33-12: Meningococcal Meningitis

GENERAL CONSIDERATIONS

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.

CLINICAL FINDINGS

A. Symptoms and Signs

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 all over the body, including on mucous membranes, on 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.

B. Laboratory Findings

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 (1.0 × 10⁹/L) with polymorphonuclear cells predominating and containing gram-negative intracellular diplococci. The organism is usually demonstrated by smear and culture of the cerebrospinal fluid, oropharynx, blood, or aspirated petechiae. 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%.

Disseminated intravascular coagulation is an important complication of meningococcal infection and is typically present in toxic patients with ecchymotic skin lesions.

DIFFERENTIAL DIAGNOSIS

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.