Sciatic Nerve

Nerve: Sciatic nerve
Left gluteal region, showing surface markings for arteries and sciatic nerve.
Latin	nervus ischiadicus
Gray's	subject #213 960
Innervates	Quadratus femoris Obturator internus Gemelli Quadratus femoris Glutæus maximus Adductor magnus Biceps femoris Semitendinosus Semimembranosus Adductor magnus
From	lumbar plexus and sacral plexus: L4-S3
Dorlands/Elsevier	n_05/12566006

The sciatic nerve is a large nerve that runs down the lower limb. It is the longest single nerve in the body.

The Sciatic supplies nearly the whole of the skin of the leg, the muscles of the back of the thigh, and those of the leg and foot.

Contents [hide] 1 Anatomical Course 2 Branches 3 Trivia 4 Pathology 5 Additional images 6 External links

[edit] Anatomical Course

The nerve enters the lower limb by exiting the pelvis through the greater sciatic foramen, below the Piriformis muscle.

It descends between the greater trochanter of the femur and the tuberosity of the ischium, and along the back of the thigh to about its lower third, where it divides into two large branches, the tibial and common peroneal nerves.

This division may take place at any point between the sacral plexus and the lower third of the thigh.

When it occurs at the plexus, the common peroneal nerve usually pierces the Piriformis muscles.

In the upper part of its course, the nerve rests upon the posterior surface of the ischium, the nerve to the Quadratus femoris, the Obturator internus and Gemelli; it is accompanied by the posterior femoral cutaneous nerve and the inferior gluteal artery, and is covered by the Gluteus maximus.

Lower down, it lies upon the Adductor magnus, and is crossed obliquely by the long head of the Biceps femoris.

[edit] Branches

The nerve gives off articular and muscular branches.

• The articular branches (rami articulares) arise from the upper part of the nerve and supply the hip-joint, perforating the posterior part of its capsule; they are sometimes derived from the sacral plexus.

• The muscular branches (rami musculares) are distributed to the following muscles of the lower limb: Biceps femoris, Semitendinosus, Semimembranosus, and Adductor magnus. The nerve to the short head of the Biceps femoris comes from the common peroneal part of the sciatic, while the other muscular branches arise from the tibial portion, as may be seen in those cases where there is a high division of the sciatic nerve.

The muscular branch eventually gives off the tibial nerve and common peroneal nerve, which innervates the muscles of the (lower) leg. The tibial nerve goes on to innervate muscles of the foot.

[edit] Trivia

• Sciatic nerves from frogs and rats are often used in physiology experiments on nerve conduction because this nerve is large, and easily dissected and manipulated.

• In the Jewish dietary laws (Kashrut), the hindquarters of a mammal are not kosher unless the sciatic nerve and the fat surrounding it are removed (Genesis 32).

[edit] Pathology

Pain caused by a compressed or damaged sciatic nerve is called sciatica

Understanding sciatica
Low back pain and/or leg pain that usually travels down the large sciatic nerve, from the lower back down the back of each leg, is generally referred to as sciatica and is fairly common. This pain can be caused when a nerve root in the lower spine that helps form the sciatic nerve is pinched or irritated.

Sciatica is usually caused by pressure on the sciatic nerve from a herniated disc (also referred to as a ruptured disc, pinched nerve, slipped disk, etc.) in the lumbar spine. The problem is often diagnosed as a "radiculopathy", meaning that a disc has protruded from its normal position in the vertebral column and is putting pressure on the radicular nerve (nerve root) in the lower back, which forms part of the sciatic nerve.

Sciatica occurs most frequently in people between 30 and 50 years of age. Often a particular event or injury does not cause sciatica, but rather it may develop as a result of general wear and tear on the structures of the lower spine. The vast majority of people who experience sciatica get better with time (usually a few weeks or months) and find pain relief with non-surgical treatments.

Understanding sciatica pain
For some people, the pain from sciatica can be severe and debilitating. For others, the pain might be infrequent and irritating, but has the potential to get worse. Usually, sciatica only affects one side of the lower body, and the pain often radiates from the lower back all the way through the back of the thigh and down through the leg. Depending on where the sciatic nerve is affected, the pain may also radiate to the foot or toes.

One or more of the following sensations may occur as a result of sciatica:

• Pain in the rear or leg that is worse when sitting

• Burning or tingling down the leg

• Weakness, numbness or difficulty moving the leg or foot

• A constant pain on one side of the rear

• A shooting pain that makes it difficult to stand up

• Low back pain may be present along with the leg pain, but usually the low back pain is less severe than the leg pain

While sciatica can be very painful, it is rare that permanent nerve damage (tissue damage) will result. Most sciatica pain syndromes result from inflammation and will get better within two weeks to a few months. Also, because the spinal cord is not present in the lower (lumbar) spine, a herniated disc in this area of the anatomy does not present a danger of paralysis.

