Walsh & Hoyt: Laboratory Studies

Many patients who develop EL, regardless of type, have normal cerebrospinal fluid (CSF). Others demonstrate mild mononuclear pleocytosis in the CSF associated with minimal increase in CSF protein concentration and, occasionally, a mild increase in glucose concentration. Oligoclonal bands of immunoglobulin (Ig) G are present in the CSF of some affected patients. Electroencephalography may show diffuse slowing, abnormal spikes, or other abnormalities. Neuroimaging studies generally are unrevealing, although several authors have reported abnormalities in the substantia nigra on MR imaging. Positron emission tomographic scanning showed an altered pattern of dopamine and glucose metabolism in a patient with acute sporadic EL unlike that seen in PD; however, PET scanning in another patient studied many years after the encephalitic episode showed changes similar to those in PD.