1 - Departamento de Neurorradiologia do Centro Hospitalar Universitário de Lisboa Central, Lisboa, Portugal
2 - Departamento de Neuropediatria do Centro Hospitalar Universitário de Lisboa Central, Portugal
3 - Centro de Responsabilidade Integrado de Medicina e Cirurgia Fetal do Centro Hospitalar Universitário de Lisboa Central, Lisboa, Portugal
- XVII Congresso da SPNR, 25 e 26 de Novembro de 2022, Lisboa
Introduction: Primary arachnoid cysts are benign intra-arachnoidal accumulations of clear cerebrospinal fluid, that are most commonly found in the middle cranial fossa, anterior to the temporal lobes (50-60%). Although their etiology is thought to be congenital, most cases of arachnoid cysts diagnosed prenatally are found in different locations. This poses the question: do middle cranial fossa arachnoid cysts, the most frequent in the adult and pediatric population, arise in utero or form later in life through different mechanisms?
Methods: We present two cases of a child and an infant studied using fetal and postnatal MRIs. Fetal MRIs were performed at 23 and 27 weeks of gestation for the first case, and at 24, 28 and 32 weeks of gestation for the second one. Postnatal MRIs were performed at 5 months and 4 years of age for the first case, and at 4 and 12 months for the second case.
Results: Our patients presented with diffuse subarachnoid space enlargement diagnosed prenatally through fetal MRI, which postnatally evolved to middle cranial fossa arachnoid cysts and benign enlargement of the subarachnoid space in infancy. Additionally, one of the cases also presented with a mega cisterna magna and the other with a frontal arachnoid cyst.
Conclusion: To our knowledge, these are the first cases in the literature reporting the progression from diffuse subarachnoid space enlargement to arachnoid cyst development. Considering the latter, we propose that some middle cranial fossa arachnoid cysts might result from subarachnoid space enlargement during the fetal period, although further evidence is needed to support this hypothesis.
Keywords: arachnoid cysts; fetal MRI; subarachnoid space enlargement;