Symptoms that may constitute a medical emergency include progressive weakness in the leg or bladder/bowel incontinence. Patients with these symptoms may have cauda equina syndrome and should seek immediate medical attention. In general, patients with complicating factors should contact their doctor if sciatica occurs, including people who: have been diagnosed with cancer; take steroid medication; abuse drugs; have unexplained, significant weight low; or have HIV.

Any condition that causes irritation or impingement on the sciatic nerve can cause the pain associated with sciatica. The most common cause is a lumbar herniated disc. Other common causes of sciatica include lumbar spinal stenosis, degenerative disc disease, or isthmic spondylolisthesis.

Sciatica medical definition
To clarify medical terminology, the term sciatica (often misspelled as ciatica or siatica) is often used very broadly to describe any form of pain that radiates into the leg. However, this is not technically correct. True sciatica occurs when the sciatic nerve is pinched or irritated and the pain along the sciatic nerve is caused by this nerve (radicular pain). When the pain is referred to the leg from a joint problem (called referred pain), using the term sciatica is not technically correct. This type of referred pain (e.g. from arthritis or other joint problems) is quite common.

Sciatica treatments
Sciatica nerve pain is caused by a combination of pressure and inflammation on the nerve root, and treatment is centered on relieving both of these factors. Typical sciatica treatments include:

• Non-surgical sciatica treatments, which may include one or a combination of medical treatments and alternative (non-medical) treatments, and almost always includes some form of exercise and stretching. The goals of non-surgical treatments should include both relief of sciatica pain and prevention of future sciatica problems.

• Sciatica surgery, such as microdiscectomy or lumbar laminectomy and discectomy, to remove the portion of the disc that is irritating the nerve root. This surgery is designed to help relieve both the pressure and inflammation and may be warranted if the sciatic nerve pain is severe and has not been relieved

Sciatica first aid

The term sciatica (sometimes misspelled "ciatica" or "siatica") is used to describe pain that radiates down the course of the sciatic nerve, which starts from each side of the lower back, extends down the back of the thigh, and into the foot.

This type of pain is caused by compression of nerve roots in the lower part of the spine, which merge together to form the sciatic nerve in the pelvis. Pain may result from a variety of conditions, including disc problems. The good news, however, is that most cases of sciatica are not serious and will get better within a few days or weeks.

When the sciatica pain flares up, it is helpful to know several options that can be used to help alleviate the pain and discomfort and help you to quickly return to your normal activity.

Cold and heat treatment for sciatica
Ice and heat sources are easily available, inexpensive, and usually quite effective in treating sciatica.

• A cold pack or ice application can reduce inflammation and numb sore tissue, alleviating some of the pain in the sciatic nerve. This should be used initially when pain is sharp and intense, usually for 2 to 7 days, depending on the severity of the pain.
• Heat dilates blood vessels, increasing the flow of oxygen and nutrients to the area, which assists in healing. Applying heat also stimulates sensory receptors in the skin, so the brain focuses less on the pain of sciatica. This is best used after the acute, sharp pain has subsided, typically 3 to 7 days after the start of the condition.

For some people, alternating between ice and heat is the most effective sciatica treatment.

One option for applying cold is to utilize an ice massage. This is most easily accomplished by freezing water in a paper cup and after its frozen, cut the top half of the cup away exposing the ice (like a Popsicle). The ice cup is then applied directly to the skin, usually in a circular motion over the course of the painful area. There are 4 stages of cooling, of which the second to last is a burning sensation, similar to eating ice cream too quickly. The last stage is numbness after which time frostbite can occur so stop when the burning turns into numbness. This process usually takes between 3 to 6 minutes, depending on the thickness of the area being treated. 

The ice massage can be given by someone else with the patient lying on his or her stomach or side. The ice should be gently applied to the six-inch area where the pain is felt, and massaged using a circular motion, using care to avoid the bony portion of the spine. The goal is to numb the area of discomfort, at which time gentle, minimal movements can be made to stretch out the sciatic nerve and relieve the compression that is causing the pain. When the numbness wears off, the ice can be re-applied and the procedure repeated. This treatment can be done two or three times a day.

An ice pack is another approach where the ice is wrapped it in a towel or, a commercial ice pack can be used. This is usually kept in one spot, such as the low back, for 15 to 20 minutes per application, and repeated for three times (15 minutes on-off-on-off-on, which takes 1 hour, 15 minutes = 1 session). For sciatica, the pack is placed over the lower back as that is where the sciatic nerve is usually pinched. Several sessions can be performed throughout the day.

