The Lasègue sign is a clinical sign that belongs to the neurological and orthopedic examination methods. It was named after the French doctor Ernest-Charles Lasègue. The Lasègue sign, or Lasègue test, is based on the triggering of a stretching pain of the spinal nerve roots L4 to S1 and the sciatic nerve. A positive Lasègue sign is an indication of inflammation in the area of these nerve roots or the sciatic nerve. Since it is also positive in the case of meningitis, it is also performed in the case of suspected meningitis (inflammation of the meninges).
Causes for a positive Lasègue sign
Many orthopedic and neurological diseases require an examination of the Lasègue sign. Possible causes of a positive Lasègue’s sign are inflammation in the area of the spinal nerve roots L4 to S1 and inflammation or irritation of the sciatic nerve. A frequent cause of such nerve damage in the area of the spinal nerve roots is a herniated disc.
The sciatic nerve itself can be damaged in its course and cause sciatica/sciatica syndrome, also known as lumbago or lumbago, or it can be damaged when it emerges as spinal nerve S1 in the context of a herniated disc. Theoretically, the S1 nerve is damaged, which is not yet called the sciatic nerve by definition. This means that a positive Lasègue sign indicates the location of a possible disease. Furthermore, the Lasègue sign can be positive in the case of meningitis. In this case, the meninges are irritated and are stretched by the movement, causing a sharp pain.
Causes for a negative Lasègue sign
A negative Lasègue sign occurs in principle in healthy people and in those patients who do not suffer from nerve root compression syndrome in the area of the nerve roots L4 to S1 or from meningitis. Herniated discs affecting higher spinal nerve roots are not detected with this clinical examination mark.
What is a crossed Lasègue sign
In case of a crossed Lasègue sign, the unaffected leg is examined. The patient lies on his back and the examiner lifts the non-affected leg in an extended position. A positive Lasègue’s sign in the crossed Lasègue’s sign means that a pain suddenly shoots into the reciprocal leg lying on the couch and not lifted, which can spread to the motor/sensitive area of the affected nerve root. This means that the crossed Lasègue test works like the “normal” Lasègue test, with the difference that the unaffected leg is lifted and pain is caused in the affected leg. A positive Lasègue sign in the crossed Lasègue test means that there is root irritation of the spinal nerve roots L4 to S1, the sciatic nerve or an irritation of the meninges on the opposite side.
