Richard P. Brenner

Computerized EEG spectral analysis in elderly normal, demented and depressed subjects

Computerized spectral analysis of the EEG was performed in 35 patients with Alzheimers disease and compared to patients with major depression (23) and healthy elderly controls (61). Compared to controls, demented patients had a significant increase in the theta and alpha 1 bandwidths as well as an increased theta-beta difference. The parasagittal mean frequency, beta 1 and beta 2 activity were significantly decreased. Depressed patients differed from demented patients, particularly at the lower end of the spectrum, having significantly less delta and theta activity. Like the demented group, depressed patients also had a decreased parasagittal mean frequency, beta 1 and beta 2 when compared to controls. In demented patients, there was a high correlation between several spectral parameters (parasagittal mean frequency, delta and theta activity, and the theta-beta difference) and the Folstein score, EEG measures used for discriminant analysis were more accurate in identifying demented patients who had lower Folstein scores.

Periodic Eeg Patterns: Classification, Clinical Correlation, and Pathophysiology

In this article, we review periodic EEG patterns, which have been classified into four different types based on their interval duration (short or long) and topographic distribution (lateralized, bilaterally independent, or diffuse and synchronous). The four patterns are: (1) periodic lateralized epileptiform discharges; (2) bilateral independent periodic lateralized epileptiform discharges; (3) periodic short-interval diffuse discharges; and (4) periodic long-interval diffuse discharges. We also discuss morphology, etiologies, and clinical correlates of each pattern and possible pathophysiological mechanisms of periodicity.

The ACNS subcommittee on research terminology for continuous EEG monitoring: proposed standardized terminology for rhythmic and periodic EEG patterns encountered in critically ill patients.

Continuous EEG monitoring is becoming a commonly usedtool in the assessment of brain function in critically illpatients. However, there is no uniformly accepted nomencla-ture for the EEG patterns frequently encountered in thesepatients, such as periodic discharges, fluctuating rhythmicpatterns, and combinations thereof. Similarly, there is noconsensus regarding which patterns are associated with on-going neuronal injury, which needs to be treated, or howaggressively to treat them. The first step in addressing theseissues is to standardize terminology to allow multicenterresearch projects and to facilitate communication. To thisend, we gathered a group of electroencephalographers withparticular expertise or interest in this area to develop stan-dardized terminology to be used primarily in the researchsetting. One of the main goals was to eliminate terms withclinical connotations, intended or not, such as “triphasicwaves,” a term that implies a metabolic encephalopathy withno relationship to seizures. We also decided to avoid the useof “ictal,” “interictal,” and “epileptiform” for the equivocalpatterns that are the primary focus of this report.A standardized method of quantifying interictal dis-charges is also included for the same reasons, with no attemptto alter the existing definition of epileptiform discharges(sharpwavesandspikes Noachtaretal.,1999 .Similarly,weare not necessarily suggesting abandonment of prior termssuch as periodic lateralized epileptiform discharges (PLEDs)and triphasic waves for clinical use.This is a proposal subject to future modifications basedon use and feedback from others.

Is It Status

Summary: Nonconvulsive status epilepticus (NCSE) is difficult to diagnose in the obtunded/comatose patient. Such patients often have other serious medical conditions, and the diagnosis is frequently delayed. We review criteria for diagnosis, treatment, and prognosis of NCSE in this setting. Terms that have been used to describe SE in obtunded/comatose patients without tonic–clonic convulsions include subtle generalized SE, electrographic SE, SE in comatose patients, generalized electrographic SE, non–tonic–clonic SE, subclinical SE, and NCSE. Sometimes the same term has been used when describing different disorders, and different terms are often applied for the same entity. The incidence of NCSE in obtunded/comatose patients is uncertain. Clinically they may display subtle, intermittent focal or multifocal rhythmic movements suggestive of seizures; there may not be movements. NCSE can occur in a variety of disorders, including hypoxia, metabolic disturbances, and after convulsive seizures. A number of EEG patterns have been described in NCSE, and many of these are controversial, particularly as to whether they are ictal. These include periodic lateralized epileptiform discharges (PLEDS), bilateral independent PLEDS (BIPLEDS), periodic epileptiform discharges (PEDS), which can be either focal or generalized, and generalized triphasic waves (TWs). The diagnostic criteria for NCSE also are controversial, and there are no agreed‐on criteria to diagnose NCSE in obtunded/comatose patients, nor is there consensus on how it should it be treated. Furthermore, outcome is poor, and several studies suggest that treatment may not be helpful.

Diagnostic efficacy of computerized spectral versus visual EEG analysis in elderly normal, demented and depressed subjects.

