In acute epidemic encephalitis the characteristic anatomic changes are perivascular iufiltrations, a moderate amount of neuronophagia, a mild degree of glia proliferation and occasionally hemorrhagic foci. These changes are most commonly found in the region of the midbrain and basal ganglions; more rarely other parts of the central nervous system are involved.
But these changes do not exhaust the histopathology of acute epidemic encephalitis. The material studied by the earlier workers was limited to that form of the disease often fatal in its early stage; as material becomes available from cases that have run a more or less protracted course, new findings may be expected.
Economo1 has reported a case which he called "chronic intermittently progressive lethargic encephalitis." His patient, 45 years of age, insidiously developed atypical lethargic encephalitis, characterized by alternate episodes of delirium and lethargy, dysarthria and the Babinski reflex with no ocular or other palsies or
GLOBUS JH, STRAUSS I. SUBACUTE EPIDEMIC (LETHARGIC) ENCEPHALITIS. Arch NeurPsych. 1922;8(2):122-138. doi:10.1001/archneurpsyc.1922.02190140013002