The Brudzinski sign is a bedside physical examination maneuver used to detect meningeal irritation, the inflammation of the membranes surrounding the brain and spinal cord. A clinician passively flexes the patient’s neck forward, and the test is considered positive when the patient involuntarily flexes their hips and knees in response. First described in the early twentieth century by a Polish pediatrician, the sign remains a staple of clinical teaching, though modern research has revealed that its real-world diagnostic accuracy is far more limited than many practitioners assume.
How the Test Is Performed
The patient lies flat on their back with legs extended. The examiner places one hand behind the patient’s head and gently lifts it, bringing the chin toward the chest. A positive Brudzinski sign occurs when that passive neck flexion triggers an involuntary bending of both hips and knees. The idea is straightforward: inflamed meninges are stretched by the neck movement, and the body reflexively draws the legs upward to relieve that tension along the spinal canal. In practice, the response can range from a subtle upward drift of the knees to a dramatic, clearly visible flexion of both legs.
The maneuver should be performed gently. If a patient is alert and experiencing severe headache or neck pain, forceful neck flexion is not only unnecessary but can be distressing. In patients with suspected spinal injury, the test is contraindicated entirely because passive neck flexion could worsen a cervical spine problem.
Why Inflamed Meninges Produce This Reflex
The meninges are three layers of tissue that wrap around the brain and spinal cord. When they become inflamed, whether from a bacterial or viral infection, blood in the cerebrospinal fluid, or another irritant, the tissue becomes swollen and exquisitely sensitive to stretch. Flexing the neck pulls the spinal cord slightly upward and tautens the already irritated meninges along the length of the spine. The body’s protective response is to shorten the distance the meninges have to stretch, and the fastest way to do that is to flex the hips and knees, which relaxes the lower portion of the spinal canal. It is an involuntary reflex, not something the patient chooses to do.
This same principle of meningeal stretch underlies the related Kernig sign, in which the examiner extends the patient’s knee while the hip is flexed at ninety degrees, and pain or resistance to extension counts as positive. Both signs reflect the same underlying pathology, just provoked through different limb positions.
Origins of the Sign
Josef Brudzinski (1874–1917) was a Polish pediatrician who described the neck sign and argued it was present in a higher proportion of meningitis cases than the earlier Kernig sign.1JAMA Neurology. The Signs of Kernig and Brudzinski Brudzinski actually described several different signs of meningeal irritation over the course of his career, though the neck sign is by far the most widely known and taught. VladÃmir Kernig had published his own leg-based sign decades earlier, in 1882, and the two tests have been taught as a pair in medical schools ever since. Despite their historical prominence, neither sign underwent rigorous diagnostic accuracy testing until well into the late twentieth and early twenty-first centuries. When researchers finally put them to the test against confirmed cerebrospinal fluid analysis, the results were sobering.
Diagnostic Accuracy in Adults
The uncomfortable reality is that the Brudzinski sign misses most cases of meningitis. The sign’s sensitivity in adults, meaning how often it is positive when meningitis is actually present, is consistently low across studies. A pooled analysis of nine studies estimated an overall sensitivity of roughly 28%, with a high specificity around 89%.2PubMed Central. Sensitivity and specificity of meningeal signs in patients with meningitis In plain terms, a negative Brudzinski sign does not meaningfully reassure you that meningitis is absent, but a positive one does make the diagnosis more likely.
Some individual studies paint an even starker picture. One well-known prospective study of adults with suspected meningitis found the sensitivity of the Brudzinski sign to be as low as 5%, with a likelihood ratio for a positive result of just 0.97, meaning a positive test barely shifted the probability of disease at all.3Clinical Infectious Diseases. The Diagnostic Accuracy of Kernig’s Sign, Brudzinski’s Sign, and Nuchal Rigidity in Adults with Suspected Meningitis That same study found that even among patients with moderate cerebrospinal fluid inflammation, the sign’s accuracy did not improve meaningfully. Only in patients with very severe meningeal inflammation did a related sign, nuchal rigidity, begin to show reliable diagnostic value.
Another hospital-based study confirmed the pattern: none of the classic physical signs of meningeal irritation could accurately distinguish patients with meningitis from those without it. The Brudzinski sign produced a positive likelihood ratio of 1.69 with a wide confidence interval that crossed 1.0, meaning the result was not statistically reliable as a discriminator.4PubMed. Accuracy of physical signs for detecting meningitis: a hospital-based diagnostic accuracy study
These numbers do not mean the test is useless, but they do mean that clinicians cannot rely on it to rule meningitis in or out. A patient presenting with fever, headache, and an altered mental state needs a lumbar puncture regardless of whether the Brudzinski sign is positive or negative. The sign is one data point in a clinical picture, not a gate that decides whether further testing happens.
Performance in Children
Because Brudzinski himself was a pediatrician, you might expect the sign to work better in the population it was designed for. The picture is modestly better in children, but still far from reliable. One study of children with suspected bacterial meningitis found a sensitivity of about 53% and specificity of roughly 78% for the Brudzinski sign.5PubMed. The diagnostic accuracy of the ‘classic meningeal signs’ in children with suspected bacterial meningitis That means the sign was positive in just over half of children who actually had meningitis and was negative in about one in five children who did not. The researchers concluded that better bedside diagnostic approaches are needed.
