The Lance-Adams syndrome (LAS) is a disabling chronic post-hypoxic action/intention myoclonus occurring days or weeks after a brain hypoxic event. Its treatment mainly relies on antiseizures and antimyoclonic medications with a poor efficiency. We report the striking observation of myoclonus improvement following spontaneous epileptic seizures in a patient with a severe refractory LAS. The action myclonus decreased during a few days after each generalized seizure. To reproduce seizures and to relieve the myoclonus, we performed recurrent electroconsulvive therapy (ECT). While ECT did not have side effects, it has a strong efficacy to decrease the myoclonic jerks allowing her to stand, walk, wash, and eat alone. We thereafter report the evolution of the Unified Myoclonus Rating Scale (UMRS), a validated clinical rating instrument that measures the severity and intensity of myoclonus in various modes. We also provide arguments that the action myoclonus originate from the neocortex, based on scalp EEG recording and polygraphic EMG recording with EEG jerk-locked back averaging. To our knowledge, this is the first report of effectiveness of ECT in LAS. This case may open minds for the use of non-invasive neuromodulation techniques in LAS. Moreover, the positive effect of ECT in this patient may pave the way for further clinical and preclinical research concerning the still unknown pathophysiological mechanisms of myoclonus in LAS.