Review Question - QID 105829

This patient with a history of fevers and headaches that now presents with altered mental status and a purpuric rash likely has meningococcal meningitis. Analysis of cerebrospinal fluid (CSF) would most likely demonstrate gram-negative diplococci.

Meningitis may be due to bacterial, viral, or fungal pathogens. Fever, altered mental status, and positive Brudzinski's sign (flexion of the hips and knees in response to passive neck flexion) are typical signs and symptoms. Streptococcus pneumoniae and Neisseria meningitidis are common bacterial pathogens. In particular, Neisseria meningitidis is a more common cause of bacterial meningitis in younger people living in close quarters such as in college dormitories or military barracks. Disseminated intravascular coagulation is a common associated feature and often presents with a purpuric rash over the extremities, as in this patient. For patients in whom bacterial meningitis is suspected, the first step in management is the immediate administration of broad-spectrum antibiotics. Generally, guidelines recommend vancomycin, ceftriaxone, and acyclovir. For neonates or patients older than 50, ampicillin is often added to provide coverage of Listeria species. Corticosteroids are often administered with the first dose of antibiotics in order to prevent the development of neurologic deficits such as hearing loss. Brain imaging is generally performed prior to lumbar puncture to exclude a mass-occupying lesion due to the associated risk of herniation when performing lumbar puncture. Analysis of CSF typically demonstrates a neutrophilic pleocytosis, elevated protein, low glucose, and elevated opening pressure. Gram-staining of CSF will demonstrate gram-negative diplococci in those with meningococcal disease. Patients require admission to the intensive care unit with broad-spectrum antibiotics and supportive care.

Bamberger discusses the evaluation and management of meningitis. Empiric antibiotic therapy for bacterial meningitis should not be delayed to obtain head imaging or multiple attempts at a lumbar puncture. Initiating dexamethasone with antibiotics has been shown to improve morbidity and mortality in patients suffering from S. pneumoniae meningitis.

Cunha reviews laboratory values that can be useful in diagnosing acute bacterial meningitis. CSF Gram stain and elevated lactic acid levels are the most rapid and reliable ways to confirm the diagnosis of acute bacterial meningitis. Normal CSF lactic acid levels can rule out bacterial meningitis and may re-direct diagnosis towards encephalitis or viral meningitis.

Figure A demonstrates a purpuric rash over the lower extremities consistent with disseminated intravascular coagulation. The rash typically begins with petechiae that coalesce into purpuric lesions. Note the dark purple appearance and distribution of the rash.

Illustration A details expected findings on CSF analysis by associated pathogen. Note the differences in findings that distinguish viral, bacterial, and tuberculous meningitis.

Incorrect Answers:
Answer 1: Elevated glucose would be unlikely. Patients with viral meningitis may have a normal or slightly elevated CSF glucose. However, this patient's presentation is more suggestive of bacterial meningitis.

Answer 3: Gram-positive lancet-shaped diplococci would be expected in patients with meningitis due to Streptococcus pneumoniae. However, this patient's presentation is more suggestive of Meningococcal meningitis.

Answer 4: Low CSF opening pressure would be unusual. Bacterial meningitis causes an intense CNS inflammatory response that results in elevated intracranial pressure and therefore an elevated CSF opening pressure.

Answer 5: Lymphocytic pleocytosis would be expected in a patient with viral meningitis. However, this patient's presentation is more suggestive of bacterial meningitis.

Bullet Summary:
Cerebrospinal fluid analysis in patients with meningococcal meningitis will demonstrate gram-negative diplococci.