iarjmsIARJMSIARJMS2708-359410.47310/iarjms.2021.v02i01.034An Unusual Coexistence of Central Precocious Puberty and Intraventricular Arachnoid Cyst in a GirlGonzaloOliván-GonzalvoJoséIgnacioPerales-MartínezMassimoFelicianiVicenteCalatayud-MaldonadoPediatrics and International Adoption Center, Pediatrics Service, Zaragoza, SpainPilar Clinic, Pediatric Endocrinology Service, Zaragoza, SpainCentre Médics Creu Blanca, Neuroradiology Service, Barcelona, SpainNeurosciences Institute of Aragón, Neurosurgery Service, Zaragoza, SpainCentral precocious puberty (CPP) is a rare disease. In Spain, the annual incidence in girls ranges from 0.13-2.17 new cases per 100,000. CPP in girls is usually idiopathic. Only 7-15% is related to an intracranial lesion. Intracranial arachnoid cysts are usually congenital account for 1% of intracranial masses in newborns. Intraventricular location is rare, account only 0.3-1.4%. Intracranial arachnoid cysts are usually asymptomatic but can present with CPP in 10-33% of patients. We report a case of a 7-year-old-girl presenting the unusual coexistence of CPP and a neurologically asymptomatic intraventricular arachnoid cyst. The etiopathogenesis of this association is not well recognized. Analysis of LH peaks after GnRH testing is the gold standard for the diagnosis of CPP. Although central nervous system disorders account for a higher percentage of cases in boys with CPP, they must also be excluded in girls. In this patient, brain MRI did not show hypothalamic-pituitary axis alterations or the existence of hydrocephalus, so we cannot prove a causal relationship between the intraventricular arachnoid cyst and CPP. Therefore, this coexistence may be only accidental. However, we emphasize that all girls with CPP should undergo brain MRI as part of their evaluation, as clinical characteristics, including age, do not help to predict underlying pathologies. Cyst surgery does no affect the course of pubertal development. There seems to be a consensus that in pediatric patients the indication for surgery is seizure onset, hydrocephalus, ruptured/hemorrhaged, and mass effect or slow-growing clinical course.