Sciatica is a term that describes pain radiating along the path of the sciatic nerve, which is the longest nerve in the human body. It originates in the lower back, extends through the buttocks, and runs down each leg. Anatomically, the sciatic nerve is composed of nerve roots from the lower spinal cord, specifically from the lumbar spine (L4, L5) and the sacral spine (S1, S2, S3).
Causes and Anatomical Concerns
Herniated Disc: One of the most common causes of sciatica is a herniated or slipped disc in the lower spine. The intervertebral discs act as cushions between the vertebrae. When a disc herniates, its inner gel-like core can bulge out, compressing or irritating the adjacent sciatic nerve roots. This compression leads to pain, numbness, and weakness in the affected leg.
Spinal Stenosis: Spinal stenosis refers to the narrowing of the spinal canal or the foramina (the openings through which nerve roots exit the spine). This narrowing can put pressure on the sciatic nerve roots, leading to sciatica symptoms.
Piriformis Syndrome: The piriformis muscle is located deep in the buttock, near the top of the hip joint. In some cases, the sciatic nerve passes through or under this muscle. If the piriformis muscle becomes tight or spasms, it can compress the sciatic nerve, causing sciatica.
Spondylolisthesis: This condition occurs when one vertebra slips forward over the one below it, which can lead to compression of the sciatic nerve roots, resulting in sciatica.
Degenerative Disc Disease: Over time, the intervertebral discs can degenerate, losing water content and becoming less flexible. This degeneration can lead to disc herniation or other issues that may compress the sciatic nerve.
Symptoms
- Radiating Pain: The hallmark symptom of sciatica is a sharp, shooting pain that starts in the lower back or buttocks and radiates down the back of the thigh and calf, sometimes reaching the foot.
- Numbness and Tingling: Patients often experience numbness, tingling, or a burning sensation along the path of the sciatic nerve.
- Muscle Weakness: Sciatica can cause weakness in the affected leg, making it difficult to stand or walk.
Anatomical Concerns
The anatomical structures involved in sciatica, including the lumbar spine, sacral spine, and the muscles and ligaments surrounding them, are critical for maintaining posture and enabling movement. Prolonged compression or irritation of the sciatic nerve can lead to chronic pain and, in severe cases, permanent nerve damage.
Loss of Sensation or Motor Function: Persistent sciatica can lead to loss of sensation or motor function in the affected leg, which may result in difficulty performing daily activities.
Bladder or Bowel Dysfunction: In rare cases, sciatica associated with severe spinal stenosis or cauda equina syndrome can lead to loss of control over bladder or bowel functions. This is a medical emergency and requires immediate attention.
Various special tests for sciatica
1. Straight Leg Raise (SLR) Test:
- Procedure: The patient lies supine, and the examiner lifts the patient's leg with the knee straight.
- Positive Sign: Pain radiating down the leg when the leg is raised between 30° and 70° indicates possible sciatic nerve irritation.
2. Lasegue's Test (Variation of SLR):
- Procedure: Similar to the SLR, but after pain is elicited, the leg is slightly lowered, and the foot is dorsiflexed.
- Positive Sign: Increased pain upon dorsiflexion indicates sciatic nerve involvement.
Bragard's Sign:
- Procedure: Following a positive SLR, the leg is lowered just below the point of pain, and the foot is dorsiflexed.
- Positive Sign: Reproduction of pain with dorsiflexion suggests sciatica.
4. Crossed Straight Leg Raise (Well Leg Raise) Test:
- Procedure: The opposite, unaffected leg is raised while the patient is lying supine.
- Positive Sign: Pain radiating down the affected leg (the one not being raised) indicates a more specific sign of disc herniation causing sciatica.
5. Slump Test:
- Procedure: The patient sits with legs hanging off the table, slumps forward, and then straightens one leg while dorsiflexing the foot.
- Positive Sign: Pain or discomfort in the sciatic nerve distribution during the maneuver suggests nerve root tension.
6. Bowstring Test (Cram Test):
- Procedure: After performing the SLR test, the knee is flexed slightly, relieving the pain, then pressure is applied to the popliteal fossa.
- Positive Sign: Reproduction of sciatica symptoms indicates nerve tension.
7. Piriformis Test:
- Procedure: The patient lies on the unaffected side, and the examiner flexes the hip and knee of the affected leg, then pushes the knee downward.
- Positive Sign: Pain in the buttock and down the leg suggests piriformis syndrome, which can mimic sciatica.
Femoral Nerve Stretch Test:
- Procedure: The patient lies prone, and the examiner flexes the knee while extending the hip.
- Positive Sign: Pain in the anterior thigh suggests nerve root compression in the upper lumbar region, which can sometimes present as sciatica.
9. Valsalva Maneuver:
- Procedure: The patient takes a deep breath and bears down as if trying to have a bowel movement.
- Positive Sign: Increased pain due to increased intrathecal pressure may indicate nerve root compression.
These tests help in identifying the presence of sciatica and differentiating it from other conditions that may mimic its symptoms.
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