Meningitis is inflammation of the membranes (dura, pia mater, and arachnoid) surrounding the brain and spinal cord. Bacterial meningitis most commonly results from seeding of the leptomeninges from a distant focus (hematogenous spread). It can also result from a direct extension from a contiguous focus (eg, sinusitis, otitis media, mastoiditis) or by direct invasion (eg, head trauma). Etiologies in the neonatal period include Group B streptococci, gram-negative enteric bacilli (Escherichia coli, Enterobacter spp.), and Listeria monocytogenes. Etiology from age 1 to 3 months includes Streptococcus pneumoniae, Neisseria meningitides, Haemophilus influenzae type b (Hib), and L monocytogenes. Etiology in infants >3 months include S pneumoniae, N meningitides, and Hib (unvaccinated children). In patients with ventriculoperitoneal shunts, coagulase-negative Staphylococcus epidermidis and Staphylococcus aureus are the pathogens. Tuberculous meningitis may present with a gradual onset over several weeks. Low-grade fever, weight loss, adenopathy, vomiting, lethargy, cranial nerve palsies, and coma are common presentations. Differential diagnosis includes other types of meningitis, subarachnoid hemorrhage (ruptured arteriovenous malformation [AVM]/aneurysm), parameningeal/paraspinal infection (eg, brain abscess, subdural or epidural abscess), retropharyngeal abscess, and trauma (eg, shaken impact syndrome, subdural or epidural hematoma).
Emergency Department Treatment and Disposition
Stabilize the patient and provide continuous cardiac and pulse oximetry monitoring, and fluid resuscitation with crystalloids for septic shock. If patient is not in shock, restrict intravenous (IV) fluid to basal requirement with 0.33% NaCl solution because of possible syndrome of inappropriate antidiuretic hormone (SIADH). Obtain cerebrospinal fluid (CSF) with lumbar puncture (LP). Head CT scan is not required routinely before LP when there is a clinical diagnosis of uncomplicated meningitis. If focal neurologic signs are present (eg, suspected complications like subdural effusion or empyema) or there is papilledema, begin antibiotics and obtain a CT scan before performing LP. Antigen detection tests (eg, latex agglutination) may help in partially treated meningitis. Order India ink stain for immunocompromised patients, and acid-fast stain when tuberculous meningitis is suspected. Order complete blood count, blood culture, serum electrolytes (monitoring for SIADH), glucose, and coagulation profile (disseminated intravascular coagulation). Place a 5–tuberculin unit purified protein derivative tuberculin test on the forearm of all patients with meningitis in areas where tuberculosis is endemic. Treat patients <4 weeks of age empirically with ampicillin and cefotaxime or ampicillin and an aminoglycoside (eg, gentamicin). Consider antiviral therapy if herpes is suspected. Treat patients >4 weeks of age empirically with vancomycin and cefotaxime or ceftriaxone. Offer antibiotic prophylaxis to close contacts for exposure to Hib and N meningitides. Dexamethasone (if given before or concurrently with the first dose of antibiotics) may help decrease hearing loss associated with Hib meningitis. Admit patients with a clinical diagnosis; admit those with septic shock requiring resuscitation to the ICU. Use standard and droplet precautions for the first 24 hours after institution of appropriate antibiotics.
Figure 13.1 ▪ Bacterial Meningitis Presenting with Purpura.