Neuromodulation for the Sphenopalatine Ganglion-a Narrative Review

PURPOSE OF REVIEW

To provide an integrated overview of the current state of knowledge of neuromodulation for the sphenopalatine ganglion (SPG) by reviewing relevant and significant literature.

RECENT FINDINGS

There are several case reports and clinical trials evaluating neuromodulation for the SPG. We identified two blinded, randomized clinical trials for patients with chronic cluster headache. The randomized trials and additional studies demonstrated the long-term safety, efficacy, and cost-effectiveness of neuromodulation for the SPG. Recent studies in Europe and the USA suggest that SPG neuromodulation is a novel modality with clinical importance for treating acute cluster headaches and reducing the frequency of attacks.

Comparing The Effects of Botulinum toxin-A and multiple surgical parasympathectomy on treatment of allergic rhinitis

OBJECTIVE

Allergic rhinitis (AR) is a common disease with a recent increasing in prevalence. Traditional treatment strategies of AR, sometimes, show limited effectiveness and side effects. Intranasal injection of Botulinum toxin type A (BTX-A) and multiple postganglionic parasympathectomy of pterygopalatine ganglion (PPG) are among the increasingly used alternative treatment options of AR. In this study, we compared the early efficacy of BTX-A and multiple surgical parasympathectomy (MSP) on treatment of uncontrolled AR.

METHODS

Sixty patients who were diagnosed with uncontrolled AR, were recruited to the study. Participants randomly underwent either intranasal injection of BTX-A (45 IU in each nostril) (Group A) or bilateral MSP (Group B). All patients were evaluated in terms of nasal hypersecretions, congestion and sneezing with visual analogue scale prior to treatment and at weeks 1, 2, 4, 8, 12 and 6 months during the follow-up period.

RESULTS

A significant difference in the degree of nasal hypersecretions and sneezing could be identified in both groups before and after the interventions. Although the significant efficacy on sneezing was documented in group A and B only in the first 4 and 8 weeks, respectively, such efficacy on nasal hypersecretions extended for 12 weeks in group A and throughout the follow-up period in group B. Nasal congestion did not differ significantly in both groups.

CONCLUSION

Both BTX-A and MSP, in patients with uncontrolled AR, may be a long-lasting therapeutic option for the treatment of nasal hypersecretions, but not as effective as for sneezing and nasal congestion.

CT-Guided Thermocoagulation of the Pterygopalatine Ganglion for Refractory Trigeminal Autonomic Cephalalgia

INTRODUCTION

Trigeminal autonomic cephalalgia (TAC) is a type of one-sided cerebral painful headache, with attacks regularly accompanied by autonomic responses, such as tearing, runny nose, panic, nausea and vomiting on the affected side. Currently, the most common treatment strategies are drugs, nerve grafts and surgery. Clinical understanding of TACs is limited. Here, we report the case of thermocoagulation treatment of the pterygopalatine ganglion in an uncommon TAC under local anesthesia.

CASE PRESENTATION

A rare case of TAC was treated with computed tomography (CT)-guided thermocoagulation within the pterygopalatine ganglion. Pain and autonomic signs were relieved immediately after surgery, with the patent retaining only slight numbness on the left side of the face. This numbness completely resolved at 6 months of follow-up and there was no recurrence.

DISCUSSION

Trigeminal autonomic cephalalgia seriously affects the patient's quality of life, but clinical understanding is limited. In the case reported here, we performed CT-guided thermocoagulation of the pterygopalatine ganglion at 90 °C for 180 s for treatment of a trigeminal autonomic headache. To our knowledge, this is the first report of using thermocoagulation at 90 °C to treat the pterygopalatine ganglion. We found that this strategy results in fewer side effects and is a more cost-effective treatment for such patients than other options.

CONCLUSION

Computed tomography-guided thermocoagulation of the pterygopalatine ganglion at 90 °C for 180 s for treatment of trigeminal autonomic headache is a safe and economical treatment option.

Neural control of choroidal blood flow

The choroid is richly innervated by parasympathetic, sympathetic and trigeminal sensory nerve fibers that regulate choroidal blood flow in birds and mammals, and presumably other vertebrate classes as well. The parasympathetic innervation has been shown to vasodilate and increase choroidal blood flow, the sympathetic input has been shown to vasoconstrict and decrease choroidal blood flow, and the sensory input has been shown to both convey pain and thermal information centrally and act locally to vasodilate and increase choroidal blood flow. As the choroid lies behind the retina and cannot respond readily to retinal metabolic signals, its innervation is important for adjustments in flow required by either retinal activity, by fluctuations in the systemic blood pressure driving choroidal perfusion, and possibly by retinal temperature. The former two appear to be mediated by the sympathetic and parasympathetic nervous systems, via central circuits responsive to retinal activity and systemic blood pressure, but adjustments for ocular perfusion pressure also appear to be influenced by local autoregulatory myogenic mechanisms. Adaptive choroidal responses to temperature may be mediated by trigeminal sensory fibers. Impairments in the neural control of choroidal blood flow occur with aging, and various ocular or systemic diseases such as glaucoma, age-related macular degeneration (AMD), hypertension, and diabetes, and may contribute to retinal pathology and dysfunction in these conditions, or in the case of AMD be a precondition. The present manuscript reviews findings in birds and mammals that contribute to the above-summarized understanding of the roles of the autonomic and sensory innervation of the choroid in controlling choroidal blood flow, and in the importance of such regulation for maintaining retinal health.

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 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.

Depicting the pterygopalatine ganglion on 3 Tesla magnetic resonance images

PURPOSE

The pterygopalatine ganglion has yet not been identified on medical images in living humans. The primary aim of this study was to evaluate whether the pterygopalatine ganglion could be identified on 3 T MR imaging.

METHODS

This study was performed on medical images of 20 Caucasian subjects on both sides (n = 40 ganglia) with an exploratory design. 3 T MR images were assessed by two physicians for the presence and size of the pterygopalatine ganglion. The distance from the pterygopalatine ganglion to four bony landmarks was registered from fused MR and CT images. In an equivalence analysis, the distances were compared to those obtained in an anatomical cadaveric study serving as historical controls (n = 50).

RESULTS

A structure assumed to be the pterygopalatine ganglion was identified on MR images in all patients on both sides by both physicians. The mean size was depth 2.1 ± 0.5 mm, width 4.2 ± 1.1 mm and height 5.1 ± 1.4 mm, which is in accordance with formerly published data. Equivalence of the measurements on MR images and the historical controls was established, suggesting that the structure identified on the MR images is the pterygopalatine ganglion.

CONCLUSION

Our findings suggest that the pterygopalatine ganglion can be detected on 3 T MR images. Identification of the pterygopalatine ganglion may be important for image-guided interventions targeting the pterygopalatine ganglion, and has the potential to increase the efficacy, safety and reliability for these treatments.