Long-term effectiveness of sphenopalatine ganglion stimulation for cluster headache

Abstract

Objectives The sphenopalatine ganglion (SPG) plays a pivotal role in cluster headache (CH) pathophysiology as the major efferent parasympathetic relay. We evaluated the long-term effectiveness of SPG stimulation in medically refractory, chronic CH patients. Methods Thirty-three patients were enrolled in an open-label follow-up study of the original Pathway CH-1 study, and participated through 24 months post-insertion of a microstimulator. Response to therapy was defined as acute effectiveness in ≥ 50% of attacks or a ≥ 50% reduction in attack frequency versus baseline. Results In total, 5956 attacks (180.5 ± 344.8, range 2-1581 per patient) were evaluated. At 24 months, 45% ( n = 15) of patients were acute responders. Among acute responders, a total of 4340 attacks had been treated, and in 78% of these, effective therapy was achieved using only SPG stimulation (relief from moderate or greater pain or freedom from mild pain or greater). A frequency response was observed in 33% ( n = 11) of patients with a mean reduction of attack frequency of 83% versus baseline. In total, 61% (20/33) of all patients were either acute or frequency responders or both. The majority maintained their therapeutic response through the 24-month evaluation. Conclusions In the population of disabled, medically refractory chronic CH patients treated in this study, SPG stimulation is an effective acute therapy in 45% of patients, offering sustained effectiveness over 24 months of observation. In addition, a maintained, clinically relevant reduction of attack frequency was observed in a third of patients. These long-term data provide support for the use of SPG stimulation for disabled patients and should be considered after medical treatments fail, are not tolerated or are inconvenient for the patients.

Keywords: Cluster headache; long-term effectiveness; neuromodulation; neurostimulation; sphenopalatine ganglion.

Figure 1.

Pathway CH-1 study chart.

Figure 2.

Patient disposition from the Pathway CH-1 and extended follow-up studies.

Figure 3.

Effective therapy for all patients (n = 33 patients). Acute responses to sphenopalatine ganglion stimulation in 5956 cluster attacks. Percentages of attacks achieving effective therapy at the evaluation point (including both pain freedom and pain relief) are given for all evaluable attacks from the open-label phase through to the 24-month study visit.

Figure 4.

Numbers of attacks treated with sphenopalatine ganglion stimulation and acute effectiveness are shown for each patient. In addition, acute responders are identified with a *.

Figure 5.

Attack frequencies at baseline and at 24 months are shown for each patient. Eleven patients were attack frequency responders, nine experienced clinically insignificant changes (< 50% change in either direction) and 11 experienced increases in attack frequency of at least 50%. Acute responders are identified with a *.

Figure 6.

At 24 months, 61% (20/33) had a therapeutic response, defined as either an acute and/or frequency response of at least 50%, and of these, 65% (13/20) had a very strong (≥75%) response to therapy. More than 80% (27/33) of patients experienced a response of at least 30%.

Figure 7.

Therapeutic response to therapy defined as an acute and/or frequency response is consistent over time. At each time point, each square represents an individual patient. Responders are further categorised as acute (a), frequency (f) or both (b). Dotted borders indicate changes in response. The majority of patients maintained a response to therapy, with two patients gaining and three patients losing response between each of the time points evaluated.