An Overview of Subacute Sclerosing Panencephalitis (SSPE)

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Sometimes called Dawson’s disease or Dawson’s encephalitis, subacute sclerosing panencephalitis (SSPE) is a rare but fatal neurological disorder caused by the measles virus that typically appears years after the individual has recovered from measles. Early symptoms are often subtle changes to mood or behavior, but they get more serious and debilitating as the disease progresses. There’s no cure for SSPE, and it’s nearly always fatal. The only real defense against SSPE is preventing measles altogether through widespread vaccination.

Symptoms

Symptoms of SSPE start as subtle neurological changes and eventually progress to a complete shutdown of the central nervous system. The condition generally progresses in four stages.

  • Stage I: Early symptoms of the disease include personality or behavior changes, including mood swings or depression. In some cases, individuals with SSPE might also have a headache or fever. 
  • Stage II: Symptoms become more obvious, ranging from uncontrolled movement or spasms, seizures, dementia, or vision loss.
  • Stage III: Involuntary jerking movements get more pronounced (ex. writhing) and muscles can become rigid.
  • Stage IV: Brain damage starts to affect breathing, blood pressure, and heart rate, eventually leading to coma or death.

These symptoms typically appear between six to eight years after recovering from a measles infection, but they can appear as early as a few months later.

SSPE is almost always fatal. Nearly everyone with the condition will die within a few years of being diagnosed.

Causes

SSPE is a serious complication caused by an infection from the measles virus. Unlike other measles complications like encephalitis or pneumonia, SSPE is a long-term complication that doesn’t show up for months or—more commonly—years after someone appears to have recovered from measles. 

Not everyone who gets measles develops SSPE, and it’s unclear why the virus affects the brain so severely in some but not in others. Some researchers think a mutant strain of the virus is more likely to attack the brain, while others believe the body’s own reaction to a measles infection might be what sparks the deterioration process. Either way, the result is swelling and irritation in the brain that can last for years, resulting in brain damage and death.

Risk Factors 

Certain groups of people are more likely to develop SSPE than others, including: 

  • Kids and teens
  • Males 
  • Children in rural or overcrowded areas
  • Children infected with measles at a young age

Early infection with measles might be one of the greatest risk factors for SSPE. For example, one study in Germany found that SSPE was significantly more common in those who were infected at a young age (before age 5). In the study, researchers calculated the risk of SSPE for these kids to be as high as 1 in 1,700.

The risk is even more pronounced for babies. Children who get infected with measles in their first 12 months are 16 times more likely to get SSPE than those who get the disease at age 5 years or older. Most children do not get vaccinated against measles until they are at least 12 months old.

While the measles vaccine does contain live (but severely weakened) measles virus, measles vaccination doesn’t appear to cause SSPE. In fact, high vaccination rates against measles have been followed by a steep drop in SSPE cases.

Diagnosis

Because the symptoms of SSPE can look like other behavioral or neurological conditions, doctors typically use a combination of tools and tests to diagnose the condition, including a physical exam, electroencephalogram, MRI, and antibody titer test.

Physical Exam

During a physical exam, doctors will likely look for signs that the central nervous system is failing by looking at parts of the eyes or testing how well muscles can coordinate. They’ll also ask about the individual’s medical history—specifically, whether they have had measles or been vaccinated against it. 

The doctor might also order some additional tests to confirm the diagnosis and determine what stage of SSPE someone might be in.

Electroencephalogram

Electroencephalograms (EEGs) measure the brain’s electrical activity. During this test, small metal discs (called electrodes) are placed all over the head to capture and record electrical signals while doing certain activities like taking quick breaths or looking at a bright light.

EEGs can help doctors spot abnormal electrical signals in the brain that could signal neurological issues like SSPE, as well as how far along the condition might be. In the early stages of SSPE, EEG results might come back normal, so a doctor might want to repeat the test over time.

Brain MRI

Brain MRI (magnetic resonance imaging) tests use powerful magnetic fields and radio waves to generate images of the brain. Doctors use this test to see what specific parts of the brain might be affected by SSPE.

Serum Antibody Titer

Titer tests look for signs that the body has been exposed to a particular germ. In the case of SSPE, doctors use these tests to look for measles antibody titers in fluid found in the brain or spine.

Treatment

There’s no cure for SSPE. Treatment for the condition typically involves managing the symptoms, such as using anti-seizure medication. Antiviral drugs and medicines that boost the immune system are sometimes also prescribed to slow the progression of the condition.

While medications can prolong or improve quality of life for those with SSPE, the only real way to stop it is to prevent measles infections from the start.

Prevention

SSPE can be prevented by getting vaccinated against measles. Doctors recommend two doses of measles vaccine—given as part of the measles, mumps, and rubella (MMR) vaccine — at age 12-15 months and at 4-6 years, though older children and many adults can also get vaccinated if they hadn’t been previously. 

Not everyone can be vaccinated against measles. The vaccine isn’t recommended for most babies under 12 months old, as well as pregnant women and those with weakened immune systems (ex. cancer patients receiving treatment). These individuals rely on high community vaccination coverage rates to protect them from measles.

A Word From Verywell

SSPE is a serious condition, but it’s extremely rare in areas with high measles vaccination rates. Those with questions or concerns regarding the MMR vaccine should talk to their doctor.

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