(Rev Méd Chile 2003; 131: 1280-87).

A sisternatic clinical protocol was applied in 16 infants that suffered from infantile spasms (IS) in order to identify etiologic factors. A positive family history was present in 2/16 patients and relevant perinatal or postnatal pathology in 5/16. Psychomotor retardation and other seizures anteceded IS in 10/16 and 8/16 infants respectively. Physical and neurologic examination revealed mycrocephalia 14/16), dismorphic features (2/16), hypopigmented skin lesions (1/16) and piramidal syndrome (8/16). Neuroimagine technics yielded positive findings in 9/16 patients, d if use or localized atrophy (7/16), porencephalic cysts (3/16), periventricular calcifications (1/16), callosal agenesis (1/16). Laboratory examination allowed diagnosis of two metabolic diseases: congenital hiperlactatemia an maple syrup urine disease. Two patients were classified as criptogenetic and fourteen as symptomatic. Within the latter an etiologic factor was identified in 12/14. This study underlines the value of etiologic search in IS, because it may contribute substantially to specific treatment and genetic counselling. Se denomina espasmos masivos (EM) a un si'ndrome epileptico grave, propio del lactante, descrito por W. J. West en 1841 \ caracterizado por espasmos breves en salvas. Los pacientes usualmente presentan retardo moderado o severo de base y evolucionan con deterioro psicomotor. El trazado electroencefalografico caracteristico es la hipsarritmia 2 . La incidencia de EM se ha estimado entre 0,24-0,42 x 1 000 recien nacidos 3 ' 4 y su etiologia es diversa, diferenciandose dos grupos de importancia pronostica: los EM sintomaticos, en que los pacientes tienen alteracion neurologica o retardo psicomotor antes del inicio de los espasmos o un factor etiologico demostrable por estudios, y los EM criptogeneticos, que ocurren en ninos con desarrollo normal y sin antecedentes de enfermedades neurologicas antes de comenzar el cuadro, en los que no se puede identificar un