The pterygopalatine ganglion in humans: a morphological study

As a rule the pterygopalatine ganglion (PPG) is considered to be a single structure of the parasympathetic nervous system, associated with the maxillary nerve in the pterygopalatine fossa (PPF). A few structural studies in humans are available in the indexed references. We designed the present study of the PPG in order to provide evidence of possible variations in morphological patterns of the PPG. We performed dissections of the PPF on 20 human adult heads, using different approaches. The dissected specimens were stained with hematoxylin-eosin and silver (Bielschowsky) or prepared for immunohistochemistry for synaptophisin and neurofilament. Four morphological types of the PPG were defined macroscopically: A (10%): partitioned PPG, the upper partition receiving the vidian nerve; B (55%): single, the upper part (base) receiving the vidian nerve; C (15%): single, but the vidian nerve reaches the lower part (tip) of the ganglion; D (20%): partitioned, the lower partition receiving the vidian nerve. We propose that it may be inappropriate to invariably regard the PPG as a single morphological structure. From individual to individual the PPG may present either as a single ganglion or as a partitioned one, with distinct superior and inferior components. Nevertheless, the presence of the dispersed pterygopalatine microganglia (DPPG) evidenced by histochemistry and immunohistochemistry serves to complete an individually variable morphological pattern of a structure usually described as single. The individual variation may be the reason for failures in ablation procedures of the PPG; partitions of the PPG and/or the DPPG may functionally correlate with specific territories and targets and further tracing studies may be helpful in validating or invalidating this theory.