The electroencephalograms (EEGs) of 22 patients suffering from hereditary DRPLA were studied. Epileptoform patterns were observed in 14 patients (63.6%) with epileptic seizures. The epileptoform patterns most frequently observed were those atypical spike‐wave complexes. Slow wave bursts were seen in 18 patients (81.8%). Photosensitivity was revealed in six (27.3%) patients, all of whom presented progressive myoclonus epilepsy (PME) syndrome. Abnormal background activity was evident in 17 (77.3%) patients. These abnormalities in EEG were more severe in patients in the PME type than those of the A (ataxia) and AE (ataxia and epilepsy) types.

Phenotypes of apolipoprotein E (apoE) were determined with an isoelectric focusing method in 39 patients with sporadic Alzheimer's disease (AD), 3 8 patients with dementia from cerebrovascular disease (CVD), and 100 healthy subjects without hyperlipidemia. There was a striking difference in the distribution of apoE phenotypes between patients with AD and healthy subjects (p<0.001). Such a difference was attributable to different frequencies of phenotype E4/3 and E3/3. The apoE4/ 3 phenotype was detected in 38.5% (15 of 39) patients with AD, more than 3 times higher than in healthy subjects (12.0%, 12 of 100). In contrast, apoE3 / 3 phenotype, a wild type apoE phenotype, was detected in 81.0% (81 of 100) of healthy subjects but only in 38.5% (15 of 39) of patients with AD. The frequency of apoE-E4 allele assessed on the basis of obtained apoE phenotypes in patients with AD (0.269) was significantly higher than that in healthy subjects (0.08, p<0.001) and in patients with dementia from CVD (0.118, p<0.01). Furthermore, the frequencies of apoE-E4 in AD were 0.190 in patients older than 70 years and 0.333 in patients younger than 70 years. These results indicate a strong association between apoE-e4 and sporadic AD and suggest that apoE-e4 assessed from apoE phenotypes may be a possible risk factor for AD.