Sleep in right hemispherectomized patients: evidence of electrophysiological compensation

Objectives. The goal of this study is to provide a better understanding of the role of the cortex in sleep's macro- and microstructure modulation. Methods: Sleep architecture and phasic events were investigated in 4 patien ts having undergone right functional or anatomical hemispherectomy and 8 co ntrol subjects. Between-groups differences were assessed using the Wilcoxon -Mann-Whitney test. Results: Findings provide evidence for overall similarity between patients' and control subjects' left hemispheric sleep architecture. In addition, re sults clearly indicate that it is possible to detect electrical activity ov er the operated side of a hemispherectomized patient's brain, even when res ection of the hemi-cortex has been complete. Finally, findings provide evid ence for similar left and right hemispheric relative spectral activities an d for an increase in fast activity bands over the intact hemisphere in anat omical hemispherectomized patients. Conclusions: This study provides evidence that right hemispherectomy does n ot produce significant sleep architecture alterations as recorded over the intact hemisphere. In addition, residual activity detected over the operate d side in anatomical hemispherectomized patients is interpreted as resultin g from volume conduction originating from generators located in the intact hemisphere. Finally, there is strong evidence for electrophysiological comp ensation in the intact hemisphere following complete resection of the contr alateral hemi-cortex. (C) 2000 Elsevier Science Ireland Ltd. All rights res erved.