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ESSENTIALS OF DIAGNOSIS
Fever, headache, vomiting, delirium, convulsions.
Petechial rash on skin and mucous membranes in many.
Neck and back stiffness and positive Kernig and Brudzinski signs are characteristic.
Purulent spinal fluid with gram-negative intracellular and extracellular diplococci.
Culture of cerebrospinal fluid, blood, or petechial aspiration confirms the diagnosis.
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GENERAL CONSIDERATIONS
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Meningococcal meningitis is caused by Neisseria meningitidis of groups A, B, C, Y, and W-135, among others. Meningitis due to serogroup A is uncommon in the United States. Serogroup B generally causes sporadic cases. Serogroup C meningococcus is the most common cause of epidemic disease in the United States. Up to 40% of persons are nasopharyngeal carriers of meningococci, but disease develops in relatively few of these persons. Infection is transmitted by droplets. The clinical illness may take the form of meningococcemia (a fulminant form of septicemia without meningitis), meningococcemia with meningitis, or meningitis. Recurrent meningococcemia with fever, rash, and arthritis is seen rarely in patients with certain terminal complement deficiencies. Asplenic patients are also at risk.
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High fever, chills, nausea, vomiting, and headache as well as back, abdominal, and extremity pains are typical. Rapidly developing confusion, delirium, seizures, and coma occur in some. On examination, nuchal and back rigidity are typical. Positive Kernig and Brudzinski signs (Kernig sign is pain in the hamstrings upon extension of the knee with the hip at 90-degree flexion; Brudzinski sign is flexion of the knee in response to flexion of the neck) are specific but not sensitive findings. A petechial rash appearing in the lower extremities and at pressure points is found in most cases. Petechiae may vary in size from pinpoint lesions to large ecchymoses or even skin gangrene that may later slough.
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B. Laboratory Findings
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Lumbar puncture typically reveals a cloudy or purulent cerebrospinal fluid, with elevated pressure, increased protein, and decreased glucose content. The fluid usually contains greater than 1000 cells/mcL, with polymorphonuclear cells predominating and containing gram-negative intracellular diplococci. The absence of organisms in a Gram-stained smear of the cerebrospinal fluid sediment does not rule out the diagnosis. The capsular polysaccharide can be demonstrated in cerebrospinal fluid or urine by latex agglutination; this is useful in partially treated patients, though sensitivity is 60–80%. The organism is usually demonstrated by smear and culture of the cerebrospinal fluid, oropharynx, blood, or aspirated petechiae.
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Disseminated intravascular coagulation is an important complication of meningococcal infection and is typically present in toxic patients with ecchymotic skin lesions.
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DIFFERENTIAL DIAGNOSIS
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Meningococcal meningitis must be differentiated from other meningitides. In small infants and in older adults, fever or stiff neck is often missing, and altered mental status may dominate the picture.
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Rickettsial, echovirus, and, rarely, other bacterial infections (eg, staphylococcal infections, scarlet fever) also cause petechial rash.