A Simplified Transpterygoid Technique to Lateral Sphenoid Encephaloceles: A Shorter Run for a Longer Slide

Introduction: Encephaloceles and cerebrospinal fluids (CSF) leaks in the lateral sphenoid sinus have traditionally been difficult to repair. The originally described endoscopic transpterygoid approach affords a direct trajectory, but is burdened with an involved and time-consuming dissection of the pterygopalatine fossa (PTF) and related risks. We have developed a modified transpterygoid approach which involves a subperiosteal dissection maintain the integrity of the PTF contents retracting them inferiorly and laterally allowing access to the lateral sphenoid recess.

Methods: Patients who underwent the endoscopic modified transpterygoid-contents intact technique (EMTCIT) for lateral sphenoid recess encephaloceles at two academic centers between 2014 and 2019 were identified. Patients with any other pathologies (iatrogenic CSF leaks, skull base tumors) were not included. Patient demographics, repair techniques, and outcomes were recorded. The primary endpoint was successful repair of the CSF leak, with secondary outcomes including dry eye, bleeding, or trigeminal nerve related symptoms. The technique begins with removal of the posteromedial wall of maxillary sinus. The palatine bone is drilled and the anterior aspect of the bony sphenopalatine foramen is removed to permit mobilization of the medial aspect of the PTF contents. The sphenoid face is opened maximally in the lateral dimension. Dissection in a subperiosteal plane is performed for mobilization of the PPF contents inferiorly and laterally. This permits further bone removal of the lateral sphenoid face and pterygoid wedge, permitting access to the lateral recess. If necessary, the Vidian nerve and/or the distal aspect of the sphenopalatine artery may be sacrificed to provide further exposure. Using a 30degree endoscope with a malleable bipolar or angled coblator, the encephalocele is resected. The skull base defect is then prepared and reconstructed with free or pedicled nasal mucosal grafts.

Results: Twenty-one patients underwent the EMTCIT. The average BMI was 46.4. Skull base defects were reconstructed using free mucosal grafts in the large majority of cases (15/21). A nasoseptal flap was used in four patients and fat in two patients. There were no persistent or recurrent CSF leaks occurred for a 100% success rate. Complications included three patients with temporary V2 anesthesia that recovered (14.3%), and 1 patient with subjective eye dryness which improved over several months (4.8%). There were no cases of epistaxis or hemorrhage requiring intervention. Average follow-up was 1.1 years.

Discussion: The modified transpterygoid technique described allows for access to the lateral sphenoid sinus without exposure of the PPF contents, greatly simplifying the approach and minimizing damage to neurovascular structures. Although the exposure afforded is not a straight-line trajectory to the defect site, our results suggest that with the aid of angled endoscopes and instruments, successful management of encephaloceles in this area can be reliably performed. For more aggressive pathologies, a traditional transpterygoid approach with PTF dissection may be preferred.

Conclusion: The EMTCIT greatly simplifies exposure of the lateral sphenoid sinus for management of encephaloceles, without compromising access. This technique obviates the need for PTF dissection and should be considered for the management of benign lesions involving the lateral sphenoid sinus.