Real-Time Ultrasound Navigation Technique for a Transmiddle Cerebellar Peduncle Approach for Resection of Pontine Cavernous Malformation: 2-Dimensional Operative Video.

Brainstem cavernous malformations are rare, potentially neurologically devastating lesions. Microsurgical resection remains the gold-standard in the treatment of these lesions, and its goals consist of (1) complete resection of the malformation and (2) avoidance of new permanent neurological deficits. Resection should be carefully considered in patients who have accessible symptomatic lesions. We present the case of a 63-year-old man who presented with a pontine hemorrhage secondary to an inferior central pontine cavernous malformation, which rebled during his inpatient stay. He had significant cranial nerve deficits, and therefore, surgery was recommended, and the patient consented to the procedure. The lesion was approached by an extended retrosigmoid craniotomy and transmiddle cerebellar peduncle safe entry zone. A real-time ultrasound navigation technique was used to guide the intraparenchymal portion of the procedure. For this technique, a cottonoid patty was used as a fiducial for the brainstem surface and allows for accurate localization of the malformation as well as for determining the adequate intraparenchymal dissection trajectory. The hematoma was evacuated, and the malformation was resected in piecemeal fashion. An endoscope was used to assist with inspection of the brainstem cavity. The patient did well postoperatively. MRI revealed complete resection of the malformation and evacuation of the hematoma as well as evidencing the surgical trajectory. Intraoperative ultrasound is a strikingly helpful tool for localization of the malformation as well as trajectory planning and may be more reliable than stereotactic navigation, given accuracy concerns in the posterior fossa and within the deep parenchyma of the brainstem.