Stage I is characterized by subtle behavioral changes, cognitive decline, emotional lability, lethargy, and nonspecific neurologic symptoms. This stage may last for weeks to months. This stage may last three months or less. Features of Stage IV include active startle reflex, flexor limb positioning, and wandering eye movements. At this time, myoclonus, seizures, and rigidity are less frequent than in prior stages.
Death occurs in Stage IV, often the result of intercurrent illnesses such as pneumonia.
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.