Prolonged and variable intervals between EEG complexes in subacute inclusion body encephalitis.

Should effective therapy of SIBE ever depend upon early diagnosis, periodic EEG complexes must be sought carefully when the condition is suspected, bearing in mind that initially the duration of intervals between complexes may be more prolonged and more variable than commonly appreciated. Prolonged, uninterrupted recording at reduced speed, taken both while the patient is awake and asleep, may well facilitate recognition of periodic events as unusual as those observed in the 20-year-old young man described in this paper, who was examined during the early stage of the disease. When initial EEG complexes are separated, as in our patient, by variable and prolonged intervals - up to 86 seconds' duration - their periodicity and diagnostic implication can be overlooked, particularly in a so-called routine electroencephalogram. Optimal dispaly of such unusual findings calls for suitable electroencephalographic techniques.