Electrophysiological monitoring in neurosurgical patients with increased intracranial pressure

Abstract

There is considerable evidence that changes in common electrophysiologic recordings, such as those of sensory evoked potentials, do not provide reliable information about changes in intracranial pressure (ICP). Several studies in animals (Bothe et al., 1993) as well as in human (Konasiewicz et al., 1994; Moulton et al., 1994) have shown that changes in sensory evoked potentials (somatosensory evoked potentials (SSEP), brainstem auditory evoked potentials (BAEP), or visual evoked potentials (VEP) are poorly correlated with changes (elevation) in ICP. Some studies, in which sensory evoked potentials were recorded simultaneously with ICP, have shown that sometimes an elevated ICP does not affect neural function but sometimes it is accompanied by changes in sensory evoked potentials, thus an indication of altered neural function. Only when an elevated ICP affects neural function as a result of ischemia or other forms of injury to neural tissue (perhaps deformation of brain tissue) are there consistent changes in specific evoked potentials (Moulton et al., 1994). There is experimental evidence that changes in sensory evoked potentials are closely related to changes (decrease) in arteriovenous oxygen content (AVDO₂) (Moulton et al., 1994), which is a sign of a decrease in cerebral oxygenation. Thus an elevated ICP does not seem to play a direct role in the deterioration of neural function.