Anatomical and clinical appraisal of the pterygopalatine ganglion

Abstract

The anatomy of the pterygopalatine ganglion (PPG) and its branches is related to pain syndromes Cluster headache (CH) and Sluder’s neuralgia (SN). In order to gain more insight in these syndromes, we conducted an anatomical and clinical study of the PPG. A search for new neural structures in the PPF was performed through microdissection of human cadaveric PPF whole-mount preparations. A hitherto unknown nerve, which runs between the PPG and the ophthalmic nerve, was identified in all specimens. The nerve was classified as an orbital PPG branch, and may explain pain relief in the ophthalmic area after PPG blockage. Immunohistochemical techniques were used to characterize PPG branches, specifically orbital branches. Four PPF specimens were cryosectioned as a whole. In one specimen, the recently discovered neural structures were separately cryosectioned. Sections were stained for general, sympathetic and parasympathetic neural markers. The recently discovered orbital PPG branch is of a parasympathetic and sensory nature. In other orbital PPG branches, sympathetic fibres were demonstrated as well. This knowledge may add to understanding the symptomatology of facial pain and its therapy. The radiological anatomy of the PPF and its contents were described using magnetic resonance imaging at 7 Tesla (7T MRI). A human cadaveric PPF specimen was examined on 7 T MRI, and subsequently cryosectioned. MR images were compared with corresponding surface photos and on-tape collections of cryosections. 7T MRI provided excellent depiction of specifically smaller structures, that have previously been obscured. 7T MRI may provide an improved diagnostic and preoperative evaluation of the PPF. The clinical part of this thesis starts with a systematic review of SN literature. Based on the described symptoms, distinct SN criteria were formulated, which enable its recognition as a separate clinical entity. Considering its symptomatology, SN could possibly be a trigeminal autonomic cephalalgia. The effects of radiofrequency thermocoagulation (RFT) of the PPG on facial pain are described, following critical evaluation of diagnosis. We conducted a retrospective study of the clinical records of patients who underwent RFT of the PPG at a tertiary clinic. Diagnoses were re-evaluated after which the effect of RFT on facial pain was assessed. Seven patients out of fifteen had been diagnosed correctly. Nine out of fifteen patients showed pain relief after RFT. Positive results were present among patients with Sluder’s neuropathy, atypical facial pain and CH. Hence, correct facial pain diagnosis is vital to assess the outcome of treatment strategies. The effects of microvascular decompression (MVD) of the PPG are described in three refractory CH patients. The pterygopalatine artery was ligated and a temporal muscle graft was placed between the artery and the ganglion. No differences were found between the pre and postsurgical period with respect to pain and quality of life. These data suggest that MVD of the PPG does not provide pain reduction or improvement of quality of life in patients with refractory CH. Recommendations for future research may include studies regarding pathophysiology and treatment on larger cohorts of SN patients, and further study on unexplained aspects of CH pathophysiology