BACKGROUND: Pontine cavernous malformations (CMs) 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 upward through the pontomedullary sulcus.
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) VI, above the preolivary sulcus and CN XII, and medial to CNs VII and VIII and CNs IX through XI.
RESULTS: Four patients underwent this approach. All presented with hemorrhage and CN VI palsies. All pontine CMs were resected completely. Three patients were improved or unchanged, with good outcomes (modified Rankin Scale score ≤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 transmiddle cerebellar peduncle approach. Unlike the retrosigmoid approach, the TPMS approach requires minimal parenchymal transgression and uses a brainstem entry point medial to most lower CNs. Favorable results demonstrate the feasibility of resecting pontine CMs that might have been previously deemed unresectable.
ABBREVIATIONS: AICA, anterior inferior cerebellar artery
CM, cavernous malformation
CN, cranial nerve
MCP, middle cerebellar peduncle
mRS, modified Rankin Scale
PICA, posterior inferior cerebellar artery
PMS, pontomedullary sulcus
TPMS, transpontomedullary sulcus
Department of Neurological Surgery, Center for Cerebrovascular Research, University of California, San Francisco, California
Correspondence: Michael T. Lawton, MD, University of California San Francisco, Department of Neurosurgery, 505 Parnassus Avenue, M780, San Francisco CA 94143. E-mail: firstname.lastname@example.org
Received February 19, 2014
Accepted April 08, 2014