Low frequency mu-like activity characterizes cortical rhythms in epilepsy due to ring chromosome 20

OBJECTIVES: To evaluate the spectral and spatial features of the cortical rhythms in patients affected by ring chromosome 20 - [r(20)]-syndrome. METHODS: Twelve patients with [r(20)] syndrome were studied. As controls we enrolled 12 patients with idiopathic generalized epilepsy (IGE) and 12 healthy volunteers (HV). Blind source separation, spectral analyses and source reconstruction were applied in all cases in order to identify reliable spatio-temporal patterns of cortical activity. RESULTS: A theta-delta EEG rhythm was identified in [r(20)] patients, with spectral peak ranging between 3 and 7Hz and whose generators mapped over the sensory-motor cortices. A second peak laying at a frequency about double with respect to the first one was present in 6 cases. Analogue methodological approach in HV and IGE groups failed to show similar findings. CONCLUSIONS: EEG of [r(20)] patients reveals the existence of a highly reproducible EEG pattern arising from the sensory-motor system. SIGNIFICANCE: The recognition of this peculiar EEG pattern could help the diagnostic work-up. Additionally, our findings supports the existence of a parallelism between this EEG trait and the physiological "mu" rhythm which is generate by the sensory-motor system. Such link suggests a sensory-motor system dysfunction in [r(20)] patients.