Interhemispheric arachnoid cyst.

[BACKGROUND] Interhemispheric arachnoid cysts are uncommon and typically associated with other midline neurodevelopmental disorders, such as complete or partial agenesis of the corpus callosum.

[CASE DESCRIPTION] We report a case of a 27-year-old woman with worsening headache, memory deficit, and radiological progression of an interhemispheric arachnoid cyst. The treatment consisted of craniotomy for interhemispheric cyst fenestration into both the interhemispheric cistern and lateral ventricle. The postoperative course was unremarkable, with considerable clinical improvement and significant reduction in cyst size.

[CONCLUSION] We successfully treat a patient with an enlarging arachnoid cyst and associated progressive symptoms with microsurgical fenestration.