Exoscopic En Bloc Total Petrosectomy for Temporal Bone Carcinomas, Technical Aspects, and Application in Three Cases

Introduction: Temporal bone carcinomas represent therapeutic challenges with high rates of residual and recurrent disease unless radical resection can be achieved. Radical surgical excision with clean margins is the ultimate therapeutic goal and results in better prognosis and survival rates. En bloc total petrosectomy with negative margins has been to shown to correlate with improved outcomes. Introduction of extracorporeal video microscopy AKA exoscopes to neurosurgical practice can potentially enhance visibility through a wider field of view and facilitate digital image enhancement, which decreases the need of continuous manipulation and adjustment required during microscopic surgery.

Methods: (Anatomical study) Two embalmed and latex injected head specimens were prepared using standardized techniques. The skin incision is centered on the ear. A neck dissection was performed along the anterior border of the sternocleidomastoid muscle exposing the ICA and IJV. A frontotemporal craniotomy was performed, followed by a pretemporal transcavernous interdural exposure. Osteotomies were performed by high-speed drilling to separate the cone shaped petrous bone with its apex medially directed. The first cut was made by drilling the sigmoid sinus plate from the asterion downward and medially to the jugular bulb, followed by dissection of the dura from the posterior petrous surface until the dural covering of the 7th and 8th nerves entered the IAC, where both nerves are sacrificed. The second cut was made along the lateral wall of the carotid canal. The third (medial) cut was performed in the posteromedial triangle of the anterior petrous apex as described by Kawase et al. A final small cut was made connecting the distal end of the second cut to the quadrilateral space created by the Kawase approach, posteromedial to V3. The large defect resulting after the en bloc resection requires sufficient reconstruction with a vascularized free flap. Surgical technique: Three patients presenting with complete 7th and 8th cranial nerve dysfunction secondary to invasive carcinomas were identified and underwent an en bloc resection utilizing the technique described above. General anesthesia was induced in a standard fashion, patients were placed supine with reversed Trendelenburg and the head tilted 90 degrees. Cerebral relaxation was achieved with mannitol, dexamethasone, and hyperventilation. Resection proceeded as described under exoscopic visualization utilizing the Storz 3D Vitom exoscope and a Uni-arm exoscope holder. Reconstruction was done with vascularized free flaps in all cases.

Results: The cadaveric study confirmed the feasibility of the technique as illustrated. Working corridors achieved provided ample exposure with early proximal and distal vascular control. All three patients experience no intraoperative or postoperative complications. Postoperative imaging showed gross-total resection of the lesions and pathological examination revealed clean margins in the en bloc specimens in all cases. Follow-up range (4–12 months), one patient died of unrelated cardiac cause, other two alive with no recurrence.

Conclusion: En bloc total petrosectomy for invasive temporal bone carcinomas is safe and resulted in gross-total resection with negative margins in three patients. This technique requires further evaluation in a larger patient sample with long-term follow-up to determine its true efficacy.

No conflict of interest has been declared by the author(s).