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Lacrimal nerve

The lacrimal nerve is a delicate sensory branch of the ophthalmic division of the trigeminal nerve (cranial nerve V1). It plays a vital role in providing sensory innervation to the lacrimal gland, conjunctiva, and the lateral part of the upper eyelid. Traversing through the superior orbital fissure, the lacrimal nerve is essential for tear production and ocular surface sensation. Its anatomical course and small size make it challenging to visualize on imaging modalities, but advanced MRI and CT can help assess its presence, pathology, or involvement in orbital diseases.

Synonyms

  • N. lacrimalis (Latin)

  • Branch of ophthalmic nerve (V1)

  • Sensory branch to lacrimal gland

  • Lacrimal branch of trigeminal nerve

Function

  • Provides sensory innervation to the lacrimal gland

  • Supplies sensation to the lateral aspect of the upper eyelid and conjunctiva

  • Plays a role in tear secretion via parasympathetic fibers (carried with zygomatic nerve branch from the maxillary nerve)

  • Contributes to the sensory pathway for ocular surface and periocular region

MRI Appearance

  • T1-Weighted Images:

    • The lacrimal nerve itself is generally not visualized due to its small caliber.

    • If visible, it appears as a thin, hypointense linear structure within the superior lateral orbit.

  • T2-Weighted Images:

    • Appears as a faint hypointense or isointense linear structure compared to surrounding orbital fat.

    • Surrounding inflammation, mass, or nerve enlargement may enhance visualization.

  • STIR (Short Tau Inversion Recovery):

    • Nerve pathology, such as inflammation or edema, may show hyperintense signal.

    • Normal nerve is usually not distinctly visualized unless abnormal.

CT Appearance

  • The lacrimal nerve is typically not directly visualized on standard CT due to its small size.

MRI images

Lacrimal nerve mri image