Lasègue Sign – Meaning, Test and Diagnosis
The Lasègue sign is a clinical test used to detect sciatica or a herniated disc. A positive result occurs when raising the straightened leg causes radiating pain along the sciatic nerve.
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The Lasègue sign is a clinical test used to detect sciatica or a herniated disc. A positive result occurs when raising the straightened leg causes radiating pain along the sciatic nerve.
What Is the Lasègue Sign?
The Lasègue sign (also known as the Lasègue test or straight leg raise test) is a clinical examination procedure used in neurology and orthopedics. It helps detect irritation or compression of the sciatic nerve or the lumbar nerve roots. The test is named after the French neurologist Ernest-Charles Lasègue (1816–1883), who first described it in the 19th century.
How the Test Is Performed
The patient lies flat on their back. The examiner slowly lifts the patient's straightened leg without bending the knee. The angle at which pain occurs is noted and recorded.
- A positive Lasègue sign is present when radiating pain along the course of the sciatic nerve occurs at an angle of less than 60–70 degrees.
- Pain occurring only at angles greater than 70 degrees is generally not considered pathological in terms of nerve root irritation.
- The crossed Lasègue test (contralateral straight leg raise) is positive when lifting the healthy leg causes pain in the affected leg, suggesting a large medial disc herniation.
Causes of a Positive Test
A positive Lasègue sign may indicate various underlying conditions:
- Lumbar disc herniation (prolapsed nucleus pulposus), particularly at the L4/L5 or L5/S1 level
- Spinal stenosis (narrowing of the spinal canal)
- Piriformis syndrome (irritation of the sciatic nerve by the piriformis muscle)
- Inflammatory or tumor-related processes affecting the nerve roots
- Spondylolisthesis (vertebral slippage)
Symptoms Associated with a Positive Lasègue Sign
Typical complaints suggesting a positive Lasègue sign include:
- Radiating pain from the lower back through the buttocks into the leg or foot (sciatica)
- Tingling or numbness in the leg
- Muscle weakness in the affected leg
- Worsening of pain with coughing, sneezing, or straining
Diagnosis and Clinical Relevance
The Lasègue sign is an important component of the physical neurological examination for low back pain. It is commonly used alongside other tests:
- Bragard sign: Additional dorsiflexion of the foot increases pain and enhances the specificity of the test.
- Kernig sign: Tests knee extension with the thigh raised – relevant when meningitis is suspected.
- Imaging studies such as MRI (magnetic resonance imaging) or CT (computed tomography) of the lumbar spine for diagnostic confirmation.
The sensitivity of the Lasègue test for lumbar disc herniation is approximately 80–90%, while its specificity is around 40–60%. It is therefore a sensitive but non-specific sign and must always be interpreted within the broader clinical context.
Treatment When the Test Is Positive
Treatment depends on the underlying cause:
- Conservative therapy: Physiotherapy, targeted exercise programs, heat treatment, pain medication (e.g., NSAIDs, muscle relaxants)
- Interventional procedures: Periradicular infiltrations (targeted corticosteroid injections near the nerve root)
- Surgical treatment: In cases of therapy-resistant symptoms or neurological deficits (e.g., paralysis, bladder or bowel dysfunction), surgical intervention such as microdiscectomy may be necessary.
References
- Krämer, J. & Grifka, J. (2007). Orthopädie und Unfallchirurgie. Springer Medizin Verlag.
- Deyo, R. A. et al. (1992). What can the history and physical examination tell us about low back pain? JAMA, 268(6), 760–765.
- World Health Organization (WHO). Musculoskeletal conditions – Low back pain. Available at: https://www.who.int/news-room/fact-sheets/detail/musculoskeletal-conditions
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