Heat should also be applied carefully to avoid burning. The temperature of the heating pad, hot water bottle, (or water for a bath), should be warm, not hot, and is frequently buffered with a towel so the skin does not get too moist. In addition to the benefits stated above, heat relaxes the muscles, which again, allows for some pain relief, allowing the patient to stretch out the sciatic nerve and diminish the compression that is causing the sciatica.

Medications to treat sciatic pain
The pain associated with sciatica may also be reduced and sometimes relieved with the use of over-the-counter or prescription medications. Because some of the pain is coming from inflammation of the sciatic nerve, treatment using non-steroidal anti-inflammatory drugs (NSAID's) can be very effective. Aspirin can also help reduce the inflammation, but NSAID's have fewer gastrointestinal side effects (such as gastritis or ulcers).

There are many options to consider when choosing NSAID's. Each is somewhat different and it is always advisable to discuss the benefits and drawbacks of each with a physician or pharmacist. NSAID options include:

• Ibuprofen—such as Advil, Nuprin, Motrin
• Naproxen—such as Naprosyn, Aleve
• COX-2 inhibitors—such as Celebrex or Bextra (which require a prescription)

Acetaminophen (such as Tylenol) can also be used for relief of sciatic pain. Because NSAID's and acetaminophen work differently, the two medications may be taken at the same time or staggered (i.e., NSAID's followed by acetaminophen, etc.).

Other, stronger pain medications are also available through a prescription from a physician and may be necessary to help alleviate the pain from irritation to the sciatic nerve.

Exercise for long-term pain relief
Once pain control has been achieved, gentle stretching of the affected area, and low-impact exercise, (such as walking two to three miles) will help bring healing nutrients to the affected area and help to restore function. As with any back treatment, care should be taken to not further aggravate the situation. It is always advisable to consult with a doctor with any questions or concerns that may arise during the course of care.

For long-term relief of sciatica pain, most experts agree that a regular routine of stretching and exercise is crucial.

• Stretching. Patients may find it takes several weeks or months to develop flexibility in the spine and soft tissues, but may also find that the stretching helps bring sustained pain relief. The spinal column and its contiguous muscles, ligaments and tendons are all designed to move, and limitations in this motion can accentuate pain and make one more susceptible to re-injury.
  
  Stretching exercise should focus on increasing flexibility in the disc, muscles, ligaments, and tendons. Additionally, it is important to stretch muscles not directly involved with the injured area, such as the arms and legs. For example, the hamstring muscles play a major role in lower back pain, as it is clear that hamstring tightness limits motion in the hip, which increases stress across the low back, especially during forward bending.

• Strengthening. Building strength is also important to help prevent and/or lessen future recurrences of sciatic pain. Specific exercises designed to strengthen the “core” or trunk muscles are most important in the management of low back pain.
  
  Depending on the underlying cause of sciatica (such as a herniated disc vs. a degenerated disc), different exercises may be prescribed. Two common forms of strengthening exercises to treat sciatica are McKenzie exercises and Dynamic Lumbar Stabilization exercises. Learning which exercises to do, as well as how to do them correctly, is typically best learned with the help of a qualified spine specialist.

Manipulation and physical therapy
Another treatment option that can be helpful for many causes of for sciatica is manipulation by a qualified health care provider (most commonly a chiropractor or an osteopath). The type of manipulation, amount of force, the direction of the manipulation and the frequency of application are taken into consideration when managing patients complaining of sciatica. Combining this with various forms of physical therapy such as exercise therapies can be very effective.

Other considerations with sciatic pain
Though uncommon, when the sciatic condition worsens, it is most important to obtain a prompt evaluation. This is especially true if progressive muscle weakness, foot drop, or loss of bowel or bladder control occur, as these symptoms require immediate emergency attention and permanent problems can result if not managed promptly. In general, whenever questions arise about the course of care and associated signs and symptoms, health care provision should be obtained and the questions answered.

The good news is that most cases of sciatica will resolve naturally within a few weeks. The treatments described here can help alleviate pain until things return to normal, and help speed recovery, as well as avoid recurrence. Every patient is different of course, and not all sciatica treatments will work for all cases of sciatica.

Sciatic pain can be mild and intermittent, but this type of pain along the large sciatic nerve can also be searing and unbearable. For severe cases of sciatic pain, it makes sense to get a firm or definitive diagnosis regarding the underlying cause of the sciatica (e.g. a herniated disc, degenerative disc disease, spondylolisthesis) and discuss additional treatment options with a spine specialist. In addition to the remedies discussed above, there are a wide variety of additional treatment options, including injections, surgery, and more.