Review of systems seeks symptoms that suggest possible causes: Vomiting, diarrhea, or both: Dehydration, electrolyte disturbance Palpitations: Hyperthyroidism, drug effects including withdrawal Polyuria and polydipsia: Diabetes mellitus Tremors: Parkinson disease, withdrawal syndromes Difficulty walking or speaking: Multiple sclerosis, Parkinson disease, stroke Headache: Central nervous system (CNS) infection, complex migraine, hemorrhage, mass lesion Fever, cough, dysuria, vomiting, or diarrhea: Systemic infection Weight loss: Infection, cancer, inflammatory bowel disease, hyperthyroidism Paresthesias and weakness: Vitamin deficiency, stroke, demyelinating disease Relapsing and remitting neurologic symptoms: Multiple sclerosis, vasculitis Past medical history should identify known physical disorders that can cause mental symptoms (eg, thyroid, liver, or kidney disease; diabetes; HIV or COVID-19 infection).