MONITORING OF CENTRAL NERVOUS SYSTEM FUNCTIONS

Abstract

Central nervous system monitors fall into two main groups. Those that monitor functional end points and those which monitor oxygen supply to the brain.

The functional monitors which have been used are the awake - up test, electroencephalogram (EEG) and evoked potentials (EPs). Xenon measurement of cerebral blood flow, doppler assessment of flow velocity, jugular venous oxygen content and near infrared spectroscopy (NIRS) monitor oxygen supply indirectly.

The electroencephalogram (EEG) represents the on-going spontaneous - electrical activity to the brain. Signals recorded from the scalp consist of

shitling dipole fields, which are generated by the graded summation of excitatory and inhibitory potentials in cortical neurons. Bispectral index scale which is the monitor collects raw EEG data from a small electrode placed over the forehea? and temporal area. The raw data undergo bispectral analysis and other processed EEG parameters.

Evoked potentials (EPs) are the electrophysiological response of the nervous system to sensory, electrical, magnetic, or cognitive stimulation. They reflect the functional integrity of structures from which potentials arise and of pathways traversed between the site of stimulation and the neural generators of the evoked electrophysiological activity.

The most commonly used mode of evoked potentials are as follow

. (I. Somatosensory evoked potential (SSEP