The classic triad of fever, meningismus (stiff neck), and altered mental status only occurs in 44% of cases of acute bacterial meningitis (ABM).
Headache is a much more common presenting complaint with ABM.
The sensitivity and specificity of Kernig and Brudzinski signs are suboptimal, making their presence or absence of little diagnostic value.
References
Van de Beck, D, et al. "Clinical features and prognostic factors in adults with bacterial meningitis." New England Journal of Medicine. 2004; 351 (18); 1849-59.
Thomas KE, et al. "The diagnostic accuracy of Kernig's sign, Brudzinski's sign, and nuchal rigidity in adults with suspected meningitis." Clinical Infectious Diseases. 2002; 35(1); 46-52.
