Cavum vergae, cavum septum pellucidum and cavum veli interpositi are brain midline embryological developmental cysts. They are rarely seen after trauma. Generally, they do not constitute clinical findings. These cysts sometimes become enlarged and become symptomatic. Enlarged cysts cause severe neurological dysfunction. During normal fetal development, the development of the adjacent structures of the limbic system and the septum pellucidum are synchronized. It is thought that dysgenesis in these adjacent structures may affect the lamina fusion of septum pellucidum and cause cavum septum pellucidum. Anterior one of the cavities that arise when septum pellucidum laminae do not join after birth is called “cavum septum pellucidum” (CSP). The one in the posterior is called “cavum vergae” (CV). Velum interpositum (VI) is a potential cavity below the corpus callosum splenium and sometimes presents as a cyst. Cavum veli interpositi (CVI) is located in the pineal area, below the columna fornicis and above the tela choroidea of the 3rd ventricle. Because of its rarity, the incidence of CVI cyst is uncertain. The CV obliterates from the front to the front and is seen with the cavum septum pellucidum. CSP and CV are cavities that are present in fetal life but are considered as variant intracranial defects that do not close 6 months after birth. CVI is rarely seen embryo logically in fetal life in children over 2 years and adults. These cysts are rare in adults. In this study, anatomical features and clinical reflections of CSP, CV and CVI were reviewed.