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In 1963, J.W. Lance and R.D. Adams firstly described their four patients who developed myoclonus after cardiopulmonary arrest. Myoclonus was stimulated by active muscular contraction, therefore it was called action or intention myoclonus (Lance-Adams syndrome).13 Auditory stimuli, tactile stimuli, passive/active movement, coordination or anxiety can trigger myoclonus.13–16 Patients may develop negative myoclonus (postural lapses) concomitantly with positive myoclonus.17 Chronic PAM develops days to weeks after hypoxic events. Cerebellar dysfunction, such as gait ataxia, dysmetria, slurred speech, usually coexists with myoclonic movement. Unlike acute PAM, patients with chronic PAM must regain consciousness following hypoxic events.3,15 Chronic PAM is more likely caused by respiratory arrest, such as acute asthmatic attack, than cardiac arrest.9,14,15 Pathophysiology Acute PAM The pathophysiology of acute PAM is not well understood. Acute post-anoxic myoclonus can be caused by either cortical or brainstem damage.18,19 Interestingly, there was a report of spinal generated myoclonus presenting with abdominal myoclonus in a post-cardiac arrest patient.20 The various electroencephalographic (EEG) patterns were reported to correlate with myoclonic episodes including bursts of generalized synchronous spike, polyspike activity and burst suppression pattern.7,18,19 The epileptiform discharges from EEG reported in some acute PAM patients support the hypothesis that acute PAM may represent ictal phrase of epileptic seizure.7 The pathophysiology of stimulus-sensitive acute PAM remains inconclusive. However, short-lived neuronal hyperexcitability between motor cortex and posterior parietal cortex, which is a major multimodal sensory i... ... middle of paper ... ...77–9. 37. Liron L, Chambost M, Depierre P, Peillon D, Combe C. [Effectiveness of valproic acid for postanoxic action myoclonus (Lance-Adams syndrome)]. Ann. Fr. Anesth. Reanim. 1998;17(10):1247–9. 38. Carroll WM, Walsh PJ. Functional independence in post-anoxic myoclonus: contribution of L-5-HTP sodium valproate and clonazepam. Br. Med. J. 1978;2(6152):1612. 39. Rollinson RD, Gilligan BS. Postanoxic action myoclonus (Lance-Adams syndrome) responding to valproate. Arch. Neurol. 1979;36(1):44–5. 40. Thal LJ, Sharpless NS, Wolfson L, Katzman R. Treatment of myoclonus with L-5-hydroxytryptophan and carbidopa: clinical, electrophysiological, and biochemical observations. Ann. Neurol. 1980;7(6):570–6. 41. Budhram A, Lipson D, Nesathurai S, Harvey D, Rathbone MP. Postanoxic Myoclonus: Two Case Presentations and Review of Medical Management. Arch. Phys. Med. Rehabil. 2013.

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