To report a rare case of adult-onset subacute sclerosing panencephalitis (SSPE) and investigate current diagnostic and treatment guidelines.

SSPE is a rare, progressive condition associated with significant morbidity and mortality caused by the measles virus.  SSPE primarily affects children and usually occurs at a median of 10 years after initial measles infection, but the latency period can vary from 1 month to 27 years. Adult onset SSPE is rare and has more than a 2:1 male predominance. There has been a steady decline in United States SSPE cases since the measles vaccine was introduced with only 4-5 cases reported per year.  However, this rate is often higher in developing countries and may increase in the United States with recent emerging vaccine hesitancy.

A 32-year-old female with no significant past medical history presented with subacute progressive painless vision loss and cognitive decline. An ophthalmologic exam revealed bilateral temporal predominant optic disc pallor, more severe in the right eye. Brain magnetic resonance imaging (MRI) revealed abnormal T2 hyperintensities of the right occipital and left parieto-occipital periventricular white matter with no post-contrast enhancement. A routine EEG showed nearly continuous left hemispheric focal slowing along with periodic delta complexes every 5-10 seconds raising concern for SSPE. A lumbar puncture was significant for greatly elevated measles rubeola antibody IgG, thus confirming the diagnosis of SSPE.  

This case highlights important diagnostic criteria and exam findings in SSPE. With the recent decrease in vaccination rates due to vaccine hesitancy, the incidence of this rare disease may increase in the coming years. Therefore, it is important to keep SSPE on the differential for patients presenting with confusion and vision loss.