Musculus caninus
The caninus is a facial muscle that helps move the nostril. It originates on the maxilla just below the infraorbital foramen and inserts into the lateral border of the nostril, with lower fibres blending into the orbicularis oris. Its main action is to draw back the caudal wing of the nostril. In horses it contributes to movement of the nostril. It is innervated by the dorsal buccal branch of the facial nerve (CN VII). Because it lies superficially, it can be affected by facial-nerve trauma or local soft-tissue injury, though isolated problems are uncommon.
Origin: Maxilla, ventral to the infraorbital foramen
Insertion: Lateral border of the nostril; lower fibres blend with orbicularis oris
Action: Draws back the caudal wing of the nostril
Innervation: Dorsal buccal branch of facial nerve (CN VII)
Rarely a primary clinical concern. Facial-nerve paralysis can reduce its function along with other lip muscles, leading to drooping of the lip or reduced ability to prehend food on one side. Trauma or abscesses in the facial region may involve it secondarily.
## Overview Infraorbital nerve block is a regional anesthetic used for dental procedures on the upper incisors and canine teeth. Because the nerve supplies the upper lip, the block temporarily causes
Noticeable drooping of one side of the upper lip or difficulty picking up feed on one side may indicate facial-nerve involvement; have a veterinarian examine the head. Most isolated muscle issues resolve with time if the nerve is intact.
## Overview Infraorbital nerve block is a regional anesthetic used for dental procedures on the upper incisors and canine teeth. Because the nerve supplies the upper lip, the block temporarily causes lip droop and mild difficulty eating on that side. The effect resolves as the local anesthetic wears off, usually within a few hours. ## Causes Intentional local anesthesia for dentistry. ## Diagnosis History of recent dental nerve block and transient lip asymmetry. ## Treatment None required. The effect is temporary. Soft feed may be easier until sensation returns. ## Recovery and Prognosis Excellent. Full function returns within hours. ## Prevention Not applicable (expected effect of the block). Signs include: temporary lip droop after dental work; mild difficulty eating for a few hours; asymmetric lip position that resolves
Rarely a primary clinical concern. Facial-nerve paralysis can reduce its function along with other lip muscles, leading to drooping of the lip or reduced ability to prehend food on one side. Trauma or abscesses in the facial region may involve it secondarily.
Noticeable drooping of one side of the upper lip or difficulty picking up feed on one side may indicate facial-nerve involvement; have a veterinarian examine the head. Most isolated muscle issues resolve with time if the nerve is intact.
See the Caninus on our interactive 3D horse model. Open 3D Model