Subacute Sclerosing Panencepha... Health Article

Definition

Subacute sclerosing panencephalitis (SSPE) is a long-lasting (chronic) infection of the central nervous system that causes inflammation of the brain. The infection is caused by an altered form of the measles virus. The symptoms appear years after the initial infection, following re-activation of the latent virus.

Description

SSPE is one of three types of encephalitis that can occur following infection with the measles virus. The other forms are an acute (sudden appearance of symptoms) form that is typically associated with the rash that forms during the measles infection. The other form of SSPE affects the myelin sheath surrounding nerve cells, and is likely part of an autoimmune reaction.

SSPE develops when the measles virus, which is still present but is in an inactive (or latent) form, is reactivated. The appearance of symptoms typically leads to a disease that last from one to three years.

The disease is also known as subacute sclerosing leukencephalitis and Dawson's encephalitis.

Demographics

Children and young adults are primarily affected with SSPE. Males are also more affected than females, with a male-to-female ratio of 4:1. As well, there is a geographical component to the infection, with those in rural areas being much more susceptible (approximately 85% of cases arise in rural environments). Since the measles vaccine has been introduced, the disease has become rare in many areas of the globe, particularly the western world (about one in 1,000,000 people). Fewer than 10 cases per year occur in the United States. However, in the Middle East and India the incidence of the disease remains high (over 20 cases per 1,000,000 people).

Causes and symptoms

The disease is caused by the reactivated form of a mutated measles virus. The inactive form of the virus can be present in the body for up to 10 years following the initial bout of measles before the symptoms of SSPE develop. While normally the measles virus does not infect the brain, the mutated virus is capable of invading the brain.

When symptoms do develop, motor skills and mental faculties become progressively worse. Initial symptoms include a change in behavior, irritability, memory loss, and difficulty in forming thoughts and solving problems. Subsequently, a person can experience involuntary movements and seizures (also known as myoclonic spasms), loss of the ability to walk, difficulty speaking, and swallowing difficulty (dysphagia). Blindness can occur. In the final stages of the disease, a patient with SSPE may become mute and can lapse into a coma.

Monitoring the electrical activity of the brain has shown that SSPE causes disruptions that are consistent with the deterioration of the central nervous system. These changes tend to occur in stages, and so can be diagnostic of the progression of the disease. A different pattern of brain deterioration has been detected using the techniques of computed tomography and magnetic resonance imaging. However, this latter pattern is not yet refined enough for diagnostic use. Examination of brain tissue has shown that the disease is associated with the deterioration of the cortex and loss of white matter.