Chapter 20-13: Meningitis

TEXTBOOK PRESENTATION

Classically, meningitis presents with the acute onset of the triad of headache, fever, and a stiff neck. Meningitis may occur in the setting of a cluster of cases.

DISEASE HIGHLIGHTS

1. The presentation of fever and headache is common and can be worrisome, potentially caused by anything from influenza to meningitis. The differential includes:

   1. Viral infections and almost any other febrile illness

   2. Meningitis (bacterial, fungal, viral, or parasitic)

   3. Encephalitis

   4. Sinusitis

   5. CNS abscess

   6. Septic cavernous sinus thrombosis

2. Although certainly not the most common cause of fever and headache, meningitis is a relatively common, potentially life-threatening illness.

3. Viral causes are 3–4 times more common than bacterial causes and have a generally favorable prognosis.

4. Bacterial meningitis must be treated as a medical emergency.

5. Community-acquired bacterial meningitis has a mortality rate of about 25%. Mortality rates vary by organism.

6. Mortality rates are higher for hospital-acquired infections.

7. The most common organisms are listed in Table 20-9.

EVIDENCE-BASED DIAGNOSIS

1. A review studied patients in Holland in whom community-­acquired bacterial meningitis was diagnosed over a 3 1/2 year time period; the prevalence of various exam features follow:

   1. 95% of patients had at least 2 of the findings of headache, fever, stiff neck, or mental status changes

      1. 87% had a headache

      2. 83% had stiff neck

      3. 77% had temperature > 38.0°C

      4. 69% had a change in mental status

   2. 33% had focal neurologic findings

   3. 34% of those who had imaging done had an abnormal CT scan

2. Patients with suppressed immune systems and the elderly are less likely to have a stiff neck.

   1. Two of the most commonly used meningeal signs are Kernig (the inability to extend the knee with a flexed hip) and Brudzinski (the demonstration of flexion of both the knees and hips upon forced flexion of the neck).

   2. These signs are present in only about 60% of patients with meningitis.

3. Lumbar puncture

   1. Lumbar puncture is the only means of making a definitive diagnosis.

   2. The CSF in acute bacterial meningitis will demonstrate WBCs with neutrophil predominance, low glucose, and high protein.

4. Patients with contraindications to lumbar puncture

   1. Frequently, the question of contraindication to lumbar puncture is raised.

   2. Performing a ...