Myoclonus occurs as a result of excessive discharge from a group of neuronsthen spreads up and down the neuraxis through 1. rapidly conducting pathways as in cortical reflex myoclonus (Hallett et al 1979) 2. or slowly conducting pathways as in propriospinal myoclonus (Brown et al 1991). The spread is usually so fast that the details cannot e appreciated y the na!ed eye" necessitating neurophysiologic studies.Drugs inducing myoclonus include 1. anticon#ulsants" $ewer %&' such as lamotrigine ((ans)!y et al 2***) and gaapentin (%sconape et al 2***+ Holt!amp et al 2**,)" 2. le#odopa" %mantadine has een reported to cause cortical myoclonus (-atsunaga 2**1)" and selegiline ..Tricyclic antidepressants may cause an encephalopathy and myoclonus with &&/ changes that may e confused with Creutzfeldt-Jakob disease (0oerstl et al 1919). 2. lithium multifocal action myoclonus of cortical origin without epileptiform anormalities on routine &&/ at toxic and therapeutic doses3. 0entanyl ,. 4ropofoltransient cortical reflex myoclonus that re5uires no treatment ('earlo#e and 'earlo#e 2**2+ $immaanrat 2**3). 7. -eflo5uine" used in chloro5uine6resistant 4 falciparum malaria" caused multifocal myoclonus in one patient. ((imene)6Huete et al 2**2). 1. Tardi#e myoclonus has een descried following exposure to long6term neuroleptics (7ittle and (an!o#ic 1917). 9. car#edilol (a eta6loc!er) (0ernande) and 0riedman 1999) 1*. and antiiotics such as gatifloxacin (-arinella 2**1) ha#e een reported to induce myoclonus.Differential diagnosisThe differential diagnosis of an isolated myoclonic jerk includes 1. chorea2. and tic. .. The term myoclonic dystonia refers to a comination of myoclonus and dystonia in other muscles (8eso et al 191.). 2. Terminal !inetic tremor and cereellar ataxia may e se#ere enough to e confused with myoclonus. The two may coexist asin progressi#e myoclonic ataxia" and only after the treatment of myoclonus can the true se#erity of the underlying ataxia e appreciated. 3. 9ome patients with postural tremor may ha#e changes in amplitude" gi#ing the impression of myoclonus" ut rarely do these two conditions coexistIsolated choreic jerk choreic :er! is 1. not stimulus sensiti#e 2. and tends to e not as rapid as myoclonus. .. ;n its fully de#eloped form" chorea results in continuous random" flowing" 5uic!" and arrhythmic mo#ements. 2. 0urther" motor impersistence occurs such as inaility to !eep the tongue protruded and waxing and waning of the grip strength (mil!maid