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International Parkinson and Movement Disorder Society

        VOLUME 29, ISSUE 4 • DECEMBER 2025. 

2025 Movement Disorders Clinical Practice Review of The Year
The looming threat of subacute sclerosing panencephalitis: A call for action

Measles, caused by the Morbillivirus measles virus (MeV), is currently increasing globally, with significant surges observed in 2024-2025 across several regions, including the US, Europe, Canada and Mexico.1 Subacute sclerosing panencephalitis (SSPE) is one of the most devastating long-term complications of measles, which develops after an average latency of 7-10 years post-measles. Although spontaneous remission rates of up to 6% have been reported, SSPE is usually inexorably progressive and ultimately fatal. Gaps in vaccination coverage have not only fuelled measles outbreaks, but also risk a delayed wave of SSPE cases in the coming years. SSPE arises from persistence of mutated MeV in the brain, leading to neuronal injury and inflammation.  

SSPE affects children and adolescents, although adult-onset cases are increasingly recognized. It is characterized by a distinct clinical conglomeration of progressive neurobehavioral disturbances, vision loss, seizures, and movement disorders. Diagnosis relies on a combination of clinical and laboratory criteria.2,3 Particularly useful in the diagnosis is the presence of typical large voltage, long-interval, generalized periodic complexes on the electroencephalography, called Radermecker discharges, as well as elevated serum and cerebrospinal fluid anti-measles antibody titers. The course is usually relentlessly progressing, culminating in death. At present, no curative therapy exists, and treatment hinges on symptom-directed therapy combined with antiviral and/or immunomodulatory therapy, which are largely ineffective in curbing disease progression.4 A recent review published in Movement Disorders Clinical Practice (MDCP) journal and awarded the “2025 Review Article of the Year” in MDCP described the key features, pathophysiology, treatment and outcomes of movement disorders in SSPE.5 The work, conducted under the aegis of the MDS Infection-Related Movement Disorders Study Group, aimed to increase awareness and enhance early recognition of SSPE among movement disorder specialists. 

Movement disorders are observed in a significant proportion of patients with SSPE, ranging from 1.6-56% of patients. Interestingly, movement disorders may arise in any disease stage and occasionally be the presenting feature. These comprise ataxia, hyperkinetic (myoclonus, dystonia, chorea, tics, stereotypies, repetitive behaviors, eye movement abnormalities) and hypokinetic (parkinsonism, akinetic-rigid states) movement disorders. The temporal evolution of these motor manifestations tends to parallel disease progression, with ataxia, chorea, and dystonia dominating early phases, and parkinsonism emerging later, eventually culminating in a preterminal akinetic-rigid state.  

The most distinct abnormal movement, considered the motor signature of SSPE, is myoclonus. Myoclonus, observed in 84-92% of patients, has a peculiar phenomenology, characterized by a fast initial phase followed by a slow relaxation. Due to its distinctive features, descriptors such as ‘dystonic’ myoclonus, ‘hung-up’ myoclonus, and pseudomyoclonus have been used. Indeed, the source generator of myoclonus in SSPE remains a matter of debate, with epileptologists arguing in favor of a cortical epileptic origin (buttressed by its time-locked nature with EEG discharges and frequent response to anti-myoclonus antiseizure drugs) and movement disorder specialists favoring a subcortical origin due to its slow relaxing end-phase. Another common movement disorder is dystonia, which can progress into status dystonicus. Despite the well-characterized clinical features, radiological correlates remain elusive, with conventional MRI typically showing no distinct movement disorder–specific lesions. 

Fortunately, SSPE is a vaccine-preventable infection. The World Health Organization (WHO) advocates two doses of childhood measles vaccine for measles prevention, as single dose may not confer lifelong immunity.6 The relationship between vaccination and direct effects on decline in measles and consequent SSPE is epidemiologically well-established.7  

The current global resurgence of measles is thus a call to reinvigorate vaccination efforts and, simultaneously, to strengthen research into disease-modifying therapies for SSPE. For movement disorder specialists, vigilance is crucial, not only for early recognition and symptomatic management but also for contributing to interdisciplinary advocacy for prevention. 

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References 

  1. CDC. Measles Cases and Outbreaks. Measles (Rubeola). November 5, 2025. Accessed November 9, 2025. https://www.cdc.gov/measles/data-research/index.html 
  2. Jafri SK, Kumar R, Ibrahim SH. Subacute sclerosing panencephalitis – current perspectives. Pediatric Health Med Ther. 2018;9:67-71. doi:10.2147/PHMT.S126293 
  3. Dyken PR. Subacute sclerosing panencephalitis. Current status. Neurol Clin. 1985;3(1):179-196. 
  4. Garg D, Sharma S. Disease-Modifying Therapy in Subacute Sclerosing Panencephalitis: An Area of Darkness. Ann Indian Acad Neurol. 2023;26(1):3-9. doi:10.4103/aian.aian_655_22 
  5. Garg D, Patel S, Sankhla CS, et al. Movement Disorders in Patients with Subacute Sclerosing Panencephalitis: A Systematic Review. Mov Disord Clin Pract. 2024;11(7):770-785. doi:10.1002/mdc3.14062 
  6. Measles. Accessed November 9, 2025. https://www.who.int/news-room/fact-sheets/detail/measles 
  7. Measles vaccines. Accessed November 9, 2025. https://www.who.int/groups/global-advisory-committee-on-vaccine-safety/topics/measles-vaccines 

 

 

 

 

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