The Role of Endoscopy for Resection of Hypoglossal Schwannomas: An Illustrative Case Report

Hypoglossal schwannomas are a rare clinical entity. These lesions tend to present at a later stage with tongue atrophy. For intracranial lesions, a far lateral transcondylar approach is an accepted surgical approach. For lesions with extracranial extension, a neck exploration is warranted. In patients with both intracranial and cervical extension, surgical resection would require both treatment avenues. Despite a craniocervical exposure, visualization of portions of the tumor can be difficult. We present such a case and the use of an endoscope to aid in resection.

Case Presentation: A 25-year-old woman presented with an enlarging neck mass. Examination revealed tongue atrophy and a palpable neck mass. Imaging revealed evidence of a large tumor with a cervical component displacing the carotid artery and intracranial extension, with remodeling of the ipsilateral occipital condyle, expansion of the hypoglossal canal, extension into the clivus and extension into the CP angle, abutting the intracranial vertebral artery.

Surgical Case: The patient was placed in a standard lateral position with head secured in pins to allow for a far lateral transcondylar approach. The incision was planned in continuity with the separate neck dissection portion of the surgery. Initially, the cervical portion of the tumor was dissected and followed through as much as possible to the base of the skull. The far lateral transcondylar craniotomy was then performed. The tumor was meticulously dissected off the lower cranial nerves and the vertebral artery. The intracranial intradural component of the tumor was resected. The dural border was then opened laterally to continue resection of extradural tumor in the hypoglossal canal and clivus. Using a microscope, most of the tumor appeared to have been resected. An endoscope was employed to gain a near 360 degree appreciation of the regional anatomy. A large residual extradural component of the tumor was noted and resected with endoscopic guidance. The endoscope allowed visualization of the superior limit of the cervical exposure, confirming a gross total resection. The hypoglossal canal was then plugged with muscle, a dural substitute and fibrin glue. Hemostasis was obtained and the incision closed in standard fashion. The patient was monitored in the intensive care unit for 24 hours. An MRI confirmed a gross total resection. The patient had a transient mild dysphagia that resolved within a few days. Overall, the patient remained neurologically unchanged from prior surgery.

Conclusion: A hypoglossal schwannoma with significant extra and intracranial extension needed a combined neck dissection with a far lateral transcondylar craniotomy. Once maximum viewing of the intracranial portion was obtained, an endoscope provided invaluable information of the remainder of the tumor burden not afforded by traditional means. We attempt to highlight the improved visibility and more thorough tumor resection achieved with the addition of an endoscope. Further experience with transcranial endoscope utilization is warranted.