THE TRIGEMINAL NERVE (CN V)

 

The Origin(s)

The trigeminal nerve has four main nuclei:

  • Spinal nucleus- medulla oblongata

  • Chief or principal nucleus - pons

  • Mesencephalic nucleus - midbrain

  • Motor nucleus - pons .

  • Leaves the brain stem through the middle cerebellar peduncle in a ventrolateral location.

  • Within 1 to 2 cm of the brain stem the trigeminal nerve swells to form the very large trigeminal ganglion

  • This ganglion lies in a depression in the floor of the middle cranial fossa, lateral to the cavernous venous sinus.


  • As the fibres exit the CN V ganglion, they form three primary divisions:
  1. Ophthalmic
  2. Maxillary
  3. Mandibular

 

Division
Course
Branches
Distribution
V1
Ophthalmic division    
  • Enters the lateral wall of the cavernous sinus

  • Runs forward below the trochlear and oculomotor nerves.

  • Enters the orbit through the superior orbital fissure
Nasociliary nerve
  • External surface of the nose,
  • Anterior nasal cavity
  • Ethmoid sinuses
  • Sphenoidal sinus
  • Medial eyelids
  • Eyeball- cornea

lacrimal nerve
  • Lateral part of the upper eyelids,
  • Conjuctiva
  • Lacrimal gland.
  • Cranial dura

frontal nerve
  • Frontal sinuses,
  • Upper eyelid
  • Bridge of the nose,
  • Forehead.


V 2

Maxillary division

  • Leaves the trigeminal ganglion and enters the cavernous sinus

  • Exits through foramen rotundum

  • Enters inferior orbital fissure as the infraorbital nerve.

  • Exits through infra-orbital foramen

   
zygomatic nerve
  • Area over the zygomatic arch
  • Lateral forehead,
  • Anterior temporal area.

   
pterygopalatine nerve
  • Posterior nasal cavity
  • Nasal septum,
  • Palate

Infraorbital nerve ,
  • Upper lip and to the
  • Medial cheek
  • Lateral nose
  • Maxillary air sinus

Superior alveolar nerves
  • Maxillary teeth
  • Maxillary air sinus

V3

Mandibular division

  • Leaves the cranial vault through foramen ovale

  • Lies anteromedial to the TMJ and close to the origin of the pterygoid muscles as well as the tensor and levator veli palatini muscles.
Nervous spinosum
  • Cranial dura

auriculotemporal
  • Side of the head and scalp;
  • Anterior wall of the external auditory meatus,
  • External surface of the tympanic membrane.

Lingual nerve
  • Anterior two thirds of the tongue.

Inferior alveolar
  • teeth of the lower jaw.

Buccal nerve
  • mucosa of the mouth.

Mylohyoid nerve
  • Arises from the inferior alveolar nerve,
  • myohyoid muscle
  • Anterior belly of the digastric muscle.

Muscular branches
  • Muscles of mastication
   

 

 

 

Summary of distribution

  • Face
  • Eyelids
  • Eyes
  • Nose
  • Paranasal sinuses
  • Ear
  • Mandibular
  • Maxillary teeth
  • Gums
  • Cranial dura
  • Muscles of mastication
  • Tensor tympani
  • Tensor veli palatini

Functional Components

a) Branchiomotor to muscles of mastication (SVE)

b) Somatosensory (GSA)


Clinical disorders of the CN V

•  Paralysis or paresis of muscles of mastication is readily detectable by palpation after the patient clenches the jaw. If the involvement is peripheral, the jaw will deviate towards the side of the lesion.

(+) There is also sensory loss to the area of the face supplied by the mandibular division .

(+) The loss in bite strength will be unilateral; the muscles will be flaccid, and the muscle mass will atrophy with time. If it is an upper motor neuron lesion, the jaw reflex will be exaggerated.

(+) A bilateral weakness may be apparent even with unilateral lesion, because the corticobulbar projections are a combination of crossed and uncrossed fibres.

•  Trigeminal Neuralgia :

(+) This is one of the most common clinical problems of the trigeminal nerve.

(+) It is characterized by periods of severe shooting pain in the area of supply of the trigeminal nerve.

(+) The pain localizes to the side of the face, and involves the areas of innervation of one or more of the divisions of CN V - usually the maxillary or mandibular divisions.

(+) The origin of the pain is unknown. In severe cases however, severing of the spinal tract of the trigeminal nerve in the lower medulla below the level of the inferior olivary nucleus, offers relief.

(+) In localizing injury to branches of the trigeminal nerve, the integrity, or the lack thereof, of the autonomic innervation to salivary glands and lacrimal glands is valuable information.

If damage occurs peripheral to the hitchhikers joining the nerve, an autonomic loss accompanies the sensory loss.

•  Herpes Zoster :

(+) As with other sensory ganglia, the trigeminal ganglion is vulnerable to this infection.

(+) This viral infection results in considerable pain and ulceration of the skin and mucous membranes supplied by the affected fibres. The ophthalmic division is most frequently affected.

(+)There are a wide host of causes and effects of injury to the individual branches of the three divisions of CN V, which you will meet in your gross anatomy studies of the neck.