Sciatica and the Sciatic Nerve

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Sciatica commonly describes the symptoms of pain and possibly numbness or weakness that radiate along the sciatic nerve and tend to be felt in the rear, down the back of the leg and possibly to the foot. Sciatica is one of the most common forms of pain caused by compression of the spinal nerves in the lower back, and the leg pain is usually much worse than the back pain.

The sciatic nerve is the largest single nerve in the human body; it runs from each side of the lower spine through deep in the rear and back of the thigh and all the way down to the foot, connecting the spinal cord with the leg and foot muscles.

The sciatica symptoms one feels (nerve pain, numbness, tingling, weakness) tend to be different depending on where the pressure on the nerve occurs. The patient’s pain and specific sciatica symptoms can usually be traced to where the injured/irritated nerve originates in the lower back. Typical symptoms include:

• Sciatica from L4 nerve root
  Symptoms of sciatica stemming from this level of the lower back may include: pain and/or numbness to the medial lower leg and foot; weakness may include the inability to bring the foot upwards (heel walk). The patient may have reduced knee-jerk reflex.
• Sciatica from L5 nerve root
  The patient may have weakness in extension of the big toe and potentially in the ankle (called foot drop). Symptoms of sciatica originating at this level of the lower back may include: pain and/or numbness at the top of the foot, particularly in the web between the great toe (big toe) and the second toe.
• Sciatica from S1 nerve root
  Symptoms of sciatica originating at this level of the spine may include: pain and/or numbness to the lateral or outer foot; weakness that results in difficulty raising the heel off the ground or walking on the tiptoes. The patient may have reduced ankle-jerk reflex.

• Pressure on the sacral nerve roots from sacroiliac joint dysfunction
  Symptoms may include: a sciatica-like pain or numbness that is often described as a deep ache felt inside the leg more so than a linear, well-defined geographic area of pain/numbness found in true sciatica.
• Pressure on the sciatic nerve from piriformis muscle
  

  This pressure on the sciatic nerve can tighten and irritate the sciatic nerve (called piriformis syndrome). Symptoms of piriformis syndrome may include: a sciatica-like pain and/or numbness in the leg that is usually more intense above the knee, usually starts in the rear rather than the low back, and often spares the low back of symptoms or signs.

  Piriformis syndrome can mimic the signs and symptoms of sciatica pain from a disc herniation and is part of the different diagnosis of possible causes of sciatica.

A variety of lower back problems can lead to pain that radiates along the sciatic nerve. Most often, sciatica pain is caused when the L5 or S1 nerve root in the lower spine is irritated by a herniated disc. When this happens, pain radiates into the rear and back of the thigh and calf, and occasionally may extend down to the foot. Numbness, tingling, and/or a burning or prickling sensation are also common sciatica symptoms.

Degenerative disc disease may also irritate the nerve root and cause sciatica, while conditions that mimic sciatica include piriformis syndrome and sacroiliac joint dysfunction. Sciatica may also be felt if the nerve is actually mechanically compressed, such as from spondylolisthesis, spinal stenosis, or arthritis in the spine.

• Article written by:
• Steven G. Yeomans, DC

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