Sinai EM Journal Club

Emergency Medicine Discussion Forum

Usefulness of Kernig and Brudzinski Signs in Diagnosing Meningitis

Ah, the first Conference of the academic year. The new faces, with their bubbling enthisasm, suddenly confronted with the annual reading of the policies & procedures manual… why, it’s enough to give anyone a headache and photophobia. Which is why it’s so timely that we review meningitis, with a focus on some physical exam skills that can (but may not) help guide your diagnosis.

Tim reviewed a paper by Thomas et al out of Yale, published in Clinical Infectious Diseases (2002;Vol 35 July 1, pp46-52) called “The Diagnostic Accuracy of Kernig’s Sign, Bruzinski’s Sign, and Nuchal Rigidity in Adults with Suspected Meningitis.” Here’s his CAT sheet.

The researchers looked at anyone over 16 who presented to Yale-New Haven with “clinically suspected meningitis” (which they define as headache, fever, stiff neck, photophobia, nausea + vomiting) who were tapped. This was part of a larger cohort used in other studies. 301 were enrolled, 297 were tapped (four had CT’s that showed mass effect).

Physicians (28% interns, 55% residents, and 17% attendings) were required to document their history and exam findings before LP, but were NOT instructed on how to properly test Kernig’s and Brudzinski’s signs. Meningitis was considered to be present if the WBC count from the CSF was greater than 6 (regardless, as Scott and Ted pointed out, of whether the tap was traumatic or not).

Kernig’s sign (pain upon thigh flexion and knee extension) was shown to have a sensitivity of 5%, specificity of 95%, with a PPV of 27%, and NPV of 72%. Brudzinsky’s sign (flex the neck, see if the patient flexes thighs and knees in response) fared pretty much the same. Nuchal rigidity was 30% sensitive, 68% specific, with a PPV of 26% and NPV of 73%.

The group helpfully calculated likelihood ratios – but they were all around 1.0 (some subsets were higher, if they looked at severe meningeal inflammation, for example). An LR of around 1 means the pre-test probability is unaffected – your patient is just as likely to have the disease before you apply the test, as after. In other words, it’s useless. Furthermore, the sensitivities of Kernig’s and Brudzinski’s signs are poor – especially when you’re looking for a justification to tap (beyond, you know, your keen clinical suspicion). Also, these NPV’s are not good enough – we want a really high negative predictive value, because meningitis has such high mortality.

As we critically reviewed this paper (based on the format for evaluating diagnostic studies, see Jaeschke et al in JAMA 271(5):389-391 (Feb 2, 1994) and 271(9):703-707 (March 2, 1994) ) a few good points were made:

K+B’s oringal tests, 100 years ago, were based on a different population – one with mostly TB meningitis. Maybe that’s why they got 70% sensitivity. (Or, maybe they just knew how to do the test better than the Yale residents).

Ted pointed out something important: their criteria for meningitis was looser than our own: a WBC > 6 is meaningless in the presence of a traumatic tap, yet their methods don’t mention this possibility (maybe the Yale residents are really skilled?)

As for applicability, well Kerning’s and Brudzinski’s signs are benign tests, true, but this study suggests they don’t seem to be that useful. They don’t change the pretest probabilities of meningitis. Dr. Bais noted, wisely, this means we ought to study the signs properly applied – all Thomas’ paper shows is the signs aren’t useful as currently applied by Yalies.

An altogether more balanced approach to history and physical exam for meningitis was presented in Attia’s review, “Does This Adult Patient Have Acute Meningitis?” – part of JAMA’s rational clinical examination series (JAMA 281(2) ,175-181 July 14, 1999). This paper is chock full of useful tidbits (incidence is 3-11 per 100,000 person-years, 17% mortality in adults in the 80’s, even with therapy, 18% of survivors enduring longterm neuro deficits).

Their review of the literature shows that history alone cannot provide enough info for an accurate diagnosis of meningitis, but some aspects of physical exam could be useful: of the classic triad of fever, neck stiffness, and headache / altered MS, 95% of meningitis patients had at least 2 symptoms, and 99%-100% had at least one. Fever is the single most sensitie finding. Best yet, they report that jolt accentuation of headache has a sensitivity of 100% (who wouldn’t mind that maneuver?) and positive likelihood ratio of 2.2 for meningitis.

