EEG features and epilepsy in MECP2-mutated patients with the Zappella variant of Rett syndrome

ObjectiveTo assess the presence/absence of peculiar EEG features and epilepsy in MECP2-mutated Rett patients with the Zappella–Rett variant (Z-RTT) also known as preserved speech variant.MethodsRetrospective analysis of 16 (age 19.4 ± 8.4 years; range 8–38 years) MECP2 mutated Z-RTT cases, including 11 high or intermediate performance (HIP), and five low-performance (LP) patients was performed. Peculiar EEG features were analyzed as a function of the HIP or LP Z-RTT categories: (1) centro-temporal spikes, (2) multifocal EEG activity, (3) EEG encephalopathy (i.e. multifocal EEG activity associated with the presence of background slowing and diffuse slow activity), (4) spindles and K-complex. Furthermore, we assessed the occurrence of epilepsy.Correlations between electroclinical features and category of Z-RTT genotype (missense or truncation mutation) were also tested.ResultsThe Z-RTT HIP group showed a very abnormal EEG (presence of centro-temporal spikes: p = 0.004808), although the cases studied were not epileptogenic and did not develop encephalopathy. The LP group showed multifocal EEG activity (p = 0.000229), EEG encephalopathy (p = 0.000229) and epilepsy (p = 0.299451). No significant differences between the prevalence of centro-temporal spikes, multifocal EEG activity, EEG encephalopathy, and epilepsy between the patients with the truncation or missense mutation were observed.ConclusionsEEG electrophysiological patterns and epileptogenic susceptibility differ in Z-RTT according to the level of performance (i.e. HIP or LP).SignificanceThese results indicate that HIP and LP Z-RTT should be considered as distinct entities, not only on a clinical basis, but also as it concerns EEG features and epileptogenic susceptibility.These results could offer support in the practical management of patients and family counseling.