Electrophysiological monitoring of neurological functions at the acute phase of brain injury

Abstract

The continuous monitoring of physiological parameters is now considered as a standard of care in intensive care units (ICU). While multiple techniques are available to guide hemodynamic or respiratory management, the monitoring of neurological function in unconscious patients is usually limited to discontinuous bedside neurological examination or morphological brain imaging. However, cortical activity is accessible at the bedside with electroencephalography (EEG), electrocorticography (ECoG) or evoked potentials. The analysis of the unprocessed signal requires a trained neurophysiologist and could be time consuming. During the past decades, advances in neurophysiological signal acquisition make it possible to calculate quantified EEG parameters in real-time. New monitors also provide ICU friendly display for a dynamic and live assessment of neurological function changes. In this review, we will describe the technical aspects of EEG, ECoG and evoked potentials required for a good signal quality before interpretation. We will discuss how to use those electrophysiological techniques in the ICU to assess neurological function in comatose patients at the acute phase of brain injuries such as traumatic brain injuries, haemorrhagic or ischemic stroke. We will discuss, which quantitative EEG or evoked potentials monitoring parameters can be used at the bedside to guide sedation, evaluate neurological function during awaking and look for new neurological (encephalic or brainstem) injuries. We will present the state of the art and discuss some analyses, which may develop shortly.