Is Sciatica a Spinal Disorder or a Symptom of a Spinal Disorder?

The term sciatica is commonly used to describe pain traveling in the distribution of the sciatic nerve - so it’s more accurate to say that it’s a symptom of a spinal disorder (not a spinal disorder itself).  The sciatic nerve is the largest nerve in the human body, about the diameter of a finger.  Before jumping into the symptoms associated with sciatica, it’s helpful to have an idea of where the sciatic nerve is and what it does.

Sciatic nerve fibers begin at the 4th and 5th lumbar vertebra (L4, L5) and the first few segments of the sacrum. The nerve passes through the sciatic foramen just below the piriformis muscle (rotates the thigh laterally), to the back of the extension of the hip and to the lower part of the gluteus maximus (muscle in the buttock, helps with thigh extension).

The sciatic nerve then runs vertically downward into the back of the thigh, behind the knee and branches into the hamstring muscles (calf) and further downward to the feet.

Sciatica Symptoms

Sciatica symptoms usually affect one side of the body.

The pain from sciatic nerve compression may be dull, sharp, burning, or accompanied by intermittent shocks of shooting pain beginning in the buttock traveling downward into the back or side of the thigh and/or leg. Sciatica then extends below the knee and may be felt in the feet.

Sometimes symptoms of sciatic nerve compression include tingling and numbness.

Sitting and trying to stand up may be painful and difficult. Coughing and sneezing can intensify the pain.

Substance P and calcitonin gene-related peptide expression in dorsal root ganglia in sciatic nerve injury rats

Several methods have been utilized to repair peripheral nerve injury,  but results have not been favorable. Thus, it is important to understand the mechanism of peripheral nerve injury.  Neuropeptides are a recently discovered neurotransmitter,  with a wide range of bioac-tivities.  A large number of clinical and experimental observations have demonstrated that peripheral nerves participate in the repair of nerve injury by secreting various neuropeptides from peripheral nerve endings.  In particular,  increasing attention has been paid to neu-  ropeptide substance P and calcitonin gene-  related peptide.

Substance P and calcitonin gene-related peptide are the main neuropeptides in peripheral nerve ganglia.  They can transmit nociception and function as excitatory transmitters in primary sensory neurons.

Furthermore,  they anterogradely transmit nociceptive information to the central nervous system and are retrogradely released in local tissues, leading to hyperalgesia.

Research Highlights
(1) Substance P and calcitonin gene-related peptide expression in dorsal root ganglia were altered
over time in rats with sciatic nerve injury.
(2)  Results showed that the expression of the neuropeptides,  substance P and calcitonin
gene-related peptide, mainly increased in the early stages after sciatic nerve injury. These neuro-
peptides may possibly serve as an index for evaluating early peripheral nerve injury.
(3) Substance P and calcitonin gene-related peptide are involved in transmitting pain signals and
play a role in repair following sciatic nerve injury.
Abstract 
The neuropeptides, substance P and calcitonin gene-related peptide, have been shown to be involved
in pain transmission and repair of sciatic nerve injury. A model of sciatic nerve defect was prepared by
dissecting the sciatic nerve at the middle, left femur in female Sprague Dawley rats. The two ends of
the nerve were encased in a silica gel tube. L 5 dorsal root ganglia were harvested 7, 14 and 28 days
post sciatic nerve injury for immunohistochemical staining. Results showed that substance P and cal-
citonin gene-related peptide expression increased significantly in dorsal root ganglion of rats with sci-
atic nerve injury. This increase peaked at 7 days, declined at 14 days, and reduced to normal levels by
28 days post injury. The findings indicate that the neuropeptides, substance P and calcitonin gene-
related peptide, mainly increased in the early stages after sciatic nerve injury.
Key Words
neural regeneration;  peripheral nerve injury;  sciatic nerve;  dorsal root ganglion;  spinal cord; 
neuropeptides;  calcitonin gene-related peptide;  substance P;  pain;  neuroprotection;  grants-
supported paper; neuroregeneration

Changma Fu, Zongsheng Yin, Defu Yu, Zuhua Yang
Department of Orthopedics, First Hospital of Anhui Medical University, Hefei 230022, Anhui Province, China
Third Clinical College, Anhui Medical University, Hefei 230022, Anhui Province, China