From the Guidelines
Kernig's sign is present in approximately 11% of patients with bacterial meningitis, as reported in a recent study 1. This sign, which involves pain and resistance when attempting to extend the knee while the hip is flexed at 90 degrees, has low diagnostic accuracy for prediction of cerebrospinal fluid (CSF) pleocytosis, with a sensitivity of 11% 1. The frequency of Kernig's sign varies significantly based on the patient population, but its presence or absence should not be used alone to rule out meningitis, as its sensitivity is low and its absence does not exclude the diagnosis 1. Some key points to consider when evaluating Kernig's sign in patients with suspected meningitis include:
- The classic triad of fever, neck stiffness, and altered mental status is reported in only 41-51% of patients with bacterial meningitis 1
- A petechial rash is identified in 20-52% of patients and is indicative of meningococcal infection in over 90% of patients 1
- Kernig's sign and other meningeal signs, such as Brudzinski's sign, have low sensitivity and specificity for diagnosing meningitis, and should be used in conjunction with other clinical findings and laboratory tests to make an accurate diagnosis 1
- A complete clinical assessment, including neurological examination and appropriate laboratory testing, is essential for accurate diagnosis of meningitis 1.
From the Research
Frequency of Kernig Sign in Meningitis
- The frequency of Kernig sign in patients with meningitis is not explicitly stated in the provided studies, but its diagnostic accuracy and usefulness are discussed.
- A study published in 2002 2 found that Kernig's sign had a sensitivity of 5% and a likelihood ratio for a positive test result of 0.97, indicating that it did not accurately discriminate between patients with meningitis and those without.
- Another study from 2010 3 also found that Kernig's sign, along with other physical signs of meningeal irritation, did not help clinicians rule in or rule out meningitis accurately.
- A 2017 study 4 mentions that examination maneuvers such as Kernig sign or Brudzinski sign may not be useful to differentiate bacterial from aseptic meningitis due to variable sensitivity and specificity.
Diagnostic Accuracy of Kernig Sign
- The diagnostic accuracy of Kernig's sign is generally considered to be low, with sensitivity and specificity values that do not support its use as a reliable diagnostic tool for meningitis 3, 2.
- A study from 1987 5 discusses the original description of Kernig's sign and its evolution over time, but does not provide information on its frequency or diagnostic accuracy in meningitis.
- The 2004 study 6 focuses on clinical indicators of acute bacterial meningitis in children and does not specifically address the frequency or diagnostic accuracy of Kernig's sign.
Clinical Implications
- The low diagnostic accuracy of Kernig's sign and other physical signs of meningeal irritation highlights the importance of relying on cerebrospinal fluid analysis and other diagnostic tests to confirm the presence of meningitis 4, 3, 2.
- Clinicians should be cautious when interpreting physical signs of meningeal irritation and should not rely solely on these signs to diagnose or rule out meningitis 3, 2.