We report the case of a 55-year-old patient with infrequent generalized tonic-clonic seizures since the age of 40 years and additional frequent episodes of disturbed behaviour and impaired cognition. The latter last from several hours up to one day with sudden onset and end of electroencephalographic (EEG) changes and clinical manifestations. They occurred about once a week before they were successfully treated with valproate and lamotrigine. From clinical, therapeutic and EEG findings we conclude that the patient suffers from nonconvulsive status epileptici, although the ictal EEG showed an untypical pattern of monomorphic generalized alpha rhythm. Many EEG characteristics point towards a primary generalized seizure disorder but a focal origin with secondary bilateral synchrony has to be considered as well. However, this is obviously a rare type which has not been described previously.