Substantial spontaneous long-term improvement in subacute sclerosing panencephalitis. Six cases from the Middle East and a review of the literature.

Of 118 cases of subacute sclerosing panencephalitis identified in an extensive follow-up study in the Middle East, six patients were found by personal interview to have experienced substantial spontaneous long-term improvement. To our knowledge, this rate of 5% for such improvement is presently the most accurate estimate available. Relative to the onset of clinical illness, the conditions of two patients are still improving four to five years later, two are stable four to six years later, one relapsed and died recently after eight years, and one is currently in relapse after 11 years. The condition of five patients had not progressed beyond stage 2 before improvement began. All patients had characteristic clinical and electroencephalographic features. Two patients had brain biopsy specimens showing panencephalitis without inclusions. Five patients had highly elevated levels of serum and CSF measles antibodies. In this article, the course of illness and extent of disability are described, published reports of improvement are reviewed, and the possibility of subclinical illness is discussed.