Sleep slow-wave homeostasis and cognitive functioning in children with electrical status epilepticus in sleep.

STUDY OBJECTIVES: Encephalopathy with electrical status epilepticus in sleep (ESES) is characterized by non-rapid eye movement (non-REM)-sleep-induced epileptiform activity and acquired cognitive deficits. The synaptic homeostasis hypothesis describes the process of daytime synaptic potentiation balanced by synaptic downscaling in non-REM-sleep and is considered crucial to retain an efficient cortical network. We aimed to study the overnight decline of slow waves, an indirect marker of synaptic downscaling, in patients with ESES and explore whether altered downscaling relates to neurodevelopmental and behavioral problems. METHODS: Retrospective study of patients with ESES with at least one whole-night electroencephalogram (EEG) and neuropsychological assessment (NPA) within 4 months. Slow waves in the first and last hour of non-REM-sleep were analyzed. Differences in slow-wave slope (SWS) and overnight slope course between the epileptic focus and non-focus electrodes and relations to neurodevelopment and behavior were analyzed. RESULTS: A total of 29 patients with 44 EEG ~ NPA combinations were included. Mean SWS decreased from 357 to 327 µV/s (-8%, p < 0.001) across the night and the overnight decrease was less pronounced in epileptic focus than in non-focus electrodes (-5.6% vs. -8.7%, p = 0.003). We found no relation between SWS and neurodevelopmental test results in cross-sectional and longitudinal analyses. Patients with behavioral problems showed less SWS decline than patients without and the difference was most striking in the epileptic focus (-0.9% vs. -8.8%, p = 0.006). CONCLUSIONS: Slow-wave homeostasis-a marker of synaptic homeostasis-is disturbed by epileptiform activity in ESES. Behavioral problems, but not neurodevelopmental test results, were related to severity of this disturbance.

Specific EEG markers in POLG1 Alpers' syndrome.

OBJECTIVE: To examine whether rhythmic high-amplitude delta with superimposed (poly)spikes (RHADS) in EEG allow a reliable early diagnosis of Alpers-Huttenlocher syndrome (AHS) and contribute to recognition of this disease. METHODS: EEGs of nine patients with DNA-proven AHS and fifty age-matched patients with status epilepticus were retrospectively examined by experts for the presence of RHADS and for accompanying clinical signs and high-frequency ripples. Reproducibility of RHADS identification was tested in a blinded panel. RESULTS: Expert defined RHADS were found in at least one EEG of all AHS patients and none of the control group. RHADS were present at first status epilepticus in six AHS patients (67%). Sometimes they appeared 5-10 weeks later and disappeared over time. RHADS were symptomatic in three AHS patients and five AHS patients showed distinct ripples on the (poly)spikes of RHADS. Independent RHADS identification by the blinded panel resulted in a sensitivity of 87.5% (95% CI 47-100) and a specificity of 87.5% (95% CI 77-94) as compared to the experts' reporting. CONCLUSION: RHADS are a highly specific EEG phenomenon for diagnosis of AHS and can be reliably recognized. Clinical expression and EEG ripples suggest that they signify an epileptic phenomenon. SIGNIFICANCE: RHADS provide a specific tool for AHS diagnosis.