M01.02.025 Opthalmic Nerve

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Learning Objective: Understand the anatomy, branches, sensory distribution, autonomic connections, and clinical significance of the ophthalmic nerve (CN V1).

Ophthalmic Nerve (CN V1)

  • First division of the trigeminal nerve (CN V).
  • Purely sensory: supplies the upper face, scalp, upper eyelid, cornea, and nasal structures.

Anatomical Course

Origin:

  • The trigeminal nerve arises from four nuclei in the brainstem:
    • Mesencephalic (sensory)
    • Principal sensory (sensory)
    • Spinal trigeminal (sensory)
    • Motor nucleus (supplies V3 only)
  • Trigeminal Ganglion:
    • Located in Meckel’s cave, lateral to the cavernous sinus.
    • From here, CN V divides into V1, V2, and V3.

Course of V1:

  • Travels lateral to the cavernous sinus.
  • Gives off recurrent tentorial branch → tentorium cerebelli.
  • Exits via the superior orbital fissure.
  • Divided into three branches:
    • Frontal nerve
    • Lacrimal nerve
    • Nasociliary nerve

Branches and Sensory Distribution

Branch Target Structures Special Notes
Frontal Supraorbital: upper eyelid, conjunctiva, scalp
Supratrochlear: forehead, upper eyelid		 Largest branch
Lacrimal Upper eyelid, conjunctiva, lacrimal gland (sensory) Receives parasympathetic fibres via the zygomatic nerve (CN V2) to the lacrimal gland
Nasociliary Long ciliary nerves: cornea, ciliary body, iris
Anterior & posterior ethmoid nerves: frontal, ethmoid, sphenoid sinuses
Infratrochlear: bridge of nose, upper eyelid		 Long ciliary nerves carry sympathetic fibres to the dilator pupillae

Cutaneous Innervation:

  • V1 supplies the forehead, upper eyelid, dorsum of the nose, and anterior scalp.
  • Borders are sharp with minimal overlap.

Autonomic Functions (Hitchhiking Fibres)

  • Sympathetic fibres: superior cervical ganglion → long ciliary nerves → dilator pupillae.
  • Parasympathetic fibres: pterygopalatine ganglion → zygomatic nerve (V2) → lacrimal nerve → lacrimal gland.

Clinical Relevance

Corneal Reflex

  • Afferent limb: CN V1 (ophthalmic nerve).
  • Efferent limb: CN VII (facial nerve) → orbicularis oculi contraction.
  • Loss of reflex → lesion of CN V1 or CN VII.

Sympathetic/Parasympathetic Lesions

  • Sympathetic: miosis, ptosis (Horner’s syndrome).
  • Parasympathetic: dry eye due to lacrimal denervation.

High-Yield Points

  • V1 = sensory only.
  • Divides into the frontal, lacrimal, and nasociliary nerves.
  • Cornea → V1 sensory, CN VII motor (corneal reflex).
  • Sympathetic & parasympathetic fibres “hitchhike” along V1 branches.

Activity:

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