Microanatomy of the neural scaffold of the pterygopalatine fossa in humans: trigeminovascular projections and trigeminal-autonomic plexuses.

The pterygopalatine fossa (PPF) is an anatomically-hidden deep extracranial space. The neural scaffold of the PPF remains anatomically understudied in humans. Moreover, there are no anatomical data in humans pointing out the extracranial trigeminovascular distributions, in contrast to the trigeminal supratentorial ones. By anatomical microdissections, the neural scaffold of the PPF and the presence of trigeminovascular projections were evaluated. The anterior and superior approaches of the pterygopalatine fossae in nine dissected blocks of human middle skull base and the frontal cuts of two different specimens, led to several results: (1) the neurovascular contents of the PPF, embedded in the pterygopalatine adipose body, have a layered disposition; (2) the posterior neural layer is represented by a pterygopalatine cross, centred by the pterygopalatine ganglion (PPG) that sends off ascending, descending, and medial branches and has a lateral connection with the maxillary nerve - 4 quadrants could have been defined as referring to this cross; (3) at the level of the upper lateral quadrant there are two superposed layers (i) a superficial plexus contributed by the maxillary nerve, the maxillary artery plexus and the PPG and its orbital branches (OBs) and (ii) a deep layer, consisting of the OBs proper of the PPG; (4) within the PPF and on the posterior wall of the maxillary sinus distinctive trigeminovascular projections were evidenced. The anastomoses involving autonomic and trigeminal fibres, located in the PPF passage to the orbital apex, support the complicate and polymorphous neural input to the orbit, while the evidence of a pterygopalatine trigeminovascular scaffold offers a substrate for a better understanding of various facial algias.