandibular- to skin of jaw and face below angle of mouth -
  • Comes via the Auriculotemporal, Buccal, and Mental route
• V1 - Ophthalmic - to skin above orbit -
  • Comes via the Lacrimal, Supraorbital, Supratrochlear, Infratrochlear, and External Nasal Nerve(branch of Ant. Ethmoidal N.) route

The trigeminal nerve is the fifth and largest cranial nerve. It has both somatic sensory and somatic motor functions. It provides motor function to derivatives of the 1st pharyngeal arch.