Endoscopic Transnasal Approach for Resection of a Recurring Anterior Skull Base Aneurysmal Bone Cyst: A Case Report and Review of the Literature

Introduction: Aneurysmal bone cysts (ABCs) are benign, expansile, osteolytic lesions that usually affect the long bones and spinal column. Their occurrence in the skull is rare, but when present, they most commonly present in the first two decades of life. A variety of approaches currently exists for accessing anterior skull base ABCs, including transcranial approaches, subcranial-midfacial degloving approaches, and endoscopic endonasal procedures. There are few reported cases in the literature of ABCs occurring in the skull base, and the use of endoscopic techniques for their treatment is exceedingly rare. We report an anterior cranial base ABC that was successfully resected using an endoscopic transnasal approach, ameliorating the patient’s deteriorating vision.

Methods: The authors present a case of an anterior cranial base aneurysmal bone cyst (ABC) causing optic canal erosion and visual loss. The details of this case are provided, and a review of the literature was performed.

Results: A 22-year-old woman developed right eye visual loss from an anterior cranial base ABC. Radiographically, the lesion within the right sphenoid sinus was loculated with multiple fluid/fluid levels and measured 2.6 cm × 1.8 cm. The patient’s visual symptoms initially improved with an endonasal endoscopic biopsy and decompression at an outside institution 1 month prior to her presentation to our practice. One month later, the patient’s visual loss and decreased acuity returned. An MRI showed a recurrent 1.7 × 1.9 × 2.1-cm lesion extending from the right ethmoid region and over the right anterior clinoid process with encasement of the right optic nerve. Preoperative CT also demonstrated severe erosion of the adjacent cranial base and optic canal. She underwent an endoscopic transnasal approach with orbital osteotomy and extradural anterior clinoidectomy, as well as removal of the fovea ethmoidalis and sphenoidotomy. Complete resection of the ABC was achieved with full restoration of her vision.

Conclusions: Aneurysmal bone cysts involving the cranial base are rare. When symptomatic with cranial nerve compression, complete surgical resection, when possible, is necessary to prevent recurrence. Simple fenestration and decompression are likely to result in rapid recurrence of the lesion and associated symptoms as occurred in our patient and in other reports in the literature. An endoscopic endonasal approach can be utilized for the resection of cranial base ABCs with good therapeutic, cosmetic, and functional results.