Cranial Nerve Series: Trigeminal Nerve (CN V)

Overview

• Cranial nerves: 12 pairs exiting brain and brainstem.
• Focus: Trigeminal nerve (CN V), which is the 5th cranial nerve.
• Functions: Sensory innervation of the face and motor control of mastication muscles.
• Divisions: Ophthalmic (V1), Maxillary (V2), Mandibular (V3).

Trigeminal Pathway

• Sensory Nuclei: Mesencephalic, Principal, Spinal nuclei.
• Motor Nucleus: Located within the brainstem.
• Trigeminal Ganglion: Where sensory routes converge before splitting into three divisions.

Divisions of the Trigeminal Nerve

Ophthalmic Nerve (V1)

• Path: Passes through the superior orbital fissure.
• Branches: NFL (Nasociliary, Frontal, Lacrimal) nerves.
  • Frontal Nerve: Bifurcates into Supraorbital and Supratrochlear nerves.
  • Nasociliary Nerve: Splits into branches like posterior and anterior ethmoidal nerves, long and short ciliary nerves, and infratrochlear nerve.
  • Lacrimal Nerve: Innervates lacrimal gland and upper eyelid.
• Function: Sensory innervation to the forehead, eyes, nasal cavity, scalp, and dura mater.

Maxillary Nerve (V2)

• Path: Passes through the foramen rotundum.
• Branches: Posterior superior alveolar, Infraorbital, Zygomatic nerves.
  • Infraorbital Nerve: Gives off anterior and middle superior alveolar branches, then exits infraorbital foramen.
  • Zygomatic Nerve: Splits into zygomatico-temporal and zygomatico-facial nerves.
• Pterygopalatine Ganglion Branches: Pharyngeal, Nasopalatine, Greater and Lesser palatine nerves.
• Function: Sensory information from the midface (lower eyelid to upper teeth and lips).

Mandibular Nerve (V3)

• Path: Passes through the foramen ovale.
• Branches: Auriculotemporal, Lingual, Inferior Alveolar, Bucal nerves.
  • Auriculotemporal Nerve: Encircles middle meningeal artery; innervates ear and temporal region.
  • Lingual Nerve: Sensory to anterior 2/3 of the tongue.
  • Inferior Alveolar Nerve: Supplies mandibular teeth, continues as Mental Nerve.
  • Buccal Nerve: Innervates cheeks and buccal mucosa.
• Motor Branches: Innervate muscles of mastication, mylohyoid, anterior belly of digastric, tensor tympani, and tensor veli palatini.
• Function: Sensory and motor innervation to lower face, jaw, and muscles of mastication.

Clinical Correlations

• Herpes Simplex Type 1: Virus can establish latent infection in trigeminal ganglia, causing recurrent infections.

Summary

• Trigeminal Nerve: Large nerve but comprehensible when broken down into its branches.
• Next Topic: Sixth cranial nerve, the abducent nerve.

Additional Information

• Purpose: Focus on both sensory and motor aspects of the trigeminal nerve.
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