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C h e c k o u t A B M P 's l a t e s t n e w s a n d b l o g p o s t s . Av a i l a b l e a t w w w. a b m p . c o m . 99 of the suprapiriformis foramen. The superior gluteal nerve is primarily a motor nerve that supplies the gluteus medius and gluteus minimus muscles. When the piriformis is hypertonic, it can trap the superior gluteal nerve against the underside of the greater sciatic notch. Next, we'll take a look at the infrapiriformis foramen and the four nerves that can be compressed by the piriformis there: sciatic, inferior gluteal, posterior femoral cutaneous, and pudendal. These nerves pass through the infrapiriformis foramen and are susceptible to compression between the piriformis muscle and the sacrospinous ligament. If there's one nerve in the body that most people are familiar with, it's the sciatic nerve. It is the largest in diameter and the longest nerve in the body. The sciatic nerve is composed of two divisions: the peroneal (or fibular) division and the tibial division. These divisions eventually split when the nerve passes around the posterior aspect of the knee. However, in some people, they also split in the piriformis region, and this can play a part in nerve compression. There are six anatomical variations that may occur between the sciatic nerve and the piriformis muscle. 3 Image 3 (page 101) shows these different variations. 1. Normal Pathway of the Sciatic Nerve The two divisions of the sciatic nerve remain together and pass inferior to the piriformis muscle. Both divisions course through the infrapiriformis foramen. 2. Peroneal Division Through the Piriformis, Tibial Division Below In this variation, the peroneal division passes directly through the middle of the piriformis muscle, while the tibial division is in the normal position. Nerve compression can be increased on the peroneal division by tendinous bands running through the muscle in addition to muscular fibers compressing the nerve. 3. Peroneal Division Above, Tibial Division Below Here, the peroneal and tibial divisions are quite separated. The peroneal division courses through the suprapiriformis foramen above the muscle with the superior gluteal nerve, while the tibial division is in the normal position below the piriformis. 4. Both Divisions Through the Middle of the Muscle Here, both divisions course directly through the middle of the muscle. As with variation #2, tendinous bands within the piriformis muscle can further aggravate the nerve beyond the compression of the nerve fibers by the surrounding muscle. 5. Peroneal Division Above, Tibial Division Through the Muscle In this variation, the tibial division courses through the middle of the muscle, while the peroneal division passes through the suprapiriformis foramen. 6. Both Divisions Above the Muscle The final variation is one in which both nerve divisions are above the piriformis and course through the suprapiriformis foramen. With both divisions of the muscle in the suprapiriformis foramen, there is less space for the superior gluteal nerve as well. While sciatic nerve compression by the piriformis gets the most attention, the other nerves in this region shouldn't be ignored. Running right next to the piriformis is the posterior femoral cutaneous nerve. As its name suggests, it is primarily a sensory nerve supplying the posterior aspect of the thigh. Sometimes, clients report posterior thigh neurological pain that only extends to the knee and not below it. In this case, it is likely that the posterior femoral cutaneous nerve is being compressed. The inferior gluteal nerve is a motor nerve that supplies the gluteus maximus. Because it is a motor nerve, compression of this nerve doesn't cause as much pain, but instead weakness or atrophy. The last nerve susceptible to compression in this region is the pudendal nerve. It is rarely discussed in the literature about piriformis syndrome and is least often involved. However, it should not be ignored because nerve compression symptoms from this muscle could easily be ascribed to some other cause. The pudendal nerve is a mixed motor and sensory nerve. It innervates many of the pelvic floor muscles and supplies sensation to the perineal region, genitalia, and anus. Pudendal nerve compression also occurs from external factors such as very hard bicycle seats that can affect competitive cyclists who are racing for long periods. Sciatic Superior gluteal Inferior gluteal Posterior femoral cutaneous Pudendal Nerves in this region and their relation to other anatomical structures. Image is from 3D4Medical's Essential Anatomy 5 application. 2