Kernig Sign

Excerpt

Kernig sign is one of the eponymous clinical signs of meningitis. This test is typically performed in patients while supine and is described as resistance (or pain) with passive extension of the knees. This resistance is thought to be due to meningeal inflammation in the setting of meningitis or other clinical entities that may irritate the meninges. Since its conception in the 19th century, the clinical value of the Kernig sign has been more thoroughly explored. It remains a commonly performed maneuver in cases of suspected meningitis.

Background

Kernig sign was initially described in the 19th century by Russian physician Vladimir Kernig. Kernig observed that patients with bacterial or tuberculous meningitis could not wholly extend their legs while sitting upright. He continued investigating this finding over several decades of his career and first reported this sign at a medical congress in St. Petersburg in 1882. He presented his observations again in Copenhagen, Denmark, in 1884 and published the same year in Berliner Klinische Wochenschrift.

Kernig described a positive sign as the inability to extend the knees more than 135 degrees. In severe cases, patients could not extend their knees past 90 degrees. The maneuver was performed with the patient seated upright with the hips flexed 90 degrees to the trunk. Kernig also described instances where patients could not extend their elbows in cases of meningitis. Kernig did not use the pain as a marker for a positive test. The presence of contracture or extensor spasm at the knee was considered a positive finding. He noted, however, that the clinical severity of meningitis was not always associated with the severity of contraction of the extremities.