infratrochlear

Infratrochlear is an anatomical term used for structures located beneath the trochlea of the superior oblique muscle near the medial canthus of the eye. It most often refers to the infratrochlear nerve and the infratrochlear artery, both situated along the medial wall of the orbit and contributing to the sensory and vascular supply of the medial canthal region.

The infratrochlear nerve is a small sensory branch of the nasociliary nerve, which derives from the ophthalmic division (V1) of the trigeminal nerve. It arises within the orbit, runs medially along the orbital wall below the trochlea of the superior oblique, and exits near the medial angle of the eye. Its distribution includes the skin of the medial canthus, the lacrimal caruncle, and adjacent portions of the upper and lower eyelids, as well as some conjunctival fibers. It typically travels with accompanying vessels in the region.

The infratrochlear artery accompanies the nerve and is a small vessel derived from the ophthalmic artery. It supplies the medial canthus, portions of the eyelids, and the lacrimal sac area, with connections to other orbital and facial arteries to ensure collateral circulation in the region.

Clinical relevance includes infratrochlear nerve blocks, used to anesthetize the medial canthus and neighboring eyelid areas during procedures such as eyelid or nasal surgeries. Injury or entrapment of this nerve is uncommon but can contribute to facial pain in the medial canthal region.