Subacute Sclerosing Panencephalitis (Dawson Disease)

What is Subacute Sclerosing Panencephalitis?

Subacute sclerosing panencephalitis (SSPE) is a chronic persistent infection of the central nervous system caused by an altered form of the measles virus. It affects primarily children and young adults and usually has a progressive downhill course which results in death within a few years in most patients with a 5% chance of spontaneous remission. It can occur anywhere from 2 to 10 years after the original measles illness, and generally results in progressive neurological deterioration due to brain inflammation and nerve cell death. Since the widespread use of the measles vaccine, SSPE has become very rare. However, studies have shown that the incidence of SSPE has remained high in the Middle East and India. Initial symptoms usually include abnormal behaviour, irritability, intellectual deterioration, and memory loss which may be followed by involuntary movements and seizures (in the form of myoclonic spasms). Subsequently, the patient develops further mental deterioration, inability to walk, speech impairment with poor comprehension, and difficulty swallowing (dysphagia). Blindness may also result. In the final stages of disease, the patient may remain mute or comatose. The electrical activity of the brain, as recorded by electroencephalogram (EEG), shows progressive changes during the disease which are typical of SSEP and parallel the slow deterioration of central nervous system functions. A number of clinical staging scales have been used for several decades to categorize patients with SSPE according to their corresponding clinical status. More recently, a different staging system was developed based on the radiological findings of the brain by computed tomography (CT) and magnetic resonance imaging (MRI). This method, however, has not succeeded in establishing a complete correlation between radiological abnormalities and clinical progress.

Is there any treatment?

For several decades, the palliative treatment for SSPE has included anticonvulsant therapy and supportive measures (tube feedings and good nursing care especially in patients with advanced disease). Medical literature during the last decade, however, has shown stabilization of disease and delay in clinical progression after therapy with inosine pranobex (oral Isoprinosine); oral isoprinosine combined with intrathecal or intraventricular interferon alpha (up to 50% rate of remission or improvement); oral isoprinosine combined with interferon beta; and intrathecal interferon alpha combined with I.V. ribavirin. However, no controlled studies have been performed. The Food and Drug Administration has added inosine pranobex (Isoprinosine) to its List of Orphan Products Designations and Approvals (1988) for the treatment of SSPE.

What is the prognosis?

When not treated with immunomodulators (interferon) and antivirals (ribavirin and inosine pranobex) SSPE is almost always a fatal disease. Death usually occurs between 1 and 3 years after onset, although some spontaneous remissions (up to 5%) have been reported.