Accessory Nerve Affects

Introduction to the Equine Accessory Nerve

You normally think of the cranial nerves as belonging to the head but the Accessory Nerve is a major driver of the shoulder.

Most people have never heard of it but horses show it everywhere.

CN XI — the accessory nerve — runs the trapezius. All of it. When it’s compromised, the dorsal neck loses its muscular support, the ventral chain wins by default, and the horse starts inverting. You see it as a ewe neck, a dropped topline, a shoulder that stops swinging, a neck that resists lateral flexion. It gets labeled a conformation problem and treated accordingly. It’s not. It’s typically a nerve problem.

If you’ve been working on necks that won’t release, scapular asymmetry that keeps coming back, or ewe neck that never fully resolves — this can be why.