Brudzinski sign

**Definition / Technique:** With the patient supine, the examiner passively flexes the neck (chin toward chest). A positive sign is involuntary flexion of the hips and knees. This is the "nuchal" or neck Brudzinski sign. A related "contralateral leg sign" occurs when passive flexion of one hip and knee causes reflex flexion of the opposite leg.

**Pathophysiology:** Inflammation of the meninges (or blood in the subarachnoid space) makes stretching of the inflamed meninges, nerve roots, and spinal cord painful. Neck flexion tractions on these structures. The patient reflexively flexes the hips and knees to relieve the tension.

**Clinical significance:** - Classic meningitis triad: fever, headache, and nuchal rigidity (neck stiffness). Altered mental status is also common, and the 4 features together are often cited as the "classic tetrad." - Meningeal signs include Brudzinski sign, Kernig sign (pain or resistance to passive knee extension with the hip flexed at 90°), and nuchal rigidity. - Sensitivity is low (~5–10%) and specificity is high (~95%+). Absence of the sign does NOT rule out meningitis. Neonates, infants, elderly, and immunocompromised patients often lack meningeal signs. - Also seen in subarachnoid hemorrhage ("worst headache of my life"), carcinomatous or chemical meningitis, and some cases of posterior fossa pathology.

**Key associations / Workup:** - Common pathogens: *Streptococcus pneumoniae* and *Neisseria meningitidis* in adults. Add *Listeria monocytogenes* in neonates, those >50 yr, and immunocompromised patients. *Group B Streptococcus* and *E. coli* are common in neonates. Viral (enterovirus) meningitis is the most common cause overall and is milder. - Diagnosis: lumbar puncture (CSF analysis). Bacterial meningitis shows ↑ neutrophils, ↑ protein, ↓ glucose, and ↑ opening pressure. Viral shows ↑ lymphocytes, normal glucose, and mildly ↑ protein. - Obtain CT head before LP if there are focal neurologic deficits, papilledema, altered mental status, seizure, or immunocompromise. Do not delay empiric antibiotics (and dexamethasone) for imaging. - Empiric treatment: ceftriaxone + vancomycin (add ampicillin if risk for Listeria). Give dexamethasone before or with the first antibiotic dose for suspected pneumococcal meningitis. - Prophylaxis for close contacts of *N. meningitidis*: rifampin, ciprofloxacin, or ceftriaxone.

**Board pearls:** - Brudzinski = neck flexion → hip and knee flexion. Kernig = knee extension painful with hip flexed. - Both are signs of meningeal irritation and are not specific to infection. - Named for Polish pediatrician Józef Brudziński (1909).