What is the examination of meningeal signs, including nuchal rigidity, Kernig sign, and Brudzinski sign, in neurology and how are the clinical findings evaluated?

Examination of Meningeal Signs in Neurology

Critical Clinical Reality

Meningeal signs have poor diagnostic accuracy and should never be used to rule out meningitis—lumbar puncture remains mandatory when meningitis is suspected, regardless of whether these signs are present or absent. 1, 2, 3

Understanding the Diagnostic Limitations

The classic meningeal signs are notoriously unreliable:

• Nuchal rigidity has a sensitivity of only 30-31%, meaning approximately 70% of patients with confirmed meningitis will NOT have this finding 4, 1, 5
• Kernig's sign demonstrates a sensitivity of only 5-11% 4, 1, 5
• Brudzinski's sign shows a sensitivity of only 5-9% 4, 1, 5
• The "classic triad" of fever, neck stiffness, and altered mental status is present in only 41-51% of bacterial meningitis cases 4, 1, 2

Detailed Examination Techniques

Nuchal Rigidity (Neck Stiffness)

Technique: Test for resistance to passive flexion of the neck with the patient supine 2

Clinical findings:

• Positive when there is involuntary resistance to forward neck flexion
• This is the most commonly observed meningeal sign when present 2
• Sensitivity: 30-31%, Specificity: variable 1, 5
• Likelihood ratio for positive test: 0.94-1.33 (essentially no diagnostic value) 3, 5

Evaluation: Even when absent, this does NOT exclude meningitis—proceed with lumbar puncture if clinical suspicion exists 1, 3

Kernig's Sign

Technique: With the patient supine, flex the hip to 90 degrees, then attempt to extend the knee 6

Clinical findings:

• Positive when knee extension causes pain or resistance, with the patient unable to extend the knee beyond 135 degrees
• Note: The current technique differs from Kernig's original 1882 description 6
• Sensitivity: 5-11%, Specificity: 85-95% 1, 5, 7
• Likelihood ratio for positive test: 0.97-1.84 (no meaningful diagnostic value) 3, 5

Evaluation: High specificity but extremely low sensitivity means a positive test may suggest meningitis, but a negative test is meaningless 5, 7

Brudzinski's Sign

Technique: With the patient supine, passively flex the neck forward 6

Clinical findings:

• Positive when passive neck flexion causes involuntary flexion of the hips and knees
• Brudzinski originally described multiple signs; the "nape of the neck" sign is most commonly tested 6
• Contralateral leg signs (less familiar) may be present when the classic sign is absent 6
• Sensitivity: 5-9%, Specificity: 85-95% 1, 5, 7
• Likelihood ratio for positive test: 0.97-1.69 (no diagnostic value) 3, 5

Evaluation: Like Kernig's sign, extremely poor sensitivity makes this unreliable for excluding disease 5, 7

Jolt Accentuation Test

Technique: Ask the patient to rotate their head horizontally 2-3 times per second 4, 2

Clinical findings:

• Positive when horizontal head rotation worsens the patient's headache 4, 2
• Sensitivity: 40-70%, Specificity: 33-75% 3, 8, 7
• Likelihood ratio for positive test: 1.02-5.52 3, 8
• Despite earlier reports suggesting near 100% sensitivity, recent studies show many patients with confirmed meningitis test negative 7

Evaluation: Shows slightly better sensitivity than other meningeal signs but still cannot rule out meningitis when negative 8, 7

Clinical Algorithm for Suspected Meningitis

When to suspect meningitis (contingency/crisis standards): 4

• Severe headache
• Altered mental status (inability to answer two consecutive questions or follow two consecutive commands) 4
• Any meningeal signs (even if just one)
• Other neurological symptoms (seizures, focal deficits, cranial nerve signs) 4
• Fever with purpuric/petechial rash (suggests meningococcal disease in 92% of cases) 4

Critical action: Perform lumbar puncture unless contraindicated, regardless of presence or absence of meningeal signs 1, 2, 3

Special Population Considerations

Elderly Patients

• More likely to have altered consciousness than younger patients 4
• LESS likely to have neck stiffness or fever 4
• Higher risk for Listeria or pneumococcal disease 4

Immunocompromised Patients

• May have blunted inflammatory responses 1
• Absence of meningeal signs is particularly common 2
• Never rely on physical examination alone in this population 2

Neonates

• Often present with nonspecific symptoms rather than classic meningeal signs 1, 2

Critical Pitfalls to Avoid

1. Never rule out meningitis based on absent meningeal signs—approximately 50% of patients with confirmed meningitis will have negative physical examination findings 7

2. Do not delay lumbar puncture waiting for signs to develop—CSF examination is the cornerstone of diagnosis with the highest diagnostic accuracy 1

3. If bacterial meningitis is suspected and LP is delayed, start empirical antibiotics immediately after obtaining blood cultures 2

4. Combining multiple meningeal sign examinations may slightly decrease misdiagnosis risk, but still cannot reliably exclude disease 7

5. No published diagnostic algorithm based on clinical signs alone has 100% sensitivity for distinguishing bacterial from viral meningitis 1

The Bottom Line on Result Interpretation

CSF white blood cell count (>5 cells/μL) is the best diagnostic parameter for confirming meningitis, with an area under the curve of 0.95 1. Physical signs should prompt investigation but never provide reassurance when negative—the absence of meningeal signs does not reduce the need for lumbar puncture in patients with appropriate clinical suspicion 3, 5.