The sensitivity of these signs for meningitis is poor: neck stiffness 30% and Kernig’s and Brudzinski’s signs 5% each (1). Therefore, their absence does not exclude the possibility of meningitis. Although their specificities may be comparatively better (neck stiffness 68%, and Kernig’s and Brudzinski’s signs 95% each), the positive and negative predictive values of these signs generally leave a lot to be desired and their likelihood ratios (both positive and negative) are poor (near 1.0) (1).
The poor sensitivities of Kernig’s and Brudzinski’s signs may be related to the fact that the original research papers published over 100 years ago involved primarily children with severe bacterial or tuberculous meningitis, a population that is quite different than today’s elderly or immunocompromised patients (2) who may present earlier during their course of disease. Thus, the decision to perform a lumbar puncture should be based primarily on factors other than these signs.
- Thomas KE, Hasbun R, Jekel J, et al. The diagnostic accuracy of Kernig’s sign, Brudzinski’s sign, and nuchal rigidity in adults with suspected meningitis. Clin Infec Dis 2002;35:46-52. https://www.ncbi.nlm.nih.gov/pubmed/12060874
- Mehndiratta M, Nayak R, Garg H, et al. Appraisal of Kernig’s and Brudzinski’s sign in meningitis. Ann Indian Acad Neurol. 2012 Oct-Dec; 15(4): 287–288. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3548367