The pathophysiology of shuddering attacks in 4 infants, ages 8 to 14 months, was studied using video-electroencephalographic monitoring, at the Epilepsy Center, Nishi-Niigata Central National Hospital, Niigata, Japan. Attacks occurred in clusters while awake, from a maximum of 5 to >100 daily, and a duration of 5-6 seconds. They included staring, straining, and shivering involving the head and upper extremities, without impairment of consciousness. Unusual movements included rare opisthotonic postures, clenching of teeth and hands, and eye deviation. Changing of diapers and being fed at meal times would often precipitate attacks. At follow-up at 25 to 45 months of age, attacks had resolved in one and occurred rarely (weekly to once every 3 months) in 3. Three were born prematurely. MRI was normal in 2, showed hypoplasia of the corpus callosum in 1, and a flattened sella turcica in 1. The EEG was normal, except for EMG contamination during attacks in 2. The EMG records had the same frequency as essential tremor. One had a positive family history of epilepsy. 
COMMENT. Shuddering attacks (SA) are an uncommon benign disorder of infants and young children, with movements resembling shivering and straining, without impaired consciousness or epileptiform EEG, and showing resolution or improvement by 2 or 3 years of age. One previous report considered SAs an early manifestation of essential tremor . They may be misdiagnosed as epilepsy.
Infantile tremor syndrome due to magnesium nutritional deficiency (Meningoencephalitic syndrome) should also be considered in differential diagnosis. This syndrome occurs in Indian infants between ages 6 months and 2 and 1/2 years and is associated with severe malnutrition. The tremor is rapid and disappears in sleep. Serum, CSF, and urine magnesium levels are decreased. Tremors respond to magnesium, but a complicating delay in psychomotor development is not corrected.