EEG Could be More Widely Used to Identify Treatable Causes of Common Disorders in Hospital Patients, Say Researchers in Mayo Clinic Proceedings.
A retrospective study of patients who had in-hospital
electroencephalography (EEG) has established that EEG is a valuable tool
that could be deployed more widely to identify treatable causes of
impaired consciousness in the hospital setting. The study is published
in the April issue of the Mayo Clinic Proceedings.
Altered mental status (AMS) and paroxysmal spells of uncertain origin
are common among hospitalized patients. Impaired consciousness can
sometimes be linked to metabolic or cardiac causes, but some of these
spells may represent seizures or non-convulsive epilepsy, which can be
detected only by electroencephalography (EEG). Although EEG is the key
test in making these diagnoses, it is relatively underused in the
inpatient setting owing to lack of availability and neurologic
consultation at many hospitals in the United States.
In a unique analysis of non-intubated patients in a general hospital
setting investigators from the Department of Neurology, University of
California at San Francisco, studied hospital patients 18 years and
older who had inpatient EEG for an indication of spells or altered
mental status during a six-year period from January 2005. Their aim was
to determine the frequency of seizures and markers of epilepsy-like
activity detected by EEG.
The EEGs and reports were reviewed for ictal activity (electrographic
seizures), interictal epileptiform abnormalities (abnormal EEG activity
not associated with a clinical seizure), and nonepileptiform
abnormalities (not specific to a particular cause).
Demographic and clinical data were gathered from electronic medical
records to determine seizure predictors. Of the 1048 patients reviewed,
nearly 80% had an abnormal EEG finding, with the most common abnormality
being diffuse slowing, seen in 706 patients (67.4%). Seizures (ranging
from a single seizure to status epilepticus) were noted in 78 patients
(7.4%). Markers of seizure potential were found in 194 patients (18.5%).
Epileptiform discharges were found in 130 of the 970 patients (13.4%)
in whom no electrographic seizures were recorded, a finding that
indicates that these patients are at increased risk for seizures.
“The present findings underscore the relatively high frequency of seizures in non-critical hospitalized patients with spells or AMS, a finding that has seemingly been underappreciated by neurologists and non-neurologists alike,” observed lead investigator John P. Betjemann, MD, Assistant Clinical Professor, UCSF School of Medicine. “Because ictal disorders are treatable, having a relatively low threshold to obtain an EEG may be critical,” he said.
EEG is a resource-intensive test so investigators also sought to
identify clinical variables that are associated with positive EEG
findings to help physicians determine when this test should be ordered
and to guide health care systems regarding the need for EEG
However many hospitals do not have access to EEG technology. “One
major barrier involves a lack of trained technologists and
epileptologists to perform and interpret extended (24-hour) EEG
studies.…This study demonstrates that hospitals with limited resources
can perform relatively brief EEGs (1-6 hours) and still identify most
seizures in these non-critically ill patients,” Betjemann concluded.
In an accompanying editorial William O. Tatum, DO, Mayo Clinic,
Jacksonville, FL, and Joseph I. Sirven, MD, Mayo Clinic, Scottsdale, AZ,
comment, “…the importance of the article by Betjemann et al lies in
offering outcome measures using EEG in the general hospital setting.
This type of information will affect care from neurologists and
neurohospitalists by helping them design evidence-based monitoring and
treatment protocols….The precise value of continuous EEG-facilitated
diagnosis (eg, seizure detection coupled with treatment), and the
resulting improvements in patient outcomes, indeed suggests that cEEG
can provide a valuable ‘window to the brain’ for neurologically ill
Full bibliographic information
- “Diagnostic Yield of Electroencephalography in a General Inpatient Population,” by John P. Betjemann, MD; Ivy Nguyen, BS; Carlos Santos-Sanchez, MD; Vanja C. Douglas, MD; and S. Andrew Josephson, MD. DOI: http://dx.doi.org/10.1016/j.mayocp.2012.12.013
- “Does Electroencephalography Provide a ‘Window to the Brain’ for the Neurologically Ill?” by William O. Tatum, DO, and Joseph I. Sirven, MD. DOI: http://dx.doi.org/10.1016/j.mayocp.2013.02.002
Both appear in Mayo Clinic Proceedings, Volume 88, Issue 4 (April 2013), published by Elsevier.