Abstract

Background: Gonyautoxin are phycotoxins, whose molecular mechanism of action is a reversible block of the voltage-gated sodium channels at axonal level, impeding nerve impulse propagation. Objective: To evaluate clinical efficacy of gonyautoxin in the treatment of patients with chronic tensional-type headache. Methods: Open trial from September 2004 to 2005 in Hospital Clínico Universidad de Chile. Twenty-seven patients with chronic tension-type headache were locally infiltrated with gonyautoxins (50 micrograms) in ten sites considered as pain trigger points in a fixed infiltration protocol. In each site, a volume of 200 microlitres was injected. EMG recording was performed before and immediately after infiltrations. Main outcome measures are where a significantly drop-off in acute headache pain score occurs and number of days without headache pain. Results: No side effects were detected in the follow-up period. From base line of 2 weeks, 19 patients of 27 (70%) are the successfully responders to the treatment. They showed the remarkable immediate effect after infiltration demonstrated by trapezium EMG recording. Patients reported a fall in pain score 5 minutes post-injection from 5.0 ± 2.8 to 1.6 ± 1.6 (mean ± SD). The responder showed an average of 8.1 ± 9.9 weeks of headache pain-free, all of them without a second infiltration or use of any additional analgesic medication. Discussion: The therapeutic properties of gonyautoxin local infiltration in chronic tension-type headache patients are shown to be safe and effective. This report describes a new therapy for chronic tension-type headache involving local infiltrations of gonyautoxins. The immediate headache pain relief effect shown only minutes after toxin infiltrations were the most remarkable feature of this protocol. This is the first gonyautoxins testing report in the treatment of chronic tension-type headache. © 2009 W. S. Maney & Son Ltd.