|Normal||Bacterial Meningitis||Viral Meningitis||Fungal/TB|
|Opening Pressure (cm H2O)||< 15||↑↑||Normal/mild ↑||Variable|
|Protein (mg/dL)||15-45||↑||Normal/mild ↑||↑|
|WBC||0-8||↑↑ (>1000)||↑ (5-300)||↑|
|WBC differential||Even||>80% PMNs||>50% Lymphs, <20% PMNs||50-80% Lymphs|
|Gram Stain||Normal||60-90 % +||N/A||37-87% AFB +|
Differentiate between meningitis and encephalitis:
Brain function: abnormalities of brain function expected with encephalitis: AMS, motor/sensory deficits, speech/movement disorders
*distinction frequently blurred – meningioencephalitis both parenchymal and meningeal process.
Kernig Sign: inability/reluctance to allow full extension of the knee when hip is flexed at 90 degrees.
Brudzinski Sign: spontaneous flexion of the hip during attempted passive flexion of the neck.
*5% sensitivity and 95% specificity!
Characteristic MRI patterns for encephalitis:
- HSV – temporal distribution
- WNV – thalamic distribution
- MS – periventricular (Dawson’s fingers)
Mallaret’s Meningitis: >3 recurrent episodes of HSV2 meningitis