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

OBJECTIVE: To 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. METHODS: Retrospective analysis of 16 (age 19.4+/-8.4years; range 8-38years) 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. RESULTS: The 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. CONCLUSIONS: EEG electrophysiological patterns and epileptogenic susceptibility differ in Z-RTT according to the level of performance (i.e. HIP or LP). SIGNIFICANCE: These 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.

Drug-resistant epilepsy and epileptic phenotype-EEG association in MECP2 mutated Rett syndrome.

OBJECTIVE: To determine in MECP2-mutated Rett syndrome (RTT [MIM 312750]): (1) the prevalence of drug-resistant epilepsy (DRE); (2) whether the presence of DRE is related to the abnormal EEG patterns or to the particular MECP2 mutant genotype. METHODS: Retrospective survey of a large population of patients (n=154) evaluated between 1978 to 2007 (May) at the Child Psychiatry and Neurology Unit of Siena (Italy) with both clinical and genetic (i.e. MECP2 mutated) diagnoses of RTT. Some subjects were followed for up to 20 years. Among those, cases with epilepsy were first selected for study; within that group, cases with DRE were identified and studied. The association between clinical severity of their epilepsy and quantitative or qualitative scores of EEG severity was tested using rank coefficients (Spearman's rho values). The relationship between DRE and RTT genotype category (i.e. gene deletion, gene duplication, early truncating mutation, late truncating mutation, and missense mutation) or a specific MECP2 genotype was tested using the chi-square test. A p-value <0.05 (two sided) was considered to indicate statistical significance. RESULTS: Prevalence of DRE was 16% (i.e. 16 DRE out of 100 MECP2-mutated RTT epileptic patients). No significant relationship was found between clinical severity of DRE and quantitative (p=0.9190) or qualitative EEG scores (p=0.1511). In addition, no significant relationship was found between the DRE and the RTT genotype category (chi-square=1.147, DF=4, p=0.8867), or a specific MECP2 genotype (chi-square=30.958, DF=39, p=0.8173). CONCLUSIONS: Although RTT MECP2-mutated patients suffer from a serious and progressive encephalopathy, it is "epileptogenic" but not "DREgenic" as they have a decreased risk (16%) for DRE compared to the general epileptic population (DRE: 20-40%). The presence of DRE is not related to abnormal EEG findings or a particular MECP2 mutant genotype. SIGNIFICANCE: These observations could be of help in the practical management and family counseling.

Myoclonic encephalopathy in the CDKL5 gene mutation.

OBJECTIVE: Epilepsy with mutation of the CDKL5 gene causes early seizures and is a variant of Rett syndrome (MIM (312750), which is reported typically as infantile spasms. The purpose of this study was to analyze the epileptic histories and EEGs of patients with the CDKL5 mutation. METHODS: We reviewed the epilepsy histories and electroclinical analyses of three girls aged 9.5, 7.4, and 9.4 years, each with a mutation of the CDKL5 gene. RESULTS: We revealed the presence of an encephalopathy that started by 1.5 months of age. At first, seizures involved tonic spasms or complex partial seizures, and were complicated by the later appearance of complex partial, tonic, and unexpectedly, myoclonic seizures. This form of epilepsy was drug resistant. Routine and prolonged video EEGs both displayed a homogeneous electroclinical pattern consisting of (a) unique background with diffuse high voltage sharp waves of 6-7 Hz, and absence of the typical rhythmic frontal-central theta activity present in Rett syndrome; (b) unique awake and sleep background, with diffuse, high voltage, continuous sharp waves with multifocal and diffuse spikes; (c) rhythmic, diffuse, 15 Hz activity accompanied clinically by tonic seizures; (d) intercritical pattern with pseudoperiodic, diffuse, sharp waves or pseudoperiodic, diffuse spike and polyspike or wave discharges; and (e) diffuse, spike, polyspike and wave discharges accompanied by massive or focal myoclonias or both. CONCLUSIONS: Patients with the CDKL5 mutation have an early onset, epileptic encephalopathy in infancy that evolves into myoclonic seizures in childhood with a unique EEG pattern. SIGNIFICANCE: Recognizing this type of encephalopathy could be useful in prompting clinicians to proceed further with their diagnostic work in patients not fitting the criteria of classical Rett syndrome.