What is Sciatic Nerve Block?

The longest nerve in the body, the sciatic nerve is one of the most affected by common conditions. While often thought to be a condition, sciatica is actually a symptom and is representative of pain that radiates along the sciatic nerve. The sciatic nerve provides motor and sensory innervations to the posterior aspect of the thigh extending through the entire lower extremity, except for the medial leg, which is supplied by the saphenous nerve.

  • Herniated or Bulging Disc – Most common cause of sciatica. The discs that separate the vertebra are filled with a gel-like fluid that softens the impact caused by normal, day-to-day activities that the spinal column takes the brunt of. Since the discs are designed to be soft and provide support, they have a tendency to herniate backwards through the outer disc segment and nearby ligaments.
  • Spinal Stenosis – This is a disorder that can cause a crowding of the nerves or spinal cord.
  • Piriformis syndrome – The piriformis is a large muscle that is part of the pelvis. Due to the size and placement of this muscle, should it become swollen due to overuse, stress or inflammation, it can essentially “trap” the sciatic nerve, which then causes pain (Hopavian).
  • Facet Hypertrophy – The facet joints allow for flexion and extension movements of the spine. When the facet joints become arthritic they can hypertrophy causing nerve compression.
  • Tarlov cysts – Abnormal sac of cerebrospinal fluid (Prashad).
  • Nerve sheath tumor

Procedural Description

This minimally invasive procedure involves injecting a steroid adjacent to the peripheral nerve; as opposed to an epidural steroid injection where the nerve root is targeted.

Because of the size and magnitude of the sciatic nerve, it can be effectively anesthetized from several different locations along the lower pathway. The most commonly used approach is Labatts’s, targeting the nerve in the posterior gluteal region (Bucholz) with the patient in the prone position. A local anesthetic such as lidocaine will be used as it will aid to cease the spasming cycle and the transmission of signals of pain to the brain (Boswell 2007).  The medicine then spreads along the nerve sheath and surrounding areas, reducing irritation. The entire procedure usually takes less than 15 minutes.

Risks

The associated risks of the nerve block, although rare, include:

-          Nerve damage

-          Bleeding

-          Infection

Numbness from the anesthetic may last about an hour.  A dull aching pain may occur at the injection site.  Occasionally following the procedure there may be increased irritation of the nerve causing increased pain.  This pain is typically transient and resolves within a few hours.

References

Hopayian K, Song F, Riera R, Sambandan S.The clinical features of the piriformis syndrome: a systematic review. Eur Spine J. 2010 Jul 3.

Boswell et. All.  Interventional Techniques: Evidence-based Practice Guidelines in the Management of Chronic Spinal Pain. Pain Physician 2007; 10:7-11

Bhagwat Prashad, Anil K Jain, Ish K Dhammi Tarlov cyst: Case report and review of literature Indian Journal of Orthopedics.  2007.  41:4. p401-403.

Jeffrey T. Bucholz, D.O., Eugene O. Mitchell, M.D Successful Long Term Treatment of Pediatric Cancer Pain with Peripheral Regional Anesthesia American Society of Anesthesiologists. 2004