Abstracts

Rationale: Subacute sclerosing panencephalitis (SSPE) is a chronic progressive neurodegenerative illness caused by wild-type measles virus infection of the central nervous system. It may mimic autoimmune or infectious encephalitis in its initial presentation, and diagnosis is difficult. This case underscores the challenges in diagnosis of SSPE and the importance of its inclusion in the differential diagnosis for encephalopathy and myoclonus in children who are underimmunized or may have been exposed to measles prior to vaccination.

Methods: Electronic medical records were reviewed, including progress notes, labs, MRI reports and images, and EEG reports and tracings.

Results: A 9-year-old child, who had recently immigrated from a measles-endemic region, presented with acute confusion, behavioral changes, ataxia, and myoclonic seizures. Initial neurological examination revealed lethargy, delayed responses, a right Babinski sign, and right lower extremity weakness. Routine labs, metabolic and infectious panels, and brain/spine MRI/MRA were unremarkable. CSF analysis showed mild pleocytosis and elevated IgG index. Extensive testing for infectious, demyelinating, and autoimmune causes—including evaluation for autoimmune encephalitis—was negative. The family reported that the child had received routine childhood vaccinations including measles, but no documentation of immunization status was available. There was no history of a characteristic measles rash. Given the initial working diagnosis of seronegative autoimmune or post-infectious encephalitis, the patient received corticosteroids, IVIG, and plasmapheresis. However, there was minimal neurological improvement. By hospital day 12, he exhibited only minimal withdrawal to painful stimuli. Repeat EEG showed global background slowing with periodic discharges every 3–5 seconds, raising suspicion for subacute sclerosing panencephalitis. On hospital day 20, CSF studies obtained on day 2 returned with markedly elevated measles IgG antibody titers ( >300 AU/mL), confirming the diagnosis of SSPE. Following confirmation of the diagnosis, immunotherapy was discontinued, and multidisciplinary teams including Neurology, Infectious Disease, and Palliative Care were involved for prognostic counseling and supportive planning. The patient was discharged home and later traveled abroad for continued care.

Conclusions: This case emphasizes the need for early consideration of SSPE in children who present with progressive encephalopathy and myoclonus, especially those who have uncertain immunization status or have spent time in endemic areas prior to vaccination. Early CSF measles antibody testing and typical EEG patterns can help in early diagnosis. While SSPE lacks a definitive cure, early diagnosis is necessary to initiate supportive therapy, avoid unnecessary treatment and minimize the risk of iatrogenic adverse events, and to provide appropriate counseling for the families.

Funding: No external funding was received for this work.