Prognosis of the Lennox Syndrome—Long-Term Clinical and Electroencephalographic Follow-up Study, Especially with Special Reference to Relationship with the West Syndrome

The long-term clinical and electroencepha-lographic follow-up studies were carried out for more than three years, up to 14 years in the longest, on 116 cases with Lennox syndrome. And the results of systematic study on changing patterns and outcome have been reported. The follow-up examination was performed also on West syndrome which is closely related with Lennox syndrome; especially the relationship between both syndromes regarding prognosis has been clarified.

• 1 According to the long-term follow-up on 116 cases with Lennox syndrome, there were 98 cases (84.5%) having mental defect. The remaining of seizure was observed in 71 cases (61.2%) and persisted as Lennox syndrome except for one case.
• 2 Generally speaking, the cases with age of onset before two years old showed unfavorable outcome.
• 3 There were 42 cases (36.2%), which were converted from West syndrome and showed markedly unfavorable prognosis in regard to intelligence as well as the remaining of seizure. (31 cases, 77.5%)
• 4 On the other hand, in 23 idiopathic cases, which showed no developmental retardation before onset of seizure, had favorable outcome, and the remaining of seizure was observed in eight cases (34.8%). However, even in such cases, it was noticed that those displaying mental defect at the follow-up attained 14 cases (60.9%). That is to say, it was clarified that persistence of even minor seizures induced mental deterioration.
• 5 The cases with favorable prognosis showed usually a typical slow spike-and-wave pattern electroencephalographically, whereas those with poor prognosis showed mostly an asymmetric or disorganized slow spike-and-wave pattern.
• 6 In many cases displaying signs of brain atrophy with pneumoencephalogram and accompanying overt neurological signs at the initial examination, prognosis is obviously poor.
• 7 From the follow-up examination on 94 cases with West syndrome for three to 15 years, there were 51 cases (54.3%) which was transformed into Lennox syndrome. Among them, those cases with the remaining of seizure at the time of follow-up were 44 (46.8%) out of 94 cases, of which 37 cases (83.8%) had remaining seizure as Lennox syndrome.
• 8 From the above results, it is emphasized that Lennox and West syndromes show close relationship with each other and that a study should be done on the interrelation between their prognosis.