However, it is important to recognize that similar symptoms and signs can be caused by injury or compression of the sciatic nerve outside the spine, either in the buttock or thigh.
The sciatic nerve is the longest and widest nerve in the body, extending from the spine all the way to the foot, and contributes most of the nerve supply to the leg:
Sciatic nerve injury presents with:
1. Numbness affecting the entire leg, aside from the front of the thigh.
2. Weakness of the hamstrings, and all movement at the ankle.
3. Absent ankle jerk.
Sciatic Nerve Injury in the Buttock:
The nerve can be injured by misplaced buttock injections, gunshot wounds and knife injury. Buttock injections should be given in the upper outer quadrant to avoid the sciatic nerve
The sciatic nerve injury can also be injured by prolonged sitting on a toilet seat, either from direct nerve compression or hemorrhage and compartment syndrome into the gluteal muscles. This has been reported in cases of severe prolonged diarrhea, or drug induced coma on the toilet, so called toilet seat neuropathy.
Sciatic Nerve Injury at the Hip:
Sciatic nerve injury occurs in as many as 1%–3% of patients who undergo total hip replacement surgery, usually from a stretch injury to the nerves, but occasionally from a misplaced crew, broken piece of wire, fragment of bone or cement pressing on the nerve:
This presents with buttock tenderness and pain, radiate down the posterior thigh. Symptoms are made worse by prolonged sitting, bending at the waist, and activities involving hip adduction and internal rotation. The pain can be reproduced by deep palpation over the sciatic notch.
Diagnostic modalities such as CT, MRI, ultrasound, and EMG may all be normal in piriformis syndrome, but are still useful for excluding other conditions.
Magnetic resonance neurography is a specialized imaging technique which can confirm the presence of sciatic nerve irritation or injury of the sciatic nerve in the piriformis muscle.
Conservative treatment can include medications, physical therapy and stretching, or injection of a paralysing agent such as botulinum toxin into the piriformis muscle under ultrasound or CT control. Surgery may be necessary for recalcitrant cases.