Topographic sleep EEG changes in the acute and chronic stage of hemispheric stroke ROSITSA PORYAZOVA 1 , RETO HUBER 2 , RAMIN KHATAMI 1,3 , ESTHER WERTH 1 , PETER BRUGGER 1 , KRIZSTINA BARATH 4 , CHRISTIAN R. BAUMANN 1 and CLAUDIO L. BASSETTI 1,5 1 Department of Neurology, University Hospital Zurich, Zurich, Switzerland, 2 University Children’s Hospital Zurich, Zurich, Switzerland, 3 Sleep Centre, Clinic Barmelweid, Barmelweid, Switzerland, 4 Department of Neuroradiology, University Hospital Zurich, Zurich, Switzerland, 5 Department of Neurology, Inselspital, Bern, Switzerland Keywords delta activity, slow-wave activity, spindle frequency range, stroke recovery, synaptic plasticity, theta activity Correspondence Rositsa Poryazova, MD, Department of Neurology, University Hospital Zurich, Frauenklinikstrasse 26, CH-8091 Zurich, Switzerland. Tel.: +41 44 255 1111; fax: +41 44 255 4380; e-mail: rositsa.poryazova@usz.ch Accepted in revised form 28 June 2014 ; received 26 March 2014 DOI: 10.1111/jsr.12208 SUMMARY After stroke, the injured brain undergoes extensive reorganization and reconnection. Sleep may play a role in synaptic plasticity underlying stroke recovery. To test this hypothesis, we investigated topographic sleep electroencephalographic characteristics, as a measure of brain reorganization, in the acute and chronic stages after hemispheric stroke. We studied eight patients with unilateral stroke in the supply territory of the middle cerebral artery and eight matched controls. All subjects underwent a detailed clinical examination including assessment of stroke severity, sleep habits and disturbances, anxiety and depression, and high-density electroencephalogram examination with 128 electrodes during sleep. The recordings were performed within 10 days after stroke in all patients, and in six patients also 3 months later. During sleep, we found higher slow-wave and theta activity over the affected hemisphere in the infarct area in the acute and chronic stage of stroke. Slow-wave, theta activity and spindle frequency range power over the affected hemisphere were lower in comparison to the non-affected side in a peri- infarct area in the patients’ group, which persisted over time. Conversely, in wakefulness, only an increase of delta, theta activity and a slowing of alpha activity over the infarct area were found. Sleep slow-wave activity correlated with stroke severity and outcome. Stroke might have differ- ential effects on the generation of delta activity in wakefulness and sleep slow waves (1–8 Hz). Sleep electroencephalogram changes over both the affected and non-affected hemispheres reflect the acute dysfunction caused by stroke and the plastic changes underlying its recovery. Moreover, these changes correlate with stroke severity and outcome. INTRODUCTION Ischaemic stroke is caused by the interruption of blood supply to the brain. This results in insufficient oxygen and glucose delivery, and disrupts cellular homeostasis. In turn, multiple processes leading to cell death and subsequent neuronal reorganization are triggered. Sleep–wake disturbances and changes are common after stroke. In patients with hemispheric stroke, changes in sleep architecture and reduced sleep quality have been reported (Bassetti and Aldrich, 2001; Giubilei et al., 1992; Gottselig et al., 2002; Hachinski et al., 1979; Muller et al., 2002). Additionally, changes in sleep electroencephalogram (EEG) waveforms as sleep spindles (12–15 Hz) and slow waves (0.5–4.5 Hz) have been described (Gottselig et al., 2002). In the course of recovery after stroke, recovery of sleep quality and sleep parameters occurs (Gottselig et al., 2002; Vock et al., 2002). Moreover, sleep EEG parameters are linked to stroke severity and outcome (Bassetti and Aldrich, 2001; Gottselig et al., 2002; Muller et al., 2002; Vock et al., 2002). It is conceivable that changes in sleep parameters would depend on stroke location. Striatal and cortical strokes in mice cause different patterns of sleep changes (Baumann et al., 2006). Additionally, sleep manipulation is much easier to ª 2014 European Sleep Research Society 1 J Sleep Res. (2014) Regular Research Paper