Bacterial meningitis affects more than 1 million people per year globally and ranks as one of the top ten most deadly infectious diseases. Bacterial meningitis has a high frequency of neurologic sequelae and mortality and is treatable with antibiotics, which makes the diagnosis extremely important and time-sensitive. As compared with other febrile illnesses, bacterial meningitis is relatively rare. Because of this, many clinical tests have been described to help providers differentiate meningitis from other causes of fever and headache. Two of the most commonly used are Kernig's and Brudzinski's signs. The original report of Brudzinski's sign was in the late 1800s by Dr. Josef Brudzinski. At that time, he described four maneuvers to aid in the clinical diagnosis of meningitis. The four maneuvers he described included the Brudzinski's reflex, the cheek sign, the nape of the neck sign and the symphyseal sign. The most popular of the maneuvers is the nape of the neck sign, currently known as Brudzinski's sign.
Brudzinski's sign is characterized by reflexive flexion of the knees and hips following passive neck flexion. To elicit this sign, the examiner places one hand on the patient's chest and the other hand behind the patient's neck. The examiner then passively flexes the neck forward and assesses whether the knees and hips flex. Upon passive neck flexion, a positive test results when the patient flexes his knees and hips. During the process of performing the test, the hand on the chest prevents the patient from reflexively lifting his chest off the bed which decreases the specificity of the test. While the pathophysiology for the hip/knee flexion is not completely understood, the theory is that hip and knee flexion occurs as an involuntary reflex to compensate and help reduce meningeal irritation. Passive neck flexion causes spinal cord movement and stretching of the meninges, resulting in pain for patients with meningitis. The thinking is that the involuntary hip/knee flexion occurs to create maximal relaxation of the meninges, reducing pain.
While Brudzinski's sign is commonly used to assess for meningitis, it has limitations in the diagnosis of meningitis. Brudzinski's sign has low sensitivity but high specificity for detecting meningitis. For Brudzinski's sign, estimates are that the diagnostic sensitivity is between 2 and 43%, and the specificity for meningitis is between 80 to 100%. Given the low sensitivity of the test, the absence of Brudzinski's sign does little to rule out the diagnosis of meningitis and further testing is often necessary.
An additional limitation of Brudzinski's sign is the fact the sign is not useful in certain populations. In very young (less than 2 months), immunocompromised and elderly patients, Brudzinski's sign may be absent despite severe disease. Brudzinski's sign may be unreliable in these populations due to the presence of an open fontanelle or weakened immune response.
Meningitis is a devastating disease that without early treatment can cause lifelong neurologic sequelae or even death. Clinical signs and symptoms to aid in the early diagnosis and initiation of therapy are extremely important to help reduce long-term complications. While Brudzinski's sign may not definitively rule out meningitis, it can increase clinical suspicion of meningitis and trigger early treatment. Given its high specificity for the disease, there is a high likelihood of meningitis if the Brudzinski's sign is present. A positive result can aid providers who have a clinical suspicion of meningitis by allowing them to initiate antibiotics early. However, it is important to note that the absence of the sign does not rule out meningitis due to its poor sensitivity.
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