Dorsal Perspective of Petroclival Fissure and Its Implication in Transcranial Approaches

Objective: Tumors involving the petroclival fissure (PCF) are generally regarded as one of the most formidable challenges for skull base neurosurgeons where surgical corridors are primarily hindered by critical nerves and arteries. Endonasal approaches have emerged as key alternatives but transcranial approaches remain relevant for selected cases. Transcranial skull base approaches to the PCF include anterior transpetrosal (Kawase), presigmoidal, far lateral and combined approaches. Here, we investigated dorsal perspective of petroclival fissure and its implication in selecting transcranial approaches

Methods: Twenty-eight dried-human-skulls were collected for studying bilaterally the osseous anatomy of petroclival fissure. Sixteen silicon-injected human head specimens were examined using microscopy via Kawase, presigmoid, and far lateral approaches. The anatomical features of the PCF and relevant technical nuances in each approach were investigated. Three representative cases of lesions involving the PCF for transcranial surgery were selected to illustrate the clinical application based on anatomical findings.

Results: The typical PCF is presented as a lazy L sign with a strait stroke as upper segment with an average length of 12.1 ± 1.4 mm and an oblique stroke as lower segment with an average length of 12.9 ± 2.2 mm ([Fig. 1A]). The demarcation between the upper and lower segment of PCF corresponds to the level of internal auditory canal. The PCF can be categorized into three morphologic variations according to the development of PPsb and its relationship with foramen lacerum: type A: normal development of PPsb, type B: hypodeveloped PPsb, and type C: undeveloped PPsb ([Fig. 1B]). The abducent and glossopharyngeal nerves can be regarded as the intraoperative landmarks for upper and lower segment of PCF, respectively ([Fig. 1C, D]). The upper segment of PCF was fully disclosed in Kawase approach ([Fig. 1E]), and the whole course of PCF was disclosed in presigmoidal approach ([Fig. 1F]). The PCF was barely revealed through far lateral approach due to the obstruction of posterior cranial nerve ([Fig. 1G, H]).

Conclusions: The present study provides a detailed investigation of the microsurgical anatomy of the dorsal perspective of PCF, and relevant surgical approaches and technical nuance to the PCF that may facilitate its safe exposure with a low risk of injury to adjacent neurovascular structure.

Fig. 1 Microsurgical anatomy of petroclival fissure and its implication in transcranial approaches.

Publication History

Article published online:
01 February 2023