Recording sleep and wake

As well as in all medical disorders, taking the patient's history is very important in sleep medicine, too. Polygraphic studies, however, are indispensable and recording of sleep and wake gets a more and more important role in clinical neurophysiology. This chapter is meant to give an overview of technical aspects, how to perform recording and to give an estimate of the diagnostic yield of poly(somno)graphy. Choices are pointed out instead of rigid rules. The text aims at providing outlines that can serve to choose ways of performing polysomnography. To make such choices one should realize what may be encountered in sleep medicine. Thus, insight into the classi®cation of sleep and wake disorders is necessary before registration is started (Table 1). Polygraphy should be taken in the strict sense of the word. That means not only recording of signals related to clinical neurophysiology as EEG and EMG but also parameters from other ®elds, for example pulmonary physiology. There are several possibilities for recording sleep. The most extensive but also very expensive and time consuming way is polysomnography in the laboratory, in fact the `gold standard'. Another possibility is polysomnography at home using portable recorders. Both methods give insight in many parameters of sleep. Polysomnography at home can easily be extended to daytime recording and provides data not only on sleep but on wakefulness, naps etc. as well. Finally, there is limited polygraphy with one to four channels of recording of various parameters, often respiration or movements. Standardized methods to measure wakefulness are the Multiple Sleep Latency (MSLT) and the Maintenance of Wakefulness (MWT) tests. As there are many combinations of what can be recorded (see Table 2), the concept of `modules' is introduced here. A module is a way of recording signals related to sleep and wake de®ned by the method used, for example EEG, EMG, EOG, ECG, thermistor recording of respiration, etc. It is the aim of this chapter to describe possibilities and give advise how to perform recording of sleep and wake. Still, one can make his own `mix of modules' to get the ideal recording for that particular patient and during given circumstances. Each module will be described in technical details (Section 2) and most used combination of modules (Section 3). Rules for assessment and the relative 159 Recommendations for the Practice of Clinical Neurophysiology: Guidelines of the International Federation of Clinical Physiology (EEG Suppl. 52) Editors: G. Deuschl and A. Eisen q 1999 International Federation of Clinical Neurophysiology. All rights reserved. Published by Elsevier Science B.V.