A separate study looking at children found the Brudzinski sign present in about 51% of patients with confirmed meningitis, with a relatively high positive predictive value of 81%.6Pediatric Emergency Care. Diagnostic Accuracy of Clinical Symptoms and Signs in Children With Meningitis That positive predictive value is more encouraging: when the sign was present in a child, it usually did indicate meningitis. But the flip side is that half of the children with meningitis had a negative sign, so a normal exam still cannot rule it out.
In infants under about 12 to 18 months, the Brudzinski sign is even less dependable. Young infants with meningitis frequently present without the classic meningeal signs at all. Instead, they may show irritability, poor feeding, a bulging fontanelle, or simply look unwell without any specific localizing sign. Clinicians evaluating febrile infants with possible meningitis generally have a low threshold for lumbar puncture precisely because the physical exam is unreliable in this age group.
How It Compares to Other Bedside Tests
The Brudzinski sign is usually taught alongside several other bedside maneuvers for meningeal irritation, and a natural question is whether any of them perform better. The short answer is that none are great, and they have different trade-offs between sensitivity and specificity.
Nuchal rigidity, the simplest test where the examiner checks whether the patient resists passive neck flexion, tends to be more sensitive than the Brudzinski sign but less specific. The pooled analysis that estimated Brudzinski sensitivity at around 28% found nuchal rigidity sensitivity at roughly 46%, but its specificity dropped to about 71%.7PubMed Central. Sensitivity and specificity of meningeal signs in patients with meningitis So nuchal rigidity catches more true cases but also produces more false alarms.
The jolt accentuation of headache test, in which the patient rotates their head horizontally two to three times per second and reports whether headache worsens, was initially reported to have very high sensitivity for meningitis. Later studies were less enthusiastic. One study of adults found jolt accentuation had a sensitivity of just 21% for cerebrospinal fluid pleocytosis, barely better than the Brudzinski sign’s 2% in the same cohort, while nuchal rigidity came in at 13%.8The American Journal of Emergency Medicine. Jolt accentuation of headache and other clinical signs: poor predictors of meningitis in adults That same study described Brudzinski and Kernig as having moderate positive predictive value but essentially no ability to rule meningitis out when absent.
An Iranian emergency department study found the Brudzinski sign had an overall diagnostic accuracy of 0.72, which was slightly better than both nuchal rigidity at 0.68 and the Kernig sign at 0.67, with jolt accentuation of headache edging ahead at 0.75.9PubMed Central. Accuracy of Neck stiffness, Kernig, Brudzinski, and Jolt Accentuation of Headache Signs in Early Detection of Meningitis Once again, Kernig and Brudzinski had the highest specificity in the group. The pattern across studies is remarkably consistent: these classic signs are specific but insensitive. When they are present, they point toward meningitis. When they are absent, which is most of the time even in confirmed cases, they tell you very little.
Why the Sign Is So Often Absent in Confirmed Meningitis
If the mechanism makes such intuitive sense, why does the Brudzinski sign fail to show up in so many people who actually have inflamed meninges? Several factors contribute.
The degree of inflammation matters enormously. Viral meningitis, which accounts for most cases overall, often produces milder meningeal inflammation than bacterial meningitis. Patients with viral meningitis may feel miserable but never develop enough meningeal irritation to trigger the reflexive hip flexion. Even in bacterial meningitis, early in the course of illness the inflammation may not yet be severe enough to produce the classic signs. The one study that found diagnostic value for nuchal rigidity only saw it in patients with very severe inflammation, defined as more than 1,000 white blood cells per milliliter of cerebrospinal fluid.10Clinical Infectious Diseases. The Diagnostic Accuracy of Kernig’s Sign, Brudzinski’s Sign, and Nuchal Rigidity in Adults with Suspected Meningitis
Immunocompromised patients may mount a blunted inflammatory response, producing less meningeal swelling and therefore fewer physical signs even when a serious infection is present. Elderly patients are another notoriously tricky group: they often present with confusion or lethargy rather than the classic triad of fever, headache, and neck stiffness, and their meningeal signs are frequently absent or subtle. Patients who are already on anti-inflammatory medications or antibiotics before being examined may also have attenuated signs. And then there is simple variability in how people respond to the maneuver: body habitus, baseline flexibility, and the patient’s level of alertness and cooperation all influence whether the examiner can detect a positive sign.
Beyond Infections
While meningitis is the condition most associated with the Brudzinski sign, any process that irritates the meninges can theoretically produce it. Subarachnoid hemorrhage, in which blood leaks into the space surrounding the brain, is the most important non-infectious cause. Blood is a potent irritant to the meninges, and patients with subarachnoid hemorrhage commonly develop nuchal rigidity and may exhibit a positive Brudzinski or Kernig sign. In these patients, the sudden onset of a severe headache (often described as the worst of their life) is the key clinical feature, and meningeal signs develop over hours as the blood irritates the membranes.
