Gonyautoxin are phycotoxins, whose molecular mechanism of action is a reversible block of the voltage-gated sodium channels at neuronal level. They are axonal conduction blockers impeding nerve impulse propagation. In order to evaluate the clinical efficacy of Gonyautoxin 2/3 epimers in the treatment of patients diagnosed with chronic tensional-type headache, the patients were locally injected with placebo versus Gonyautoxin following a painful spots injection standarized protocol