Measurement and implications of the distance between the sphenopalatine ganglion and nasal mucosa: a neuroimaging study

Abstract Background Historical reports describe the sphenopalatine ganglion (SPG) as positioned directly under the nasal mucosa. This is the basis for the topical intranasal administration of local anaesthetic (LA) towards the sphenopalatine foramen (SPF) which is hypothesized to diffuse a distance as short as 1 mm. Nonetheless, the SPG is located in the sphenopalatine fossa, encapsulated in connective tissue, surrounded by fat tissue and separated from the nasal cavity by a bony wall. The sphenopalatine fossa communicates with the nasal cavity through the SPF, which contains neurovascular structures packed with connective tissue and is covered by mucosa in the nasal cavity. Endoscopically the SPF does not appear open. It has hitherto not been demonstrated that LA reaches the SPG using this approach. Methods Our group has previously identified the SPG on 3 T–MRI images merged with CT. This enabled us to measure the distance from the SPG to the nasal mucosa covering the SPF in 20 Caucasian subjects on both sides (n = 40 ganglia). This distance was measured by two physicians. Interobserver variability was evaluated using the intraclass correlation coefficient (ICC). Results The mean distance from the SPG to the closest point of the nasal cavity directly over the mucosa covering the SPF was 6.77 mm (SD 1.75; range, 4.00–11.60). The interobserver variability was excellent (ICC 0.978; 95% CI: 0.939–0.990, p < 0.001). Conclusions The distance between the SPG and nasal mucosa over the SPF is longer than previously assumed. These results challenge the assumption that the intranasal topical application of LA close to the SPF can passively diffuse to the SPG

Measurement and implications of the distance between the sphenopalatine ganglion and nasal mucosa: a neuroimaging study

Background Historical reports describe the sphenopalatine ganglion (SPG) as positioned directly under the nasal mucosa. This is the basis for the topical intranasal administration of local anaesthetic (LA) towards the sphenopalatine foramen (SPF) which is hypothesized to diffuse a distance as short as 1mm. Nonetheless, the SPG is located in the sphenopalatine fossa, encapsulated in connective tissue, surrounded by fat tissue and separated from the nasal cavity by a bony wall. The sphenopalatine fossa communicates with the nasal cavity through the SPF, which contains neurovascular structures packed with connective tissue and is covered by mucosa in the nasal cavity. Endoscopically the SPF does not appear open. It has hitherto not been demonstrated that LA reaches the SPG using this approach. Methods Our group has previously identified the SPG on 3T-MRI images merged with CT. This enabled us to measure the distance from the SPG to the nasal mucosa covering the SPF in 20 Caucasian subjects on both sides (n=40 ganglia). This distance was measured by two physicians. Interobserver variability was evaluated using the intraclass correlation coefficient (ICC). Results The mean distance from the SPG to the closest point of the nasal cavity directly over the mucosa covering the SPF was 6.77 mm (SD 1.75; range, 4.00-11.60). The interobserver variability was excellent (ICC 0.978; 95% CI: 0.939-0.990, p<0.001). Conclusions The distance between the SPG and nasal mucosa over the SPF is longer than previously assumed. These results challenge the assumption that the intranasal topical application of LA close to the SPF can passively diffuse to the SPG

OnabotulinumtoxinA injection towards the SPG for treating symptoms of refractory chronic rhinosinusitis with nasal polyposis: a pilot study

Background and objective The main objective of this prospective, open, uncontrolled pilot study was to investigate the safety of administering onabotulinumtoxinA (BTA) towards the sphenopalatine ganglion (SPG) in 10 patients with refractory chronic rhinosinusitis with nasal polyposis (CRSwNP) using a novel injection tool, the MultiGuide®. Material and methods A one-month baseline period was followed by bilateral injections of 25 U BTA in the SPG and a follow-up of 12 weeks. The primary outcome was adverse events (AE), and the main efficacy outcome was a 50% reduction in visual analogue scale (VAS) symptoms for nasal obstruction and rhinorrhea in months 2 and 3 post-treatment compared to baseline. Results We registered 13 AEs, none of which were serious, however, one patient experienced diplopia which moderately affected his daily activities. The symptoms slowly improved and resolved 4 weeks after injection. Five patients were treatment responders with at least 50% median reduction in the nasal obstruction, and four were treatment responders concerning rhinorrhea. Conclusions Injection of BTA toward the SPG using the MultiGuide® in patients with CRSwNP appears to be safe but with a potential for moderately disabling side effects. The study indicates a beneficial effect on nasal obstruction