Using the Lateral Pontine Safe Entry Zone for Resection of Deep-Seated Cavernous Malformations in the Lateral Pons:...

The retrosigmoid approach is one of the main approaches used in the surgical management of pontine cavernous malformations. It definitely provides a lateral route to large central lesions but also makes possible resection of some ventral lesions as an alternative to the petrosal approaches. However, when these vascular malformations do not emerge on surface, one of the safe corridors delimited by the origin of the trigeminal nerve and the seventh-eight cranial nerve complex can be used.1-5  Baghai et al2 described the lateral pontine safe entry zone in 1982, as an alternative to approaches through the floor of the fourth ventricle when performing tumor biopsies. They advocated a small neurotomy performed right between the emergence of the trigeminal nerve and the facial-vestibulocochlear cranial nerves complex. Accurate image guidance, intraoperative cranial nerve monitoring, and comprehensive anatomical knowledge are critical for this approach.4,5  Knowing the natural history of a brainstem cavernous malformation after bleeding,6 we sought to demonstrate in this video: (1) the use of the retrosigmoid craniotomy in lateral decubitus for resection of deep-seated pontine cavernous malformations; (2) the wide opening of arachnoid membranes and dissection of the superior petrosal vein complex to improve surgical freedom and prevent use of fixed cerebellar retraction; and (3) the opening of the petrosal fissure and exposure of the lateral pontine zone for gross total resection of a cavernous malformation in a 19-yr-old female with a classical crossed brainstem syndrome. She had full neurological recovery after 3 mo of follow-up.  The patient consented in full to the surgical procedure and publication of the video and manuscript.