A Computerized Tomographic and Cadaveric Study of Sphenopalatine Ganglion Block Via the Pterygomaxillary Fissure: Anatomical Considerations of the Suprazygomatic Approach

Background: The sphenopalatine ganglion (SPG) is a parasympathetic ganglion that’s implicated in multiple primary headache disorders. Current techniques are inconsistent or require imaging. A suprazygomatic approach is thought to be safe and effective. The main objectives are to determine an accurate depth and needle angulation to perform SPG blocks safely and effectively.Methods: Cranial computerized tomography was obtained from 40 Caucasians (20 male, 20 female). For each patient, a line is drawn from the frontozygomatic angle to the pterygomaxillary fissure (PMF) to represent length. Intersection of the line in both transverse and coronal Frankfurt planes create inferior and posterior angulations, respectively.A cadaver dissection is performed to validate the needle placement utilizing these measurements. Contrast fluoroscopy is utilized to verify needle placement in PMF.Results: The mean length was 24.9 +/- 2.8mm for males and 23.8 +/- 0.5mm for females. The difference was statistically significant (p = .019). In patients younger than 40 years, the mean length was 24.5 +/- 2.8mm. In patients greater than 40 years, the mean length was 26.1 +/- 3.1mm. The difference was statistically significant (p = .018). Both inferior and posterior angles were not statistically different between sex or age. Post-contrast imaging confirmed presence of dye in the PMF.Conclusion: While there is a difference in depth between sex and age groups, it’s likely not clinically significant. A depth of 25mm angulated at 6 degrees inferior and 27 degrees posterior is likely generalizable. Bony landmark-based, suprazygomatic SPG blocks via the PMF are probably feasible, safe with minimal risk and may be an option in special patient populations and/or circumstances.