Sciatica is the term used to describe radiating nerve pain that begins in the low back and buttock region, runs down the back or side of the thigh and leg, and often into the foot. The term came about because the pain is in the distribution of the sciatic nerve, which is a confluence of the lower spinal nerves (L4-S3) in the buttock region.
There are a number of conditions that may cause sciatica, but the most common is a herniated disc (herniated nucleus pulposus). When an intervertebral disc is injured and protrudes into the spinal canal, it can impinge on the spinal cord and nerves and cause pain. The pain may be in the back or leg(s), or both. If the pain radiates into the leg(s), it is called sciatica. Other conditions may also cause sciatica, such as a bone spur (osteophyte) pinching a spinal nerve, or more rarely a tumor or infection. Conditions affecting the sciatic nerve in the buttock and thigh include piriformis syndrome and sacroiliac dysfunction.
Sciatica is typically present in one leg only, but occasionally in both. The leg symptoms may manifest as a shooting electricity pain down the buttock, back of the thigh and calf, and into the foot. The sciatica pain may also have a component of numbness, tingling (parasthesia), and/or weakness. Patients may have difficulty sitting or finding a comfortable position because of the pain. Leg pain that arises from arthritis of the knee or hip is not actually sciatica, since it is not resulting from compression or irritation of the sciatic nerve. This type of pain is called referred pain, when the pain of a nearby joint causes the entire region or extremity to be painful.
Patients with sciatica may have difficulty sitting, but may also have trouble standing and walking. The sciatica pain is more frequently worse with sitting, because sitting tends to aggravate discogenic injuries and disc herniations. Weakness and numbness of the leg and foot muscles may be present in patients with significant nerve compression.
An MRI of the spine is most useful to evaluate a patient with sciatica. An MRI utilizes a powerful magnet and computer system to generate images in three dimensions of all structures, including the intervertebral disc, spinal cord and nerves, muscles, bone, and other soft tissues. Regular x-rays are most useful to evaluate fractures, instability, or arthritis changes of the spine. However, x-rays do not allow one to visualize the soft tissues of the spine such as disc, nerves, or muscles, and usually will not identify the cause of sciatica symptoms.
There are no laboratory tests used to diagnose a herniated disc. Occasionally, specific tests are ordered to rule out infection or other causes or back pain and/or sciatica.
Electromyography and nerve conduction velocity (EMG/NCV) tests are useful to determine which nerve is affected, and how severely it is damaged or irritated. The test will often clarify where a nerve is actually being compressed – whether it is in the back, buttock, or leg.
The diagnosis of sciatica is typically made by taking a detailed patient history alone. However, an MRI of the lumbar spine will often be required to confirm the actual cause of the sciatica pain. It is important for the clinician to conduct a thorough history and clinical examination prior to formulating the final diagnosis so as not to misdiagnose this condition.
Fortunately, sciatica is a condition that frequently will improve on its own over the course of days or weeks. Specific treatments for sciatica vary, depending on the condition causing the sciatic nerve compression or irritation. The majority of cases of sciatica are caused by a herniated disc or bone spur pinching a spinal nerve in the lower spine. Conservative treatments include a short period of rest or activity reduction, as well as non-steroidal anti-inflammatory medications. Pain medicines and/or narcotics may also be prescribed for severe pain and spasm. Epidural steroid injections and/or nerve root blocks may also be utilized for severe pain or moderate pain that is no longer responding to other conservative measures. Surgical decompression, such as microscopic lumbar discectomy (MLD) or laminectomy, may be recommended for patients who fail conservative treatments, and demonstrates a high rate of success in relieving pain and restoring function.
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