Sciatic Nerve Neurodynamics Assessment
Sciatic Nerve (L4 – S3)
This is the largest nerve in the body, and innervates the muscles of the posterior thigh and all muscles of the leg and foot. The sciatic trunk tibial component and a common peroneal component which innervate five muscles before dividing to form the tibial and common peroneal nerves.
Common Peroneal Division (dorsal divisions L4—L5 and S1—S2)
Tibial Division (ventral divisions L4 – L5 and S1 – S3)
Clinical Pathology
A great deal of variability exists in relationship of the sciatic nerve to the piriformis muscle and short external rotators. In approximately 85% of cases the sciatic nerve exits the pelvis deep to the muscle belly of the piriformis. It is usually superficial (posterior to the other external rotators). In 11% of individuals a portion of the piriformis muscle splits the common peroneal nerve and tibial nerve. These anatomic variations are important in the interpretation of intra-operative findings.
Different types of sciatica pain:
Sciatica from L4 nerve root (usually the L3-L4 level)
The patient may have reduced knee-jerk reflex. 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).
Sciatica from L5 nerve root (usually the L4-L5 level)
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 to the top of the foot, particularly in the web between the great toe (big toe) and the second toe.
Sciatica from S1 nerve root (the L5-S1 level)
The patient may have reduced ankle-jerk reflex. 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.
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, 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 the 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, usually more intense above the knee, which usually starts in the rear rather than the low back, often sparing 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 differential diagnosis of possible causes of sciatica
Straight-Leg Raising (SLR)
The Straight-Leg Raising test can detect abnormal neurodynamics
Tests the mobility of the dura matter from the forth lumbar level downwards. It also tests the mobility of the fourth and fifth lumbar nerve roots, and the intraspinal extent of the first and second sacral nerve roots.
It remains a valid test only so long as the dura matter and its investment of the nerve roots retain sensitivity.
Tension through the structure on the L5 and/or S1 nerve root. The SLR my produce leg pain by stretching the nerve root