The present study examined the clinical significance of anterior bradyrhythmia (AB), which was described by Gibbs and Gibbs in 1964. The significance of AB in this report was indefinite because of unclear criteria and underdeveloped neuroradiology. We proposed a set of criteria of AB and reevaluated the clinical significance of the EEG pattern in correlation with the clinical and the computerized topography (CT) findings of the patients. The study material was 4019 EEGs examined in our laboratory during a 1-year period (1991). AB was recorded in 20 patients (0.5%), whose mean age was 69.8 years. Its incidence tended to increase with age. Sixteen patients [table: see text] (80%) had dementia and were classified into two types according to clinical features, as Binswanger (B)-type and Alzheimer (A)-type. B-type patients had gait disturbance, urinary incontinence, hemiparesis, and ECG abnormalities, and showed leuko-araiosis on CT. A-type patients had only dementia, and showed frontoparietal atrophy on CT. Delirium was found in 7 (35%) out of the 20 patients with AB, which may be an additional factor related to the appearance of the EEG pattern. B-type had lower frequency of AB than A-type. Both types showed slowed background activities; the alpha rhythm of B-type had lower frequency and tended to have higher amplitude than that of A-type. These EEG abnormalities may be indicative of subcortical or cortical dysfunction in the frontal areas.

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