Piriformis nerve

The piriformis nerve, also known as the nerve to piriformis, is the peripheral nerve that provides motor innervation to the piriformis muscle.

Origin
The nerve to piriformis is a branch of the sacral plexus. It (typically ) arises from the posterior divisions /branches of anterior rami of S1 and S2.

Course
It enters the anterior surface of the piriformis muscle.

Variation
Origin

It may sometimes arise from the anterior ramus of S2 only.

Number

It may be doubled. An additional branch may arise from the superior gluteal nerve.

Distribution
The piriformis nerve innervates the piriformis muscle.