Neuro-endoscopic management of mesencephalic intraparenchymal cyst: a case report

Intraparenchymal cyst of the mesencephalon is rare, and its natural course is unclear. The optimal treatment for this entity is still undetermined.

A 54-year-old woman was found to have asymptomatic multilobulated mesencephalic cysts. Two years after the initial diagnosis, she experienced headache and double vision, when MRI showed the enlargement of the multilobulated cystic lesions which markedly compressed the mesencephalon and the aqueduct, resulting in noncommunicating hydrocephalus. She underwent diagnostic endoscopic biopsy and ETV by flexible endoscopic system, which revealed the mesensephalic cyst wall at the dorsal part of the third ventricle floor. A part of the cyst membrane was carefully excised by endoscopic forceps without injuring the surrounding structures. Histopathological examination revealed that the cyst wall was exclusively neuroglial tissue, and the presence of neoplasm was ruled out. Her symptoms were relieved immediately after surgery, and postoperative MRI showed both the shrinkage of mesencephalic cysts and the improvement of hydrocephalus. There is no recurrence of her symptoms, and MRI findings have been stable during the 3 year follow-up period.

Intraparenchymal cysts of the mesencephalon have an expanding nature. Once those cysts become symptomatic, we recommend endoscopic procedure including decompression and biopsy of the cyst with ETV.