Interpeduncular Sulcus Approach to the Posterolateral Pons.

OBJECTIVE: In this article, we describe a new safe entry point for the posterolateral pons. METHODS: To show the adjacent anatomy and measure the part of the interpeduncular sulcus that can be safely accessed, we first performed a review of the literature regarding the pons anatomy and its surgical approaches. Thereafter, 1 human cadaveric head and 15 (30 sides) human brainstems with attached cerebellums were bilaterally dissected with the fiber microdissection technique. A clinical correlation was made with an illustrative case of a dorsolateral pontine World Health Organization grade I astrocytoma. RESULTS: The safe distance for accessing the interpeduncular sulcus was found to extend from the caudal end of the lateral mesencephalic sulcus to the point at which the intrapontine segment of the trigeminal nerve crosses the interpeduncular sulcus. The mean distance was 8.2 mm (range, 7.15-8.85 mm). Our interpeduncular sulcus safe entry zone can be exposed through a paramedian infratentorial supracerebellar approach. When additional exposure is required, the superior portion of the quadrangular lobule of the cerebellar hemispheric tentorial surface can be removed. In the presented case, surgical resection of the tumor was performed achieving a gross total resection, and the patient was discharged without neurologic deficit. CONCLUSIONS: The interpeduncular sulcus safe entry zone provides an alternative direct route for treating intrinsic pathologic entities situated in the posterolateral tegmen of the pons between the superior and middle cerebellar peduncles. The surgical corridor provided by this entry point avoids most eloquent neural structures, thereby preventing surgical complications.