So, take home points from these papers? Fever, with headache (or changed MS) should prompt a meningitis workup, but no eponymous maneuvers should change your decision-making.

 

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July 10, 2006 - Posted by | Meningitis, Physical Exam

5 Comments »

  1. One big prolem with testing aspects of the clinical exam is the lack of standardization. This study didn’t even try to define the signs in question, but the problem goes beyond that. There are docs who are good at the physical exam and those who are less so. Given that physical exam skills are in decline, the number of the latter group probably grows each year. Each time you attempt to “test” some aspect of the physical exam, the “weak examiners” are likely to wash out the “skilled examiner” minority. Many clinical signs will appear to have no signiciance, but in fact it may be that most clinicians can’t realiably tell when the signs are there.

    It’s as if you had a lab test but instead of one centralized lab with quality control you have everyone performing the test in their basement with home equipment. Some folks may do it right; many will mess it up. If we did things that way most lab tests would appear to useless when tested as “evidence-based medicine”.

    While I am happy that I now have a justification to stop pulling people’s hamstrings, I’m not prepared to throw out the utility of the physical exam in meningitis entirely just yet.

    Comment by Denny | July 21, 2006 | Reply

  2. The question regarding how well interns and residents do their physical exam is an important one, and I disagree with the sentiment that this “represents reality.” The important question is whether it is even worth teaching medical students how to do these maneuvers accurately. A number of “procedural” type of studies has the same person trained in the maneuver do it to every patient in the study. Such a study would also accurately describe how the K and B maneuvers were defined (including degree rise, etc). In short, this kind of study really needs a more laboratory setting.

    It may take a while, but a single person could collect his data over a few years and be quickly be able to tell us at least if the sensitivity is greater than 5%.

    Comment by davidkpark | July 22, 2006 | Reply

  3. Interesting Comments. Dave, what you are alluding to is the difference between efficacy studies and effectiveness studies. Efficacy examines a test in idealized conditions: well-trained staff, available equipment, motivated participants. Effectiveness studies try to look at how a test fares in the real world, where folks don’t often do things perfectly or consistently. Both of these study types are important. If you create a new diagnostic maneuver that has excellent parameters, but nobody except you can perform it well, then this is a flaw in the diagnostic test. A good diagnostic test is reproducible by folks without any extensive training. As to this study representing reality, you just have to ask yourself if you think your resident cohorts have a better or worse grasp of performing the two maneuvers; if you think our resident group is probably pretty close to Yale’s, then it represents reality.

    In regards to Matt’s comments, this study does not throw out the maneuvers, but it is not b/c of the poor physical dx skills of the participants. It is b/c part of the entry criteria for enrollment was neck stiffness, so the specificities will be falsely high. They included patients with viral meningitis, who often present with a mild course a little demonstrable meningeal irritation, this leads to falsely low sensitivities (when compared to the sensitivities for just a cohort of patients who are truly sick; these patients go on to grow evil bacteria or seemingly in the old days, tuberculosis). Physical exam tests of meningitis are affected by spectrum bias. The test gains sensitivity in the sicker patients.

    That being said, it is important to understand that even despite the above, the performance of kernigs or bruds probably does not add anything to the findings of neck stiffness or meningeal irritation. Performing a test that does not help you change your pretest probability is a bad move.

    Nick–you may want to consider avoiding the reporting of NPV and PPV entirely. They are very misleading parameters and authors only use them b/c they often make write-ups sound much more impressive. Likelihood ratios give far more information and are not skewed by the prevalence of disease in the original study.

    Comment by weings01 | July 22, 2006 | Reply

  4. Could you post/upload some pictures about the special tests mentioned (Kernig’s & Brudzinski) on this page so that we could be get excessed to it.

    Thankyou

    Comment by Sieland Banda | August 11, 2009 | Reply

  5. Wonderful blog! Do you have any helpful hints for aspiring writers?
    I’m planning to start my own blog soon but I’m a little lost on everything.

    Would you suggest starting with a free platform like WordPress or
    go for a paid option? There are so many options out there that I’m completely overwhelmed .. Any suggestions? Many thanks!

    Comment by 2011 american music awards performances | October 22, 2012 | Reply


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