Cluster headache: crosspoint between otologists and neurologists—treatment of the sphenopalatine ganglion and systematic review

Among cephalgias, cluster headache (CH) is the rarest and the most disabling, explaining the appellation of “suicide headache.” Up to 20% of chronic CH reveals to be resistant to pharmacological treatments, in which case interventional procedures should be considered. Many reports evaluated invasive approaches and a wide strand of research is dedicated to the sphenopalatine ganglion. Our paper will now be focused on providing an overview on modern applications on the sphenopalatine ganglion (SPG), their outcomes, and their feasibility in terms of risks and benefits. The group reviewed the international literature systematically for procedures targeting the sphenopalatine ganglion and its branches for episodic and chronic CH, including block, stimulation, radiofrequency, stereotactic radiosurgery, and vidian neurectomy. Seventeen articles fixed our inclusion criteria. Comparing the outcomes that have been analyzed, it is possible to notice how the most successful procedure for the treatment of refractory chronic and episodic CH is the SPG block, which reaches respectively 76.5% and 87% of efficacy. Radiofrequency has a wide range of outcomes, from 33 to 70.3% in CCH. Stimulation of SPG only achieved up to 55% of outcomes in significant reduction in attack frequency in CCH and 71% in ECH. Radiosurgery and vidian neurectomy on SPG have also been analyzed. Generally, ECH patients show better response to standard medical therapies; nevertheless, even this more manageable condition may sometimes benefit from interventional therapies mostly reserved for CCH. First results seem promising and considering the low frequency of side effects or complications, we should think of expanding the indications of the procedures also to those conditions. Outcomes certainly suggest that further studies are necessary in order to understand which method is the most effective and with less side effects. Placebo-controlled studies would be pivotal, and tight collaboration between neurologists and otorhinolaryngologists should also be central in order to give correct indications, which allow us to expect procedures on the SPG to be an effective and mostly safe method to control either refractory ECH or CCH.