To redefine benign myoclonus of early infancy (BMEI), clinical and neurophysiologic features in 102 infants (60 male) with brief paroxysmal abnormal movements and normal neurologic and psychomotor development were studied at one center in Argentina and two in Italy. Infants with movements occurring only during sleep and those with abnormal EEG were excluded. Age at onset was 1-12 months (median 6.2 months). The nonepileptic paroxysmal motor phenomena included myoclonus in 23, brief tonic contractions and spasms in 38, shuddering in 35, atonia or ‘negative’ myoclonus in 4, and more than one motor phenomenon in 9. The movements generally involve the head and neck and upper limbs, and lower limbs are spared. EMG recordings of motor phenomena were characteristic of spasms, and associated with normal EEG. Episodes occurred only while awake in 87 (85%), both awake and asleep in 15 (15%), and were repeated several times a day, often (44% cases) in clusters. Except for 2 sisters with BMEI, no familial cases were found. Brain imaging and metabolic studies were normal. Episodes resolved at 6-30 months of age, the majority in the 2nd year. Two cases presented clinical and EEG features of benign focal epilepsy. Language and cognitive development were normal in all cases; fifteen (16%) developed hyperkinetic behavior without learning disorders. 
COMMENT. The authors conclude that the spectrum of the syndrome of BMEI is wide, each paroxysmal motor phenomenon has a characteristic EMG pattern with normal EEG, and the prognosis is benign. The syndrome is similar to that described by Lombroso CT and Fejerman N , and should be distinguished from West syndrome. A report of shuddering attacks in a 3-year-old girl found that flexion spasms without loss consciousness were controlled by propranolol . A family history of essential tremor is reported in patients with shuddering attacks and some patients have both shuddering and tremor . These authors propose that shuddering is an early manifestation of essential tremor. Intolerance to monosodium glutamate is reported in children with shuddering attacks.