Computerized spectral and visual EEG analyses were performed in 35 patients with Alzheimers disease (AD) and compared to 23 patients with major depression and to 61 healthy elderly controls. In particular, we were interested in the diagnostic efficacy of these two techniques in the identification of cases of AD with only mild cognitive impairment (as measured by the Folstein Mini-Mental State score). For the computer analyzed data, in differentiating AD patients from controls, the spectral pooled parasagittal mean frequency was used. In comparing AD patients to depressed subjects, a combined parasagittal delta and theta spectral score was employed. Visual analysis criteria were based on the severity of generalized EEG abnormalities (with or without focal features). We found that spectral analysis afforded only modest advantages over visual EEG analysis in differentiating AD patients from elderly controls as well as from those with major depression. Since the degree of spectral and visual EEG abnormalities correlated with the severity of dementia, both tests more often correctly classified those AD patients with lower Folstein scores. Also, both tests identified primarily the same patients. We did not find the computer to be more sensitive than the eye in the identification of AD patients with mild impairment. However, computerized spectral data was derived from only 4 channels, while 16 channels and a longer recording time were used for visual analysis. In addition, some areas which have been reported to show EEG abnormalities in AD were not included in the computerized data.

A Psychiatric Study of 247 Liver Transplantation Candidates

This study prospectively evaluated 247 consecutive liver transplantation candidates for the presence of psychiatric disorders. While one-half did not meet DSM-III criteria for a psychiatric diagnosis, 18.6% had delirium, 19.8% had an adjustment disorder, 9% had alcohol abuse or dependence, 4.5% had major depression, and 2% had other drug abuse or dependence. Delirious subjects were significantly more likely to have a lower serum albumin, lower Mini-Mental State exam scores, higher Trailmaking Test scores (both A and B), and more dysrhythmia on electroencephalogram (EEG). In addition, while both delirious and nondelirious subjects were judged to have high levels of overall stress, those with delirium had significantly poorer adaptive functioning and lower occupational, family, and social scale ratings. Thus, while all liver transplant candidates are under substantial psychosocial stress and require psychosocial support, those identified as being delirious require particular attention because of their numerous cognitive, medical, and psychosocial problems.

Electroencephalography of the elderly.

This review of the electroencephalography (EEG) of the elderly is concerned with definitions of terms; normal EEG variability during wakefulness, drowsiness, and sleep; paroxysmal activity; and EEG (including results of computerized spectral analysis) in selected disorders commonly affecting the elderly.

Electroencephalography in syncope.

Electroencephalographic (EEG) findings in syncope are reviewed. There are four major categories of syncope: neurally mediated (neurocardiogenic), neurologic, decreased cardiac output, and orthostatic hypotension. However, regardless of cause, whether the syncope is due to a vasovagal effect, a cardiac arrhythmia, an epileptic seizure, or hypotension, EEG findings are similar and reflect cerebral hypoperfusion. Initially there may be a slowing of background rhythms. This is followed by high amplitude delta activity, maximal anteriorly. If the hypoperfusion persists there is subsequent flattening of the EEG. The EEG returns to normal in the reverse sequence. In cases with severe and prolonged ischemia, convulsive syncope may occur at the time of the EEG flattening. Although not an epileptic phenomena, clinically this is often mistaken for epilepsy. Conversely, epileptic disorders, such as the ictal bradycardia syndrome, may occasionally mimic syncope. Therefore, in patients in whom EEGs are performed for the evaluation of an episode of loss of consciousness, simultaneous ECG should be used.

Planned ictal FDG PET imaging for localization of extratemporal epileptic foci

Summary: Purpose: This work demonstrates the feasibility of planned ictal positron emission tomography (PET) with [18F]fluoro‐2‐deoxy‐glucose (FDG) for localization of epileptic activity in patients with frequent partial seizures of extratem‐poral origin.

Utility of EEG in Delirium: Past Views and Current Practice

The EEG is a useful and, at times, an essential test in the evaluation of delirium. In most patients with delirium, the EEG will show diffuse slowing and thus is helpful in differentiating organic etiologies from functional, psychiatric disorders. The degree of the EEG changes correlates with the severity of the encephalopathy so that the EEG may be used to help monitor therapy. In some delirious patients, the EEG may indicate whether the patient is suffering from focal, rather than global, impairment. Furthermore, the EEG is the only test that can identify an ongoing epileptic state (e.g., nonconvulsive status epilepticus) as being responsible for the clinical picture of confusion. Other electrophysiological tests that may prove helpful in the evaluation of delirium, such as computerized EEG spectral analysis, topographic brain mapping, and sleep studies, are briefly reviewed.