INTRODUCTION: The aim of this dissertation was to investigate four minimally invasive approaches to the pterygopalatine fossa. We sought to determine which ultrasound-guided approach carries the lowest risk of maxillary artery injury and to examine the differences in injectate spread along the nerves within the pterygopalatine fossa between the palpation-guided transoral approach through the greater palatine canal and the ultrasound-guided approach via the pterygomaxillary fissure.METHODS: The study was conducted in two parts. In the first part, we analyzed and determined the trajectories (range of approach options) for the suprazygomatic as well as the anterior and posterior infrazygomatic ultrasound-guided approaches on computed tomography angiographies of cerebral arteries. The range of approach options was defined by a solid angle. Based on the trajectories in relation to bony structures and the maxillary artery, we further defined feasibility and safety. In the second part, anatomical dissections were performed on thirteen donated cadaveric heads to evaluate the distribution of injectate (methylene blue and iodinated contrast) within the pterygopalatine fossa following injections performed either via palpation through the greater palatine canal or via the posterior infrazygomatic ultrasound-guided approach.RESULTS: In the first part, we analyzed 100 computed tomographies bilaterally, resulting in 200 approach simulations. Both infrazygomatic approaches were feasible in all cases, while the suprazygomatic approach was feasible in 96.5% of cases; in the remaining cases, anatomical variants of the sphenoid bone prevented feasibility. The anterior infrazygomatic approach was safe in about one-third of cases, the posterior infrazygomatic approach in approximately three-quarters, and the suprazygomatic approach in all cases. The widest range of approach options (largest solid angle) was observed with the posterior infrazygomatic approach, while the narrowest was seen with the anterior infrazygomatic approach. In the second part, anatomical dissection after the posterior infrazygomatic approach showed methylene blue surrounding the maxillary artery, Vidian nerve, sphenopalatine ganglion, and lateral pterygoid muscle, while the iodinated contrast was predominantly found along the needle track. In one case, an injury to the temporal branch of the facial nerve was documented, and in another, an injury to the pterygoid portion of the maxillary artery. In one specimen, methylene blue extended up to the foramen rotundum, though no intracranial spread was observed. Dissection following the transoral approach through the greater palatine canal revealed methylene blue within the canal, lateral pterygoid muscle, and in the vicinity of the maxillary artery, while iodinated contrast predominantly followed the needle path in the canal and lateral pterygoid muscle. In one case, the needle perforated the posterior pterygoid plate, resulting in the entire injectate being deposited into the medial pterygoid muscle.CONCLUSION: The suprazygomatic approach, analyzed in the first part of the study, proved to be the safest in relation to the trajectory of the maxillary artery; however, its feasibility was limited due to anatomical variations of the sphenoid bone. The posterior infrazygomatic approach provided the greatest range of needle entry options and carried a moderate risk of maxillary artery puncture. It demonstrated wider injectate distribution with greater involvement of neurovascular structures, but also carried a higher risk of injury. The transoral approach was more selective and targeted, associated with lower risk of injury, but resulted in a more limited staining pattern, primarily affecting neural structures in the inferior portion of the pterygopalatine fossa.
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