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NEUROLOGY*

*The authors acknowledge the special contributions of Binita R. Shah, MD, to prior edition.

BACTERIAL MENINGITIS

Clinical Summary

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), direct extension from 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. Etiologies from age 1 to 3 months include group B Streptococcus, gram-negative bacilli, Streptococcus pneumoniae, and Neisseria meningitides. Etiologies in infants >3 months include S pneumoniae, N meningitidis, group B Streptococcus, gram-negative bacilli, and Haemophilus influenzae type b (Hib; unvaccinated children).

In patients with ventriculoperitoneal (VP) shunts, coagulase-negative Staphylococcus epidermidis and Staphylococcus aureus are common pathogens. Tuberculous meningitis presents with a gradual onset (several weeks). Low-grade fever, weight loss, adenopathy, vomiting, lethargy, cranial nerve palsies, and coma are common presentations. Differential diagnosis includes viral meningitis, subarachnoid hemorrhage (ruptured arteriovenous malformation/aneurysm), parameningeal/paraspinal infection (eg, brain abscess, subdural or epidural abscess), retropharyngeal abscess, and trauma (eg, abusive head trauma, subdural or epidural hematoma).

FIGURE 13.1

Bacterial Meningitis Presenting with Purpura. An adolescent patient with AIDS presented with high fever, neck stiffness, and signs of septic shock with purpuric lesions (photograph taken on second day of hospitalization). Both blood and CSF cultures were positive for S pneumoniae. (Photo contributor: Binita R. Shah, MD.)

FIGURE 13.2

Bulging Anterior Fontanelle as a Presenting Sign of Meningitis. The anterior fontanelle is normally open in infants (usually closes between 9 and 18 months) and is pulsatile and slightly depressed in an infant in an upright position. The anterior fontanelle may appear full in an infant lying in a supine position or during crying. A bulging anterior fontanelle suggests increased intracranial pressure from any etiology (eg, meningitis, tumor, hydrocephalus). (Photo contributor: Binita R. Shah, MD.)

Emergency Department Treatment and Disposition

Stabilization of the patient and continuous cardiopulmonary monitoring are encouraged. Shock should be identified and addressed appropriately and expeditiously. Patients not in shock should receive IV fluid at maintenance with 0.9% NaCl solution because of possible syndrome of inappropriate antidiuretic hormone. Diagnosis is made with evaluation of CSF with lumbar puncture (LP). Head CT scan is not required routinely before LP when there is a clinical diagnosis of uncomplicated meningitis or no signs or symptoms of increased intracranial pressure (ICP). If focal neurologic signs are ...

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