Sciatic nerve injury

1. From what nerve roots does the sciatic nerve originate? What is the path of the nerve?
2. What muscles are innervated by the sciatic nerve?
3. Why is the sciatic nerve more susceptible to injury?
4. What sensory branches are given off directly by the sciatic nerve?
5. What are common causes of sciatic injury?
6. What are the symptoms and EMG findings in sciatic nerve injury?

Answers:
1. L4-S3. They become the posterior division of the lumbosacral plexus. It exits the pelvis through the greater sciatic foramen, between the greater trochanter and ischial tuberosity. It splits into the tibial and peroneal divisions in the mid-thigh.
2. The peroneal div innervates the short head of the biceps femoris. The tibial div innervates the long head of the biceps femoris, the semitendinosus, the semimembranosus, and the adductor magnus.
3. It is anchored at the fibular head.
4. The sural nerve.
5. Hip trauma, hip replacement, injection, hematoma, pelvic fx, penetrating wounds, pregnancy, piriformis syndrome (compression of sciatic nerve at pelvic outlet as it runs through piriformis).
6. Symptoms vary depending on which portion of the nerve is involved. NCS shows abnormal superficial peroneal and sural SNAPs, as well as tibial and peroneal CMAPs.