We report on a case of polymicrogyria with benign childhood epilepsy and amyotrophic lateral sclerosis (ALS). While performing dexterity tasks with either hand, strong unsustained mirror movements of the unintended hand were observed. The patient was seen over a period of three years and, as often seen in ALS, there was a moderate progress of the motor neuron disease affecting the upper and lower motor neuron in an asymmetrical manner. In addition, more rapidly progressive bulbar symptoms could be observed by the clinical and neurophysiological examination. MRI revealed polymicrogyria of the right frontal lobe with irregular bumpy inner and outer surface and abnormally thick and smooth cortex, dysplastic insular cortex and asymmetrically widened Sylvial fissure. No signs of atrophy, especially of the motorcortex and corticospinal tract were observed. The corpus callosum was completely developed and of normal size. We hypothesize an enrolment of the dysplastic right frontal lobe pathophysiology of the observed mirror movements.