A giant cerebral aneurysm is one that reaches a size greater than 25 mm in diameter, and whose complications are rupture and a mass effect like a tumor. The complex anatomy of the posterior communicating segment and the size of the aneurysm make it challenging to treat surgically, so the best definitive treatment option for this type of pathology is the Endovascular route, which seeks obliteration and exclusion of the aneurysm

In epilepsy refractory to medical treatment which presents multiple and bilateral epileptogenic foci such as Lennox Gastaut syndrome (LGS) the surgical alternative is disconnection surgery such as callosotomy. Posterior callosotomy is indicated in cases of atonic seizures with posterior resection, leading to better seizure control. We present the case of a patient with Lennox Gastaut syndrome who required a posterior callosotomy achieving complete control of atonic seizures.