Laboratory findings reveal increased serum and CSF rubeola IgG titers with normal IgM titers. Early in the course of the disease these periodic discharges may occur on a normal background but later the background becomes increasingly slower and disrupted. During an acute rubeola infection, the virus and infected cells are quickly recognized and cleared from the body by the immune system. Several theories exist as to why rubeola persists as a latent infection in the CNS in some patients. Other features seen include Cowdry A nuclear inclusions and symmetric demyelination progressing in an occipital to frontal pattern.
Viral antigen localizes immunogistochemical to dendrites and axons.
Neurofibrillary tanges are seen late in symptomatic patients. Some patients' symptoms stabilize in Stage III for up to 2 years. Nonetheless, almost all patients die within 10 years of the initial symptoms. The incidence of SSPE varies throughout the world. Regional disparity is most likely due to variable early childhood rubeola immunization.