Noncommunicating interhemispheric cysts, such as interhemispheric arachnoid cyst or ependymal cyst, with callosal agenesis are also in the second category. A careful review of embryologic development is essential for understanding these midline cysts and for making a more accurate radiologic diagnosis ¹⁾.

Two cases of symptomatic interhemispheric arachnoid cyst (IHAC) in the elderly, both extending into the frontoparietal region. Both patients presented with more than an 8-year history of progressive hemiparesis and underwent capsule resection in combination with internal drainage to the pericallosal cistern via the interhemispheric approach. Postoperatively, the cyst cavities were greatly reduced in size, and neurologic signs and symptoms were markedly improved ²⁾.