Cortical sensorimotor alterations in Unverricht-Lundborg disease patients without generalized seizures

We investigated cortical functions of two Unverricht-Lundborg disease (ULD) patients suffering from myoclonic jerks, but no generalized tonic-clonic seizures. Somatosensory cortical responses were recorded to median nerve stimuli and coherence was calculated between cortical and muscle signals during isometric contraction of hand muscle. In contrast to ULD patients with generalized tonic-clonic seizures, responses of the primary somatosensory (SI) cortex were only slightly enhanced in the left and normal in the right hemisphere, and no early responses were observed in the ipsilateral SI. Cortex-muscle coherence was remarkably enhanced. We conclude that in ULD patients without generalized tonic-clonic seizures, both the excitability of the SI and transcallosal conduction are relatively normal, probably decreasing susceptibility to generalized seizures. Disturbed cortical control of muscle contraction indicates selective alteration of the motor cortex activation.