Meningitis is a common life-threatening medical emergency caused by infectious and non-infectious agents. Rapid and accurate evaluation utilizing a comprehensive history and clinical examination is helpful to guide further specific investigation and treatment.
Kernig’s sign, Brudzinski’s sign and nuchal rigidity are bedside diagnostic signs used to evaluate suspected cases of meningitis. The presence of meningeal irritation, however, does not indicate meningitis.
Vladimir Mikhailovich Kernig (1840-1917) first described the ‘meningeal sign’ also known as Kernig’s sign. He observed that many patients with meningitis had restriction in passive extension at the knee because of spasm of the hamstring muscles. To elicit the Kernig’s sign, the patient is kept in a supine position. The hip and knee are flexed to a right angle, and then the knee is slowly extended by the examiner. The appearance of resistance or pain during extension of the patient’s knees beyond 135 degrees constitutes a positive Kernig’s sign. Kernig in his original description did not consider pain as a required component of the maneuver. However, many clinicians include pain as an essential component of a positive sign.
Josef Brudzinski (1874-1917), described 4 maneuvers for the clinical diagnosis of meningitis: The obscure cheek sign, symphyseal sign, Brudzinski’s reflex and the most popular Brudzinski neck sign. The Brudzinski’s neck sign is performed with the patient in the supine position. The examiner keeps one hand behind the patient’s head and the other hand on the patient’s chest in order to prevent the patient from rising. Reflex flexion of the patient’s hips and knees after passive flexion of the neck constitutes a positive Brudzinski sign. It has been proposed that in patients with meningitis, passive flexion of the neck stretches the nerve roots through the inflamed meninges, leading to pain and flexion movements of lower extremities.
From the outcome of several studies, it is appears that both Kernig’s and Brudzinski’s signs are not very specific for detecting meningitis and, therefore, when absent, should not be inferred as there being no evidence of meningitis. However, although the specificity is quite low, the high sensitivity suggests that if Kernig’s or Brudzinski’s sign is present, then there is a high likelihood for meningitis. The two signs, Kernig’s and Brudzinski’s, are often performed together in clinical practice.
For a comprehensive history of the discovering physicians, a complete description of the clinical tests (with illustrations) and discussions of the outcome of both clinical tests, I highly recommend this link.
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