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

•A reliable 3–7 Hz cortical rhythm has been found in ring chromosome 20 patients arising from the sensory-motor system.•Spectral features and spatial localization of the ring 20 cortical activity suggest a parallelism with the mu rhythm.•Our methodological approach could be applied to other homogenous population of epileptic patients in order to reveal their peculiar electrical features and hence the network involved.

ObjectivesTo evaluate the spectral and spatial features of the cortical rhythms in patients affected by ring chromosome 20 – [r(20)]-syndrome.MethodsTwelve 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.ResultsA theta–delta EEG rhythm was identified in [r(20)] patients, with spectral peak ranging between 3 and 7 Hz 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.ConclusionsEEG of [r(20)] patients reveals the existence of a highly reproducible EEG pattern arising from the sensory-motor system.SignificanceThe 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.