Trigeminal nerve

1. Definition

The trigeminal nerve is the 5th cranial nerve and has fibres of special visceromotory and general somatosensory quality. It innervates the skin of the face and the masticatory muscles. It also carries fibres of general visceromotory quality, which innervate the glands.

2. Anatomy

2.1 Branches of the trigeminal nerve

The trigeminal nerve originates from the lateral edge of the bridge (pons) and runs to the petrous bone pyramid, where it breaks through the dura mater. Two roots can be distinguished at its origin:

• the sensory root
• the motor root

The trigeminal nerve has three major branches: the V1 (also called the ophtalmic nerve), the V2 (also called the maxillary nerve) and the V3 (the mandibular nerve). Those branches split at the trigeminal ganglion which is located in the trigeminal impression.

2.1.1 V1 – the ophthalmic nerve

Before the ophtalmic nerve exits the skull through the superior orbital fissure, it gives a meningeal branch. Then it gives the:

•  frontal nerve
  • supraorbital nerve
  • supracochlear nerve
• nasociliar nerve
  • anterior and posterior ethmoidal nerve
    • external nasal branch
  • infratrochlear nerve
  • long ciliar nerves
• lacrimal nerve
  • • ramus communicans cum nervi lacrimalis (gives visceromotory fibres for the innervation of the lacrimal gland)

2.1.2 V2 – the maxillary nerve

Before the maxillary nerve exits the skull through the foramen rotundum, it gives a meningeal branch. Then it splits up in the pterygopalatine fossa and gives the:

• infraorbital nerve
  • anterior superior alveolar rami
  • medial superior alveolar rami
• zygomatic nerve
  • zygomaticofacial nerve
  • zygomaticotemporal nerve
• posterior superior alveolar nerves
• posterior nasal nerves
• greater and lessor palatine nerves

2.1.3 V3 – the mandibular nerve

The mandibular nerve exits the skull through the foramen rotundum. It also gives a meningeal branch which enters back into the skull through the foramen spinosum (with the medial meningeal artery). The branches of the mandibular nerve carry special visceromotory fibres (for the masticatory muscles) and somatosensory fibres. These are:

• profound temporal nerve
• medial and lateral pterygoid nerve
• masseteric nerve
• nerve to tensor veli palatini
• tympanic tensor nerve
• buccal nerve
• auriculotemporal nerve (goes around the medial meningeal artery and gets general visceromotoric fibres from the ganglion oticum to innervate the parotid gland)
• lingual nerve (chorda tympani joins with general visceromotoric fibres to innovate the submandibular gland)
  • inferior alveolar nerve (through mandibular canal)
    • mental nerve
• mylohyoid nerve

2.2 Nuclei of the trigeminal nerve

The cranial nerve nuclei of the trigeminal nerve are:

Special visceromotoric nucleus: 

• Motor nucleus of trigeminal nerve

General somatosensory nuclei:

• Mesencephalic nucl. of trigeminal nerve
• Main sensory nucl. of trigeminal nerve
• Spinal nucl. of trigeminal nerve