Background: Pontine cavernous malformations (CM) located on a peripheral pontine surface or the fourth ventricular floor are resectable lesions, but those deep within the pons away from a pial surface are typically observed. However, the anterior bulge of the pons formed by the brachium pontis creates a unique entry point for access to deep pontine lesions from below, working upwards through the pontomedullary sulcus (PMS).
Objective: We developed a transpontomedullary sulcus (TPMS) approach to these lesions.
Methods: The TPMS approach used the far lateral craniotomy and upper vagoaccessory triangle to define the surgical corridor. The entry point was above the olive, lateral to the pyramidal tracts and cranial nerve (CN) 6, above the pre-olivary sulcus and CN 12, and medial to CN 7/8 and CN9/10/11.
Results: Four patients underwent this approach. All presented with hemorrhage and CN 6 palsies. All pontine CMs were resected completely. Three patients were improved or unchanged, with good outcomes (mRS <= 2) in all patients.
Conclusion: The central pons remains difficult territory to access, and new surgical corridors are needed. The bulging underbelly of the pons allows access to pontine lesions deep to the pial surface from below. The far lateral-TPMS approach is a novel and more direct alternative to the retrosigmoid trans-middle cerebellar peduncle approach. Unlike the retrosigmoid approach, the TPMS approach requires minimal parenchymal transgression and uses a brainstem entry point medial to most lower cranial nerves. Favorable results demonstrate the feasibility of resecting pontine CMs that might have been previously deemed unresectable.
From: The Far Lateral-Transpontomedullary Sulcus Approach to Pontine Cavernous Malformations: Technical Report and Surgical Results by Abla, et al.