Delayed presentation of primary parenchymal arachnoid cyst in adult population: a rare location of a common cyst-case report and review of the literature

Background Arachnoid cysts account for about 1% of all intracranial mass lesions. Intraparenchymal arachnoid cysts are an uncommon entity. Only a few reports are available in adults with the intraparenchymal arachnoid cyst. Case presentation We present a 40-year-old lady with right-side progressive hemiparesis, and radiology revealed a cystic mass located in the left posterior frontal area. She underwent craniotomy and excision of the cyst. In the postoperative period, she recovered well. Immunohistochemistry stains confirm arachnoid cyst. Conclusion This was a case of a pure frontal arachnoid cyst with delayed clinical presentation without any communication with sub-arachnoid space or ventricle.