In Reply: Optimizing Endoscopic Approaches for Sphenoid Lateral Recess Cerebrospinal Fluid Leaks: Proposal of a New Algorithm

To the Editor: We sincerely thank the authors for their insightful comments on our manuscript, “Optimizing Endoscopic Approaches for Sphenoid Lateral Recess Cerebrospinal Fluid Leaks: Proposal of a New Algorithm.”1,2 We appreciate their careful appraisal of our work and their valuable contributions to the understanding of lateral sphenoid encephaloceles. We are grateful for the opportunity to clarify and elaborate on the points raised in their letter to editor, in light of their prior publication, particularly regarding our proposed classification system and treatment algorithm. ON THE OMISSION OF ENCEPHALOCELES ENLARGING THE FORAMEN ROTUNDUM We acknowledge the authors previously published four-tier classification system and its validation in a multicenter cohort. Our proposed schema was not intended to diminish the importance of encephaloceles enlarging the foramen rotundum (FR), but rather to simplify surgical decision-making based on practical intraoperative corridors. In our experience, lesions passing through and enlarging the FR often behave surgically in a manner similar to lesions located lateral to the FR, particularly with respect to the exposure required, potential risk to maxillary division of trigeminal nerve (V2), and the possible need for Vidian nerve manipulation. For this reason, we grouped these lesions within the broader “lateral” category rather than assigning a separate subtype. We agree that FR-enlarging lesions represent a distinct radiological pattern. However, our classification was designed primarily to guide surgical corridor selection, rather than to focus solely on anatomic morphology, which may explain the structural differences between the 2 systems. ON THE DEFINITION OF “FAR LATERAL” LESIONS We appreciate the concern regarding objectivity. Our distinction between Type 3 (lateral) and Type 4 (far lateral) lesions was intended to be based on measurable radiological parameters rather than a subjective spatial impression. In Type 3 defects, the lesion lies just lateral to V2, with no bone between the FR and the defect. These defects may often be addressed with less extensive surgical approaches. By contrast, Type 4 (far lateral) defects demonstrate a clear bony separation between the V2 canal and the defect, and their management may require more extensive exposure, such as a classical transpterygoid approach. Importantly, the distance between V2 and the Vidian canal may assist in determining the feasibility of less invasive approaches. Within our proposed algorithm: A V2-Vidian distance >4 mm was associated with increased feasibility of modified transpterygoid and precaruncular approaches. A shorter distance may increase the likelihood of requiring sacrifice of the Vidian or palatine nerves. Thus, the designation “far lateral” in our framework reflects surgical accessibility relative to neurovascular anatomy, rather than simply geometric distance from the FR. We agree that further studies assessing interobserver reliability would be valuable, and we would welcome future multicenter collaboration to evaluate the reproducibility of this measurement-based approach. ON THE PRECARUNCULAR APPROACH We would like to clarify that the contralateral precaruncular approach was presented as a potential option in select anatomic situations, supported primarily by cadaveric studies. We fully agree that clinical validation is essential before any new approach can be widely adopted. Our intention was not to advocate routine use of this technique, but rather to propose a possible strategy within an algorithmic framework. Traditionally and ethically, proposing a novel surgical approach demands work and research in cadaveric models. We agree that clinical outcome data are necessary, and we are currently evaluating this approach prospectively (Figure 1A-1C).FIGURE 1.: A case of a left-sided type 4 LR cerebrospinal fluid leak with a VVD distance >4 mm, managed using a right precaruncular approach. A, Computed tomography coronal section illustrating the left type 4 LR cerebrospinal fluid leak. B, Intraoperative exposure of the defect after right-sided posterior ethmoidectomy and sphenoidotomy with intersphenoidal septum drill-out. The arrow indicates the left-sided LR filled with a meningocele. C, Visualization of the LR defect was achieved via the right precaruncular approach, preserving the left V2 branch and Vidian nerve. LR, lateral recess of sphenoid sinus; LT, left; Rt, right; V2, maxillary division of trigeminal nerve; VVD, V2- vidian distance.ON ALTERNATIVE SURGICAL APPROACHES We appreciate the authors' work describing the lateral transorbital approach, which represents an important contribution to the management of challenging lateral lesions. At the time our study was developed, the literature on transorbital neuroendoscopic surgery was still evolving, which explains why this approach was not incorporated into our original algorithm. More recent work has highlighted its potential role, particularly for lesions lateral to the FR, including certain Type 4 defects with a V2-Vidian distance less than 4 mm, where an endonasal approach may carry a higher risk to V2 or the Vidian nerve. Our ongoing prospective work (clinical not cadaveric) examining selection between precaruncular and transorbital approaches within the framework of our proposed algorithm suggests that the precaruncular approach may represent a less invasive alternative in selected cases (we have not published this data as yet). In this context, the V2-Vidian distance appears to play an important role in surgical decision-making (Figure 2A and 2B).FIGURE 2.: A case of idiopathic intracranial hypertension involving a left-sided type 2 LR cerebrospinal fluid leak and type 2 and 4 defects on the right side, with a VVD distance exceeding 4 mm. Management involved a right-sided transorbital approach due to the complex nature of the defects, alongside a left endonasal transsphenoidal approach. A, Computed tomography coronal section illustrating bilateral LR cerebrospinal fluid leaks. B, Repair of the LR roof using fat graft covered with SURGICEL medial to the temporal dura through transorbital corridor. LR, lateral recess of sphenoid sinus; VVD, V2- vidian distance.Our algorithm was not intended to exclude transorbital strategies, but rather to provide a structured decision-making pathway based on measurable radiological parameters. We believe that multiple minimally invasive corridors may be complementary within an individualized surgical strategy. CLARIFICATION OF INTENT Our proposed classification was developed with 3 main objectives: Radiological measurability. Correlation with surgical corridor selection. Minimization of unnecessary neurovascular sacrifice. It was not intended to replace existing systems, but rather to provide an additional framework that may help guide surgical decision-making as endoscopic skull base techniques continue to evolve. Differences between classification systems may reflect differing priorities, such as anatomic description vs operative planning, and we believe these perspectives can be complementary.