Resumen

SANTIN, Julia et al. Incidence of normal variants patterns that mimic epileptiform discharges in routine normal EEGs: Prospective study and literature review. Rev. chil. neuro-psiquiatr. [online]. 2003, vol.41, n.4, pp.281-290. ISSN 0717-9227.  http://dx.doi.org/10.4067/S0717-92272003000400004.

Normal EEG variants recognition is very important in order to reduce diagnostic errors in epilepsy. There are no reports in our country regarding this EEG activity, and in regular practice only one of them it is mentioned ocassionally, which prompted us to investigate this issue. Objective. To establish the incidence of normal variants in routine EEGs in a laboratory population older than a year. Methods. The presence of normal variants (wicket spikes, 14 and 6 positive spikes, psychomotor variant, small spikes of sleep, slow waves of the elderly, pseudo petit mal, arousal theta, dicrotic alpha, µ rhythm, phantom spikes and rhythmic subclinic discharges of the adult) was studied prospectively in all routine EEGs (standard and after sleep deprivation) performed in patients older than one year at the EEG laboratory of the Hospital Clínico de la Universidad Católica de Chile between october 1999 and September 2000. All the records were read by one of the authors. Results. From a total number of 1816 normal EEG recordings, 4,8% (n=88) showed normal variants, reaching in patients over 60 years old to 11,4%. Within the normal variants the most frequently found were µ rhythm (45,5%), wicket spikes (21,6%) and psychonmotor variant (9,1%). No phantom spikes neither subclinical rhytmic discharges of the adult were found. Conclusion. Normal variants are found not infrequently in normal routine EEGs in our country, specially in patients over 60; it is convenient to have them in mind for avoiding overdiagnosis of epileptiform activity

Palabras clave : normal EEG variants; normal EEG patterns; EEG rhythms.