RESUMO
INTRODUCTION: Prenatal intracranial anomalies of a cystic nature are mainly either malformations (arachnoid cysts) or disruptive (porencephaly). They are usually incidental findings and, unless they undergo a progressive increase in size and become expansile or offer clinical features, they are usually managed 'expectantly'. Disruptive defects are more frequent in twin pregnancies. CASE REPORT: A one and a half-month-old male patient, fruit of a bichorial twin pregnancy, with bouts of paleness, cyanosis around the mouth and movements of the mouth that initially responded to treatment with valproate. Physical exploration was normal except for a significant increase in the cephalic perimeter. A notable anaemia was observed and neuroimaging revealed a left temporal intraparenchymatous cystic lesion; in addition, magnetic resonance imaging showed alterations in the linear and symmetrical signals in the parasagittal region. At three months the seizures reappeared and the cyst had increased in size, which led to the implantation of a cyst peritoneal shunt. The seizures ceased and the size of the cyst became stable, without full re expansion of the brain tissue. DISCUSSION: It is necessary to carry out a differential diagnosis of an arachnoid cyst and porencephaly. Given the history of being a twin, the notable degree of anaemia at the age of one month and the image suggesting parasagittal cerebral injury (a pattern of hypoxic ischemic encephalopathy in the full term neonate), we think that our patient was suffering from antenatal or perinatal cerebrovascular damage, which conditioned the development of an expansile porencephalic cyst and cortical damage that accounted for the symptoms of epilepsy.
