Sciatica

Sciatica is a term whose Chinese-character name means “sciatic nerve pain.” It encompasses pain and tingling along the back of the leg, where the sciatic nerve runs. Like fever or a cough, it is a symptom name shared by several causes, so saying “I have sciatica” is closer to describing “this is the pattern of my pain.” In clinical practice, it is sometimes used almost interchangeably with Lumbar radiculopathy.

Its main feature is that the pain does not stay in one spot in the lower back but radiates down the leg. Pain that spreads along the course of a nerve in this way is called Radicular pain. It usually affects one leg, either the left or the right, and is common enough that many people experience it at least once in their lives. Some sources estimate that roughly 12–40% of people experience it during their lifetime, though estimates vary considerably depending on the survey method.

The sciatic nerve is the thickest and longest peripheral nerve in the body. Several nerve roots emerging from the lower lumbar spine and sacrum (roughly levels L4 to S3) come together within the pelvis to form a thick bundle. This bundle exits through a large opening at the back of the pelvis and passes near the Piriformis muscle deep in the buttock. It usually passes below the piriformis, but some people have an anatomical variation in which part of the nerve passes through the muscle.

It then travels down the back of the thigh and divides into two branches behind the knee.

• Tibial nerve — Travels along the back of the calf and continues to the sole of the foot.
• Common fibular nerve — Curves around the head of the fibula on the outside of the knee and continues to the outer shin and top of the foot.

Because it is long and formed from nerve roots at several levels, the area of discomfort can vary among the buttock, back of the thigh, calf, top of the foot, and sole, depending on where it is irritated. The dermatome in which symptoms spread can help estimate which nerve root level is involved, but the boundaries overlap somewhat and vary from person to person, so they do not always match exactly.

When a nerve or its root is irritated somewhere along its pathway, symptoms can radiate into the leg. The underlying causes can be considered in two broad groups.

When it starts in the spine

• Lumbar disc herniation — This is the most frequently cited underlying cause of sciatica. Displaced disc material presses on or irritates a nearby nerve root. In addition to pressure, the inflammatory response caused by disc material contributes to symptoms, so the appearance on imaging does not necessarily correspond to the severity of pain.
• Lumbar spinal stenosis — As people age, ligaments thicken and bones change, narrowing the Spinal canal through which the nerves pass. It may be accompanied by Neurogenic claudication, in which the legs feel heavy during walking and require a rest, with relief when bending forward at the waist.
• Spondylolisthesis and other conditions — Changes in the alignment of the vertebrae can also affect the nerve passageways.

When it starts in the buttock

In this form, the main trunk of the sciatic nerve passing through the buttock is irritated, rather than a nerve root. Piriformis syndrome is the concept that the piriformis muscle deep in the buttock irritates the nerve passing nearby. A broader framework called Deep gluteal syndrome, which considers the entire deep gluteal space, is also used. Similar symptoms can occur during periods when the pelvis and posture change, such as pregnancy.

Leg pain that resembles sciatica

Not all pain in the buttock or thigh comes from a nerve root. Referred pain, which starts in a muscle or joint but is felt as a broad, dull ache elsewhere, can also spread into the leg. The distinction is that radicular pain shoots along the course of a nerve in a narrow band, whereas referred pain is more widespread and feels like a deep ache.

• Pain radiating into one leg — A typical pattern is a line of pain starting in the lower back or buttock and continuing through the back of the thigh, calf, and foot.
• Tingling and prickling — Paresthesia or a sharp tingling sensation may occur along with the pain. Many people describe it as Electric shock-like pain, as though electricity were running through the area.
• Severity that changes with posture — Symptoms may become more noticeable when sitting for a long time, bending forward, or bracing the abdomen during a cough or sneeze. Conversely, some people feel better when walking or changing position. There is considerable individual variation.

Pain intensity is not determined solely by how much the tissues have changed. Activity levels, sleep, stress, and how sensitive the nerves are all interact to shape the experience of pain. That is why two people with the same imaging findings can have very different experiences.

Sciatica often gradually becomes more comfortable over time. When a disc herniation is the cause, the displaced disc material has also been reported to shrink naturally over time. However, the time this takes varies considerably: some people feel better within a few weeks, while others have symptoms for longer.

• Avoid staying in bed too long — You may want to rest when you are in pain, but many recommendations suggest that walking and moving as much as your pain allows can help. Find a comfortable position to rest in, but try not to spend the whole day lying down.
• Change position often — Many people find that sitting in one position for a long time worsens their symptoms. Try getting up about once every 30 minutes for a gentle walk.
• Apply warmth — Many people find that a warm compress on the buttock and lower back helps the surrounding muscles relax and makes them feel more comfortable.
• Gentle walking — Try starting with a slow walk on level ground. If the sensation radiating down your leg gradually worsens while walking, try reducing the distance.
• Take care when lifting heavy objects — Rather than bending at the waist to lift, bend your knees and keep the object close to your body as you lift it.
• Exercises that gently move the nerves — Exercises based on Neurodynamics and neural mobilization, which help nerves glide between the surrounding tissues, are also used. It is safer to learn the movements from a professional when starting out.

In most cases, it is fine to monitor symptoms calmly, but if you notice unusual signs such as the following, get checked at a nearby hospital or clinic.

• Your leg feels weak, or you feel unable to lift the front of your foot
• You have difficulty urinating or passing stool, or reduced sensation around the anus and groin
• You have a fever, sudden weight loss, or severe pain that continues at night even when resting
• Symptoms begin after a fall or impact
• Symptoms do not improve after several weeks and are getting progressively worse