Carcinomatous meningitis, where cancer cells spread to the meninges, can also produce meningeal signs, though these tend to develop more gradually. Certain chemical meningitides, caused by the introduction of irritating substances into the cerebrospinal fluid (sometimes as a complication of spinal procedures), can trigger the same findings. In all of these situations, the mechanism is the same: irritation and inflammation of the meninges leads to protective guarding and reflexive limb movement when the membranes are stretched.
The Other Brudzinski Signs
Most clinicians and students learn only the neck sign, but Brudzinski described several other maneuvers during his career. The cheek sign involves pressing on the cheek just below the zygomatic arch; a positive result is a reflexive flexion of the forearm and sometimes the arm. The symphysis sign involves pressing on the pubic symphysis, with a positive result being flexion and abduction of the legs. The contralateral leg sign, sometimes called Brudzinski’s reciprocal sign, is seen when passive flexion of one hip and knee causes the opposite leg to flex as well.
These lesser-known variants are rarely tested in clinical practice today and have almost no modern diagnostic accuracy data. They appear in neurology textbooks as historical curiosities more than practical tools. The neck sign endures in clinical teaching partly because it is the simplest to perform and the one that has been subjected to the most research, however disappointing that research has been.
When the Sign Still Changes Clinical Decisions
Given its poor sensitivity, you might wonder why anyone still checks for the Brudzinski sign at all. The answer lies in clinical context. In settings where lumbar puncture is not immediately available, or where a clinician is triaging a large number of patients with febrile illness, a positive Brudzinski sign can help prioritize who needs urgent evaluation. It does not replace cerebrospinal fluid analysis, but it can speed up the decision to pursue it.
In resource-limited settings, where laboratory testing may be delayed or unavailable, the combination of meningeal signs with clinical features like fever, headache, and altered consciousness takes on greater importance simply because there is no other tool. The sign’s high specificity means that when it is present, it meaningfully raises the probability of meningeal irritation and can justify empiric antibiotic treatment while awaiting confirmation.
In well-resourced emergency departments, the sign’s role is more modest. Current clinical guidelines generally recommend lumbar puncture for any patient with a strong clinical suspicion of meningitis, regardless of whether meningeal signs are present. The threshold for performing a lumbar puncture in an immunocompromised patient, an elderly patient with unexplained confusion, or a febrile infant is appropriately low and does not hinge on whether the Brudzinski sign is positive. In this context, the sign is best understood as a quick screen that might add a small piece of supporting evidence but should never be used as a reason to withhold further investigation.
Common Misunderstandings About Meningeal Signs
Perhaps the most widespread misconception is that a negative Brudzinski sign means meningitis is unlikely. The evidence is clear that this is not the case: roughly 70 to 95% of adults with confirmed meningitis will have a negative Brudzinski sign, depending on the study and the population.11PubMed Central. Sensitivity and specificity of meningeal signs in patients with meningitis Using a negative sign to reassure yourself that a patient does not have meningitis is dangerous and runs counter to what the data show.
Another misunderstanding is conflating Brudzinski and Kernig signs as though they are interchangeable. While both reflect meningeal irritation, they provoke the stretch through different mechanisms, and their diagnostic performance differs across studies. In children, Kernig’s sign tends to have a higher specificity than Brudzinski’s, while Brudzinski’s sign tends to be more sensitive.12PubMed. The diagnostic accuracy of the ‘classic meningeal signs’ in children with suspected bacterial meningitis Neither is sufficient on its own, and performing both adds only marginally to the clinical picture.
A subtler misunderstanding involves the difference between neck stiffness as reported by the patient and nuchal rigidity as detected by the examiner. A patient who says “my neck is stiff” might have anything from muscle tension to early meningeal irritation. Nuchal rigidity on examination, where the examiner feels resistance to passive flexion, is a distinct finding that carries more diagnostic weight, though as discussed, even its sensitivity is well under 50% in most studies. Patients sometimes assume that the absence of neck stiffness rules out serious illness, which it does not.
How Technique Affects Results
One underappreciated factor in the variability of reported accuracy is that different clinicians perform and interpret the test differently. There is no universally standardized protocol for how fast the neck should be flexed, how far it should go, or what degree of leg movement counts as positive. A vigorous, rapid flexion might provoke a pain-withdrawal response in anyone with neck discomfort, producing a false positive. A tentative, slow flexion might not stretch the meninges enough to trigger the reflex, producing a false negative. Some examiners count any knee movement as positive; others require obvious, clear hip and knee flexion.
This variability in technique helps explain why sensitivity estimates range from 2% to over 50% across different studies and populations. It also means that when a study reports a sensitivity of 5%, that number may partly reflect how strictly the investigators defined a positive test rather than some fixed biological truth about the sign. Standardizing the technique and the criteria for a positive result would likely tighten these estimates, but no widely adopted standardized protocol currently exists. Until one does, the Brudzinski sign remains a somewhat subjective clinical tool whose performance depends in part on who is performing it and how.