MULTIPLE-SCLEROSIS - PATHOLOGY OF RECURRENT LESIONS

Recent autopsy studies suggest that remyelinated shadow plaques locate d in otherwise intact white matter are the outcome of a previous singl e episode of acute demyelination. In the present study, of 98 remyelin ated plaques examined in 15 patients with multiple sclerosis who died between 27 days and 5 years after clinical onset, 15 showed evidence o f a superimposed new demyelinating lesion. Inspection of old shadow pl aques in a separate series of patients with subacute and long-standing multiple sclerosis revealed that such lesions sometimes exhibit punch ed-out areas of demyelination and gliosis similar in size and shape to fresh lesions located within or overlapping remyelinated shadow plaqu es. The findings support magnetic resonance imaging evidence that loca l recurrence may be as important or more important than progressive ed ge activity in determining plaque growth and the conversion of nascent lesions into classical demyelinated plaques. The findings also suppor t experimental evidence that recurrent demyelination of the same area of white matter may be one of the factors underlying failed remyelinat ion in multiple sclerosis.