Infratrochlear nerve: sensation of the inner corner of the eye
Quick facts
- Origin
- Terminal branch of the nasociliary nerve, which is a branch of the ophthalmic nerve (V1) of the trigeminal.
- Function
- Sensory: skin and conjunctiva of the medial corner of the eye, nasal root and lacrimal sac.
- Exit
- Passes below the trochlea and emerges next to the medial canthus, above the medial canthal tendon.
- Clinical relationship
- Anastomoses with the supratrochlear and infraorbital nerves, which explains overlapping areas of numbness.
The infratrochlear nerve is a small sensory branch that supplies the skin and conjunctiva of the inner corner of the eye, the side of the nasal root and the lacrimal sac. It arises from the nasociliary nerve, which is itself a branch of the ophthalmic nerve (V1), the upper division of the trigeminal nerve.
Where does it run?
Inside the orbit, the nasociliary nerve runs along the medial wall and splits into terminal branches. One of them, the infratrochlear, continues below the trochlea (the pulley of the superior oblique muscle) and leaves the orbit near the medial canthus, above the medial canthal tendon. From there it spreads to the medial upper and lower eyelids, the side of the nasal root and the area of the lacrimal sac.
Because it is a thin nerve, it can be neither seen nor palpated. What the professional observes is the clinical result: the sensation of this small area of the face.
| Structure | Role |
|---|---|
| Nasociliary | Parent trunk, branch of V1 |
| Infratrochlear | Sensory branch of the medial canthus and nasal root |
| Supratrochlear | Neighbor, supplies the medial forehead and upper eyelid |
| Infraorbital | Branch of V2, covers the lower eyelid and the side of the nose |
Why does such a small nerve matter in facial harmonization?
The medial canthus region brings together three topics that come up in practice: the nasal root, the tear trough and the medial part of the glabella. These are delicate areas, with large-caliber vessels and little margin. The infratrochlear nerve enters the picture for three practical reasons:
- Local anesthesia: infiltrations and blocks at the nasal root and medial canthus can reach the infratrochlear and supratrochlear nerves, and numbness in this area is expected and temporary.
- Differential diagnosis: pain, tingling or numbness in the inner corner of the eye and the side of the nose can have a neural, vascular or inflammatory origin. If the problem is persistent or comes with a visual change, the right move is to refer, not to explain it away as a "normal effect".
- Warning signs: the V1 territory is also where a vascular event tends to show up with pain and a color change. See vascular occlusion.
How does it relate to planning?
The infratrochlear nerve is not the target of any filler or toxin technique. It is part of the mental map of anyone assessing the transition between nose, eye and forehead. Knowing the innervation helps explain to the patient why the skin of the inner corner of the eye may feel "asleep" after anesthesia, and helps record sensory complaints correctly in the patient record.
Also called: infratrochlear branch of the nasociliary, nervus infratrochlearis.
Frequently asked questions
Is the infratrochlear nerve motor or sensory?
It is purely sensory. It carries the sensation of touch, pain and temperature from the inner corner of the eye and the nasal root to the trigeminal nerve.