OVERVIEW

What is subacute sclerosing panencephalitis?

Subacute sclerosing panencephalitis (SSPE) is a rare and fatal degenerative disease of the central nervous system caused by persistent chronic infection with the measles virus. It manifests as a panencephalitis primarily affecting the white and gray matter of the brain.

Children and adolescents are most susceptible, with symptoms including progressive ataxia, myoclonus, and chronic intellectual impairment. Some patients may also experience visual symptoms. The condition progressively worsens, with most patients dying within 1 to 3 years of onset.

Is subacute sclerosing panencephalitis common?

The disease is extremely rare.

The incidence of SSPE among measles patients is approximately 6 to 22 per 1 million people, primarily affecting children under 12 years of age. Among children infected with measles before the age of 5, the risk increases to about 730 cases per 1 million.

SSPE occurs worldwide but is more prevalent in Arab and Mediterranean countries, with higher incidence rates in rural areas compared to urban ones.

SYMPTOMS

What are the symptoms and manifestations of subacute sclerosing panencephalitis?

Subacute sclerosing panencephalitis primarily affects children and adolescents. Patients with childhood-onset cases may exhibit increasingly severe ataxia symptoms such as unsteady walking and standing, and inaccurate grasping. They may also experience recurrent brief limb jerking, along with progressive intellectual impairment.

Due to the retinal neurotropism of the measles virus, 50% of patients may develop visual symptoms, such as acute vision loss due to cortical blindness, visual-agnosia (inability to recognize common objects, though identification through touch remains possible), and visual hallucinations.

Additionally, there are some special types, including adult-onset subacute sclerosing panencephalitis and pregnancy-associated subacute sclerosing panencephalitis.

How does subacute sclerosing panencephalitis progress?

Typical patients with subacute sclerosing panencephalitis may have had a measles infection 2 years prior, followed by a 6–8-year asymptomatic latent period before gradual onset. The condition progresses subacutely or chronically, and although the rate of symptom progression varies among individuals, it generally worsens over time.

Typical subacute sclerosing panencephalitis can be divided into four stages based on its course:

• Stage 1 is the behavioral and psychiatric disorder phase, where affected children primarily exhibit forgetfulness, declining academic performance, emotional instability, personality changes, and behavioral abnormalities. Symptoms may be subtle and go unnoticed. This stage lasts from weeks to years.

• Stage 2 is the motor dysfunction phase, characterized by progressively severe cognitive decline, accompanied by widespread myoclonus (such as brief limb jerking triggered by sounds like speech), ataxia, seizures, aphasia, apraxia, and visual disturbances. This phase lasts several months.

• Stage 3 is the coma and opisthotonus phase, where children develop limb rigidity, hyperreflexia, Babinski sign, decorticate or decerebrate posturing, and possibly opisthotonus, eventually progressing to coma. This stage is often accompanied by high fever, excessive sweating, and unstable blood pressure and may last several months.

• Stage 4 is the terminal phase, marked by a vegetative state, complete loss of cortical function, ocular floating, hypotonia, and disappearance of myoclonus. The child ultimately dies from complications such as infections or circulatory failure.

What conditions should subacute sclerosing panencephalitis be differentiated from?

• First, it must be distinguished from other epileptic or dementia-related disorders in children and adolescents, such as lipid storage diseases, Schilder disease, myoclonic epilepsy, and mitochondrial encephalomyopathy.

• For adult-onset cases, abnormal brain signals should be differentiated from intracranial space-occupying lesions and demyelinating diseases.

• Pregnancy-associated cases require differentiation from cerebral venous thrombosis and eclampsia.

CAUSES

What are the causes of subacute sclerosing panencephalitis?

The occurrence of subacute sclerosing panencephalitis is currently believed to be caused by chronic infection with the measles virus. The mutated measles virus invades the nervous system in a dormant state and becomes activated 6–7 years after the primary measles infection, gradually attacking brain tissue and causing disease. The exact pathogenesis is still not fully understood.

DIAGNOSIS

How is subacute sclerosing panencephalitis diagnosed?

