<jats:p> Glutaric aciduria type 1 is an autosomal recessive disorder caused by deficiency of glutaryl-coenzyme A dehydrogenase, with accumulation of glutaric acid, 3-hydroxyglutaric acid and glutaconic acid. Increased blood glutarylcarnitine levels are the basis for identification of affected infants by newborn screening. Despite the highly variability, this disease usually presents with an acute encephalitis-like encephalopathy in infancy or childhood after a period of normal development. The characteristic neurological sequel is a complex movement disorder due to acute bilateral striatal injury. Frequently, the only abnormality preceding the first episode is a progressive macrocephaly. Although neuroimaging findings are quite variable, the widening of the Sylvian fissures combined with abnormalities of the basal ganglia in a child with macrocephaly should raise the suspicion of this diagnosis. We describe two patients in whom macrocephaly was the only presenting symptom and whose diagnosis was suggested by the brain MRI findings. Our purpose is to illustrate the clinical value of neuroimaging in the diagnosis of glutaric aciduria type 1 even before the onset of neurologic symptoms, which is particularly important if newborn screening is not available.