Occipital Interhemispheric Retrocallosal Transtentorial Approach to a Tectal Tumor in an 8-Year-Old Girl: Operative Video.

ABSTRACT

Tectal plate tumors are a rare subset of midbrain tumors in pediatric populations. They are slow growing and low grade, with indolent and subtle manifestation unless they cause hydrocephalus.1-5 We present a tectal tumor in an 8-year-old girl (Video 1). Her clinical onset occurred with headache, vomiting, and seizure secondary to intracranial hypertension. MRI revealed a ring-enhanced, roundish lesion of tectal plate, with posterior displacement of quadrigeminal corpora determining aqueductal stenosis and obstructive triventricular hydrocephalus. First, to restore CSF circulation, we performed an endoscopic third-ventriculostomy without lesion's biopsy, since there was normal brain tissue within the third ventricle and the tumor. Tumoral marker values were in the average range, so surgery was planned to remove the tumor. The patient, after the positioning of external lumbar drainage, underwent an occipital posterior interhemispheric retrocallosal transtentorial approach, which represents a direct surgical corridor to quadrigeminal cistern and quadrigeminal plate. Arachnoidal dissection of mesencephalic cistern and cutting of the tentorium are mandatory to obtain adequate exposure of quadrigeminal region, control over vascular structures, and lesser brain retraction. Identification of anatomical components and relationships between quadrigeminal plate with vein of Galen, PCA branches, tentorium, and medial occipital veins represents a crucial point. When this approach is selected, the venous anatomy must be navigated with caution. Angiography's venous phase may provide additional planning information.6 Coagulation of vascular structures such as occipital veins is carefully avoided since it creates risk of venous infarction, leading to visual loss. Histologic examination revealed a rosette-forming glioneuronal tumor (grade I WHO 20217).