Early detection of vasospasm after acute subarachnoid hemorrhage using continuous EEG ICU monitoring

The Utility of EEG, SSEP, and Other Neurophysiologic Tools to Guide Neurocritical Care

“…Ratios may adjust for artifacts, which increase power in multiple frequency ranges and magnify the effect of transitions from faster alpha frequencies within health brain tissue to slower delta rhythms following ischemia, transitions to sleep, or in the intra-ictal and post-ictal states. This data may be averaged over a duration of time or depicted without averaging to permit visual inspection of alpha power variability, for example [110].…”

“…Initial experience with quantitative EEG suggested that total power provides high sensitivity exceeding 90% for ischemia following subarachnoid hemorrhage [108]. Quantitative EEG variables, such as relative alpha variability trend of total power and post-stimulation alphadelta ratio (ADR) may be used as an early warning system to detect slowing and loss of fast activity, reflective of focal ischemia in an early timeframe before it is clinically apparent in SAH patients with predominantly good-or poor-grade SAH [109,110]. In SAH patients with depressed level of arousal or coma, such as Hunt-Hess grade IV or V patients, a decline in ADR during periods of arousal has been associated with the development of delayed cerebral ischemia.…”

Quantitative EEG for the Detection of Brain Ischemia

“…qEEG and xenon CT measures of CBF were used simultaneously in 32 awake SAH patients (Hunt-Hess 1-3) to detect vasospasm, which was confi rmed by angiography or TCD [8]. Th e relative alpha percentage, defi ned uniquely as 6-14 Hz frequency power divided by the total power (1-20 Hz), was calculated over 2 minute windows to generate a histogram periodically throughout the day.…”

“…Serial neurological exams and imaging are only capable of detecting delayed cerebral ischemia once the damage becomes clinically or radiographically apparent. In this case, EEG may be a useful way to detect and subsequently treat ischemia before the injury becomes irreversible [7][8][9][10].…”

Can Quantitative EEG Reliably Predict Deterioration from Delayed Cerebral Ischemia Secondary to Vasospasm?

“…Actually, with decreasing perfusion sequential EEG changes are observed while brain tissue initially is in a state of reversible and then later irreversible brain injury [16]. A number of quantitative EEG parameters have been shown to correlate with DCI and vasospasm after SAH [17,18] and may indicate this secondary complication up to 2 days prior to other tests [17]. However, all of these prior studies were conducted in an artificial study setting, which is one of the reasons that this technique is not widely used.…”