Intraoperative electrocorticography-guided resection of the epileptogenic zone in an unusual porencephalic cyst: case report and literature review.

INTRODUCTION: Porencephalic cysts resulting from perinatal artery infarctions typically manifest as large cysts accompanied by pre-existing neurological deficits. A small porencephalic cyst without any neurological deficit is a rare cause of medically refractory epilepsy.

CASE PRESENTATION: A 23-year-old female presented with a history of medically refractory epilepsy secondary to a small right parieto-temporal porencephalic cyst. Despite optimal anti-seizure medications, seizures persisted. Surgical intervention was planned, and intraoperative electrocorticography (ioECoG) was used to delineate the epileptogenic zone (EZ), which was found to be two gyri posterior to the cyst.

DISCUSSION: Very focal ischaemia resulting in a small porencephalic cyst from perinatal artery infarction exhibits a distinct organization of the EZ involving wider area posteriorly indicating involvement of arterial territory distal to the cyst. This contrasts with the typical perilesional EZ observed in other lesional epilepsy causes.

CONCLUSION: Our findings emphasize the need to consider aetiology during interpretation of ioECoG to better define the electrophysiological border between the normal and epileptogenic brain, aiding in achieving a better surgical outcome.