The diagnosis is primarily based on the typical disease course and clinical manifestations, supplemented by tests such as cerebrospinal fluid analysis and measles antibody detection. Brain biopsy revealing panencephalitis lesions, intracytoplasmic inclusions, or measles virus particles, as well as isolation of measles virus from brain tissue, can confirm the diagnosis.

What tests are required for patients with subacute sclerosing panencephalitis, and why are these tests necessary?

• Lumbar puncture: Obtaining cerebrospinal fluid samples allows detection of measles virus-specific plasma cells and oligoclonal bands, while also helping to rule out other intracranial infectious diseases.

• Serum and cerebrospinal fluid measles (rubella) virus antibody titers: Assists in determining whether there is measles virus infection in the body.

• Electroencephalogram (EEG): Subacute sclerosing panencephalitis exhibits different EEG characteristics at various disease stages, and follow-up observations aid in auxiliary diagnosis. Patients in clinical stage 2 may show high-voltage complex waves composed of 2–3 Hz slow waves and sharp waves, sometimes followed by mild suppression, which is a characteristic manifestation of the disease and may have diagnostic significance.

• Head CT, MRI, or functional imaging: Identifies brain tissue damage and features while excluding conditions such as intracranial tumors.

• Brain biopsy: Isolation of measles virus can confirm the diagnosis.

Lumbar puncture is often required for subacute sclerosing panencephalitis. What precautions should be taken for this test?

Lumbar puncture is an invasive procedure involving needle insertion into the spinal canal to collect cerebrospinal fluid samples. This test is essential for determining the presence of intracranial infections or other conditions because the blood-brain barrier, which normally protects brain tissue from toxins or pathogens in the blood, also prevents blood tests from accurately reflecting intracranial conditions.

Cerebrospinal fluid surrounds the brain and spinal cord, and abnormalities in this fluid may indicate intracranial infections. Since cerebrospinal fluid is continuously produced and absorbed in the body, collecting a sample has no adverse effects.

The procedure is performed by inserting a needle into a specific area of the lower back, where cerebrospinal fluid can be safely collected without damaging the spinal cord or nerves. Patients must cooperate by maintaining a specific position and minimizing movement. Local anesthesia is applied to reduce discomfort, though some sensations may still be felt. After the procedure, patients should lie flat without a pillow for 6 hours and drink plenty of fluids to minimize post-puncture headaches caused by cerebrospinal fluid pressure changes. Normal activities can be resumed afterward.

TREATMENT

Which department should I visit for subacute sclerosing panencephalitis?

Pediatric Neurology, Pediatrics, Neurology, Infectious Diseases.

Can subacute sclerosing panencephalitis heal on its own?

No.

Does subacute sclerosing panencephalitis require hospitalization?

Usually, yes.

How is subacute sclerosing panencephalitis treated?

There is currently no specific cure for this disease. Antiepileptic drugs and other supportive treatments against measles are the only acceptable options. The use of inosiplex, interferon-alpha, and lamivudine is controversial, and antiviral drugs generally do not help.

Therefore, the main treatment focuses on symptomatic support and preventing complications, such as using antiepileptic drugs for myoclonic seizures and maintaining fluid and electrolyte balance. Intensive nursing care is also needed to reduce risks like bedsores and hypostatic pneumonia.

DIET & LIFESTYLE

What should patients with subacute sclerosing panencephalitis pay attention to in their diet?

If oral intake is possible, it is recommended to strengthen nutrition and increase the intake of vitamins. If eating is difficult due to mental state or seizures, nasogastric tube feeding with liquid diet is advised.

What should patients with subacute sclerosing panencephalitis pay attention to in daily life?

• For those with epilepsy, avoid factors that may trigger seizures, such as consuming stimulating beverages or exposure to flashing lights.

• Patients may experience cognitive and visual impairments, so family members should provide close supervision to prevent accidents like wandering.

• In later stages, as the disease progresses, patients often become bedridden, requiring enhanced care to reduce complications.

PREVENTION

Can Subacute Sclerosing Panencephalitis Be Prevented?

Following the recommended vaccination schedule and avoiding contact with or proximity to measles patients can reduce the risk of contracting measles, thereby lowering the risk of developing subacute sclerosing panencephalitis.