From the Guidelines
Significance of a Positive Kernig's Sign
A positive Kernig's sign is a significant indicator of meningitis, particularly in children, suggesting irritation of the meninges 1.
Clinical Implication
To check for Kernig's sign, the patient should lie supine with the hip flexed at 90 degrees, and then the knee is slowly extended while keeping the hip flexed. If the patient experiences resistance or pain when extending the knee beyond 90 degrees, or if they are unable to fully extend the knee due to discomfort, the Kernig sign is considered positive. However, it's crucial to note that Kernig's sign and Brudzinski's sign should not be relied upon for diagnosis due to their low sensitivity 1.
Diagnostic Considerations
The sensitivity of Kernig's sign for the diagnosis of bacterial meningitis is relatively low, around 53% 1, indicating that a negative Kernig's sign does not rule out meningitis. Clinical characteristics, including Kernig's sign, cannot be used to differentiate between bacterial and viral/aseptic meningitis reliably 1.
Management
If a positive Kernig sign is observed, especially in the context of other symptoms such as fever, headache, and neck stiffness, it is recommended to immediately seek medical attention for further evaluation. Potential treatments may include antibiotics such as ceftriaxone or vancomycin, and a lumbar puncture for cerebrospinal fluid analysis should be considered 1.
Key Points
- Kernig's sign is associated with meningitis, particularly in children.
- The sign has low sensitivity and should not be solely relied upon for diagnosis.
- Immediate medical attention is required if meningitis is suspected, regardless of the presence or absence of Kernig's sign.
- Further diagnostic tests, such as lumbar puncture, are necessary for confirmation and to guide appropriate treatment.
From the Research
Significance of a Positive Kernig's Sign
A positive Kernig's sign is a clinical indication of meningeal irritation, which can be a sign of meningitis. The significance of a positive Kernig's sign is as follows:
- It is a specific test for meningeal irritation, but it is not pathognomonic for meningitis 2
- The presence of Kernig's sign, along with other signs of meningeal irritation, can raise the likelihood of meningitis 3
- Kernig's sign has a relatively high positive predictive value (77%) for meningitis, but its sensitivity is low (27%) 4
- In adults, specific tests like Kernig's sign may not affect the reliability of the diagnosis of meningitis, and its diagnostic value is probably limited 5
- Familiarity with all the meningeal signs, including Kernig's sign, is desirable for early diagnosis and treatment of meningitis 6
Clinical Features and Diagnostic Accuracy
The diagnostic accuracy of clinical symptoms and signs in children with meningitis is limited. Key points include:
- Classic clinical diagnostic signs, including Kernig's sign, have limited value in establishing the diagnosis of meningitis in children 4
- No isolated clinical feature is diagnostic, and the most accurate diagnostic combination is unclear 3
- The absence of meningeal signs can lower the likelihood of meningitis, while the presence of certain signs, such as bulging fontanel or neck stiffness, can raise the likelihood 3
Specificity and Sensitivity of Kernig's Sign
The specificity and sensitivity of Kernig's sign vary: