Long-term studies on patients with absence and bilateral spike-wave complexes: 430 patients, up to 52 years follow-up

This study involved long-term changes, up to 52 yrs, in 430 patients with absence (A) attacks and bilateral spike and wave complexes (BSW). Nearly 2/3 had additional GTC attacks and only about 1/4 had A alone. Atonic attacks (7%), complex partial (CP) (4%) and other types of seizures also occurred in the group. Distinctive features of the GTC group were diffuse slow waves and 6/sec spike and wave complexes, and of the A alone were BSW as the only abnormality and later normal records. For CP or focal motor (FM) attacks, nearly all had focal spikes and these seizures appeared between 15-25 yrs of age. The background alpha rhythm with increasing age showed more rhythmicity, but lower amplitudes in all of these patients. Onset age was an important factor in that the highest peak was at 6 yrs, mainly from those with A only and a minor peak appeared at 13-14 yrs, mainly from the patients with GTC seizures. One major difference between the group with A alone and those with GTC attacks was that normal records developing with A alone usually remained normal, while those with GTC attacks usually became abnormal again. The 6/sec spike and wave complexes usually appeared after the onset of GTC attacks, often at 18-19 yrs of age. Diffuse slowing usually appeared after GTC attacks at around 16 yrs after the onset of these seizures. Possible forerunners of BSW were multifocal spikes at < 4 yrs of age, occipital or temporal spikes at 5-16 yrs and temporal spikes after 16 yrs of age. CP seizures could be predicted from the EEG by focal spikes, especially on the temporal lobe, appearing over long periods of time in records with an inconsistent BSW. Patients with A extending into adulthood were distinctive by a later onset of A and a history of GTC attacks. In general, more females were seen in this study but there were more males with A alone and more developed a normal record. Females often had a later onset of A, with GTC attacks, and the older the patient in this study the more likely the patient was female. Evidence is seen in this study for prediction of (1) future BSW by different types of focal spikes at different ages, (2) CP (or FM) seizures by focal spikes and an inconsistent BSW, (3) GTC seizures by onset age, female sex, and EEG reverting to an abnormal record after normalizing, (4) A attacks alone by onset age, male sex and finally a normalized EEG, and (5) GTC or myoclonic attacks by the presence of BSW as the only abnormality.