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Continuous EEG (cEEG)

Overview of Continuous EEG for Patients

Continuous electroencephalography (cEEG) monitoring in the Intensive Care Unit (ICU) is a specialized medical procedure to monitor brain activity in people who are critically ill. An electroencephalogram (EEG) is a test that records brain waves, or the brain’s electrical activity, as you think, experience emotions, or perform tasks. EEG helps doctors see how your brain works or, when injured, how it works incorrectly. EEGs are usually recorded for short periods, such as one to two hours, and can help detect a wide variety of problems with the brain.

cEEG uses the same equipment and technology as EEG: Approximately 30 electrodes (small metal or plastic discs) are attached painlessly to the scalp with a special glue. The electrodes are connected to an EEG machine, which records and displays the brain’s electrical activity on a computer monitor. An EEG can detect abnormal signals, such as spikes or sharp waves seen in patients with seizures or slowing brain waves, indicating that part of the brain is not working normally.

cEEG records brain activity for days to weeks in people in the ICU. These patients have either had a brain injury such as stroke, traumatic brain injury, or brain infection or are at high risk for brain injury. By recording continuously at the bedside, doctors can see if and when brain function worsens and begin treatment designed to prevent further injury. Your care team can also use cEEG to determine if the treatment works.

You or your loved one may undergo cEEG while you are in the ICU if your clinical team determines that it can help. cEEG is commonly used in the following conditions or situations:

  • Seizures, epilepsy, and status epilepticus (prolonged seizures that do not stop on their own)
  • Ischemia, or lack of blood flow to the brain
  • Traumatic brain injury, or injury caused by being hit in the head or the head striking another object
  • Brain infections such as meningitis or encephalitis
  • Cardiac arrest, or condition when the heart stops beating, resulting in lack of blood flow to the brain)
  • Metabolic encephalopathy (confusion or coma because of abnormalities in blood chemistries or infection)
  • After procedures such as neurosurgery or angiograms
  • Coma (a state of unresponsiveness) without a clear cause
  • Assessing brain function in patients on high-dose sedating or paralyzing medications
medical team analyzing results on a laptop

The results of cEEG are available at the bedside, allowing neurocritical care clinicians to view changes in brain activity. Information from each cEEG machine is also transmitted to a central station, where an EEG technologist monitors the cEEG continuously and alerts a doctor if there are any abnormal changes in brain function. Specialized doctors (epileptologists or neurologists) interpret the cEEGs and discuss the results as soon as possible with neurocritical care specialists, who can begin or change treatment promptly based on the EEG results. 

Quantitative EEG analysis (qEEG), sometimes called trends, is a method to continuously monitor and analyze the activity of cEEG. This technique turns the cEEG into a simplified picture of brainwave activity and displays the results of this analysis over time. It allows caregivers at the bedside to recognize changes in brain function quickly, helps technologists and doctors monitor multiple patients simultaneously, highlights subtle brain activity changes, and displays brain function over extended periods, such as one to two hours. Sometimes, qEEG can generate alerts or notifications when an abnormal EEG pattern occurs. qEEG is often combined with the results of other brain monitors to get more information about overall brain health.

cEEG in the ICU is crucial for assessing and managing brain-related problems. It provides valuable information about brain function over time and can help predict, detect, and monitor the effects of treatment for a variety of brain injuries that occur in critically ill patients. Ultimately, cEEG empowers doctors to make more informed decisions about a patient’s care and may help improve neurological outcome or recovery.

nurse holding senior patient's hand

Information for Physicians and Other Healthcare Providers

Continuous electroencephalography (cEEG) monitoring in the Intensive Care Unit (ICU) is a specialized medical procedure that tracks brain activity in critically ill patients. Routine electroencephalogram (EEG) testing records the brain’s electrical activity, offering insights into its normal or impaired functioning. Traditionally, EEGs are brief, lasting around one to two hours, and help detect various brain abnormalities.

In cEEG, the same technology is employed, but the monitoring is prolonged, spanning days to weeks. cEEG is optimized for patients in the ICU who have experienced or are at risk of brain injury due to a variety of neurological diseases. These abnormalities can be complicated to detect in patients with abnormal physical and neurological exams. cEEG is very sensitive to changes in brain function in real-time but nonspecific as to the cause of brain dysfunction, so other tests are often needed to pinpoint the etiology. Continuous monitoring enables prompt identification of deteriorating brain function, guiding timely intervention to mitigate further damage. In some cases, cEEG can help gauge the effectiveness of any treatments initiated.

Common indications for cEEG include:

  • Seizures, epilepsy, and status epilepticus (8-37% of ICU patients, often subclinical)
  • Suspected nonconvulsive status epilepticus (in patients with altered mental status)
  • Unusual “spells” in the ICU
  • Ischemic and hemorrhagic stroke
  • Aneurysmal subarachnoid hemorrhage
  • Traumatic brain injury
  • Infections of the central nervous system
  • Cardiac arrest for other hypoxic ischemic encephalopathy
  • Metabolic encephalopathy
  • Post procedures such as neurosurgery or angiograms
  • Coma of unknown etiology
  • Assessing the effects of sedating or paralyzing medications

Results from cEEG are available at the bedside, allowing immediate assessment by neurocritical care staff. Data are also transmitted to a central station for continuous monitoring by EEG technologists, who alert physicians to any abnormal changes. Specialized neurophysiologists interpret cEEG findings promptly, collaborating with Neurocritical Care specialists to adjust treatment strategies as necessary.

Quantitative EEG analysis (qEEG) supplements cEEG by simplifying brainwave patterns and displaying activity trends over time. This facilitates swift recognition of brain function changes, efficient monitoring of multiple patients, and identification of subtle abnormalities. qEEG may generate alerts for abnormal EEG patterns and is often integrated with other brain monitoring techniques for comprehensive assessment.

Our cEEG program is continuously staffed by in-house EEG technologists who can initiate cEEG recording and monitor brain activity. Expert neurophysiologists are always on call and communicate rapidly to the neurocritical care team. We are part of the Critical Care EEG Monitoring Research Consortium and are dedicated to continuously optimizing cEEG.

cEEG in the ICU is invaluable for evaluating and managing various brain-related issues in critically ill patients. It provides continuous insights into brain function, aiding in predicting, detecting, and monitoring treatment effects on brain injuries. Ultimately, cEEG enhances decision-making and may contribute to better neurological outcomes.

Medically Reviewed by Vladimir Shvarts, MD, FACNS on June 21, 2024