A thorough history and physical examination are paramount to determining the diagnosis. Key questions must include prodromal events and associated signs and symptoms, such as fever, headache, weakness, vomiting, diarrhea, gait disturbances, head tilt, rash, palpitations, abdominal pain, hematuria, and weight loss. Inquiries also should be made regarding past medical history, family history, and immunization status. The examination should look for signs of occult infection, trauma, toxicity, or metabolic disease. A useful tool for organizing diagnostic possibilities is in the mnemonic AEIOU TIPS (Table 77-1).
Diagnostic adjuncts may include analysis of blood, gastric fluid, urine, stool, cerebrospinal fluid, electrocardiography, or selected radiographic studies, and should be guided by the clinical situation. Rapid bedside glucose determination is a universally accepted standard. If meningitis or encephalitis is suspected, lumbar puncture and cerebrospinal fluid analysis should be done as rapidly as possible after initial resuscitation and stabilization. A 12-lead electrocardiogram should be obtained in cases in which there are pathologic auscultatory findings or rhythm disturbances.