Electroencephalogram dates back more than a century, but only in the last few decades has technology afforded us the opportunity to explore the full potential of continuous EEG (cEEG). In spite of mounting evidence that continuous EEG monitoring provides vital advantages in numerous clinical settings, including for patients with status epilepticus, cerebral ischemia, disorders of consciousness and cardiac arrest, it remains a severely underutilized tool.
A December 2018 article in Neurology Today begins by stating, “A retrospective cross-sectional study found that despite the fact that continuing electroencephalography (cEEG) use was associated with lower in-hospital mortality in critically ill patients, cEEG is underutilized.” The article goes on to explore some reasons for the underutilization, concluding that the cost of equipment and lack of trained professionals to properly use it were contributory.
Fortunately, advances in both hardware and cloud-computing are reducing the major barriers to taking advantage of cEEG.
Advances in cEEG
As stated by a University of Pittsburgh study in Epilepsia, continuous EEG monitoring provides uninterrupted assessment of cerebral cortical activity with good spatial resolution and excellent temporal resolution. The procedure allows for constant assessment of brain function in critically ill and comatose patients.
Since the early 1990s, digital EEG monitoring has increased the ease with which EEG waveforms can be read. Advances in EEG displays, such as both density spectral array (DSA) and compressed spectral array (CSA), enhanced these capabilities. These visualization tools allow for trending over time, which can help clinicians to identify things like alpha-delta ratio changes (indicates vasospasm in subarachnoid hemorrhage) or allows technologists to quickly survey whether and how well a seizure medication is working in a patient seizing frequently throughout a continuous and long EEG study.
Further study in digital storage and cloud computing, as well as data transmission speed, allowing for remote monitoring and analysis, have made cEEG both more technically feasible and versatile. cEEG can now by deployed in multiple settings, such as emergency departments and in the ICU. The proliferation of broadband internet connects a network of techs and board-certified physician readers who can contribute from anywhere.
These advances in monitoring tools and access make cEEG highly useful in cases of:
- Seizures, including non-convulsive status epilepticus (NCSE)
- Intracranial hemorrhage
- Post Cardiac Arrest
- Hypoxic Ischemic brain injury and metabolic disorders in pediatric patients
Positive Clinical Results
As advances in technology break down some of the barriers to routine use of cEEG, it is valuable to look at some of the evidence in favor of continuous brain monitoring.
Obviously, mortality is an important metric for all facilities. The aforementioned Neurology Today article pointed to some telling statistics regarding the impact of cEEG on hospital mortality rates.
Another study in Neurology in Jan. 2019 concluded, “cEEG was associated with lower in-hospital mortality but used for only 0.3% of the critically ill population,” leading the abstract to conclude, “there was a >10-fold increase in cEEG use from 2004 to 2013. However, this procedure may still be underused.”
Nonconvulsive status epilepticus (NCSE) is commonly exhibited in terminally ill patients in an altered mental state. It is not uncommon for NCSE to elude diagnosis, however, because its symptoms are more subtle than convulsive status epilepticus. Continuous EEG monitoring is crucial for accurate diagnosis of NCSE.
As cEEG use in the neurocritical care setting increases, there is increasing evidence of its utility. A July 2019 article in the Journal of Intensive Care stated, “cEEG has been demonstrated to be effective in determining the response to, and outcome of, NCSE treatment.” Correct diagnosis of NCSE requires analysis of EEG patters over time, making cEEG an important method for managing this contingent of patients.
cEEG is becoming an increasingly important diagnostic tool in the Neonatal Care Unit. Among neonates followed in a 2017 study, 67% received cEEG monitoring. cEEG helped to confirm or rule out ongoing seizures in more than one-third of cases, which in turn proved the value of continuous electroencephalographic monitoring in neonates.
A Cleveland Clinic article based on a 2013 survey found cEEG to be valuable for monitoring brain function in pediatric patient with altered mental status. cEEG was critical in detecting nonconvulsive seizures, evaluating predisposition for future seizures, as well as differentiating epileptic from nonepileptic paroxysmal events.
“The capability of cEEG to detect these and many other abnormalities has a significant bearing on patient management and prognosis,” the article stated.
Yet, the article also noted underutilization of cEEG in pediatric medicine despite these “obvious” benefits, highlighting a substantial gap between clinical and utility use.
The case for impact on functional outcomes is strongest for cEEG in pediatric populations, with seizure burden being correlated with functional status at discharge.
The Expanding Case for cEEG
A 2013 study in the U.S. and Canada found relatively few institutions had clinical pathways to addressing cEEG use, with still fewer able to offer the service through certified technologists. The survey further revealed that many institutions limited cEEG to only critically sick patients. Moreover, they did not always provide true cEEG monitoring, instead continuously acquiring data and periodically interpreting results.
Given the growing body of clinical support for use in cEEG, as well as the reduced barriers to entry for cEEG monitoring, it seems evident that continuous EEG monitoring will play an increasingly important role in effective management of patients who can benefit from cEEG.