Radical resection for intrinsic midbrain pilocytic astrocytoma: report of two cases.

BACKGROUND: Intrinsic midbrain glioma has been one of the most challenging therapeutic tasks in neurosurgery due to its prognosis and risks associated with surgical procedures. It is known that the prognosis of pilocytic astrocytoma is relatively good if radical resection can be achieved without severe complications. In order to remove pilocytic astrocytoma within the midbrain radically, we used microsurgical techniques.

METHOD: Two patients with intrinsic pilocytic astrocytomas located at the midbrain were operated on. The subtemporal approach was used with a point of entry on the lateral surface of the midbrain just behind the cerebral peduncle. Major vessels were preserved, followed by resection of the intrinsic tumor making the cleavage between tumour and midbrain.

FINDINGS: In both patients, intrinsic pilocytic astrocytoma was grossly totally removed with minimal permanent morbidity. They have been able to maintain independent activities in their daily lives without tumor recurrance.

CONCLUSIONS: Surgical cure can be accomplished in some cases of midbrain pilocytic astrocytoma, even if the lesions are intrinsic to the midbrain. To remove the tumor totally without further neurological deficits, it is necessary to select a safe access or entrance point to the tumor, and to demarcate the gliotic plane between tumour and midbrain. A long-term follow up with a larger number of patients is needed to establish the significance of radical resection for intrinsic midbrain pilocytic astrocytoma.