James T. Kelley

Reliability of rapid clinical staging of all night sleep EEG.

The recording of all night sleep EEGs on a portable cassette recorder, and the rapid visual staging of the sleep records at 20 times real time, represent innovations in sleep research methodology. The reliability of sleep stager percentages obtained in this way is examined in this article. In the first of two studies, all night sleep records for six individuals were each staged twice by each of two qualified electroencephalographers. Inter-rater and intra-rater reliability assessed by intraclass correlation methods was modest, requiring the averaging of results from two judges to reach acceptable levels. Following consistency training, the two electroencephalographers staged all night sleep records for six additional subjects. Acceptable reliability was achieved in measurement of stages 2, 3, 4 and REM, although difficulty in reliably distinguishing stage 1 from the awake stage persisted. On the basis of these results, rapidly paced visual interpretation of sleep records at 20 times real time is recommended as a feasible way of meeting demands imposed by innovations in the technology of recording sleep EEGs.

Photic driving and psychogeriatric diagnosis.

The electroencephalogram is a widely used instrument in distinguishing between dementia and functional disturbance in the elderly. The EEG changes that accompany pathological senility are the slowing of the dominant posterior rhythms, and increases in theta and delta range activity. 1,2 Early in the clinical course of presenile or senile dementia, however, the EEG may be entirely normal. This is possibly due to a lag of the electroencephalographic findings in relation to the clinical signs and symptoms of the diseases. Alternatively, this could be secondary to undetected slowing in the EEG that does not go below accepted alpha range limits. There is also good evidence that some neuropathological subtypes of dementia (Picks Disease) have little effect upon the EEG. These difficulties in early EEG diagnosis of dementia parallel the difficulties of the clinician. For it is early in the clinical presentation of an organic brain syndrome, that the problem of a pseudodementia or a functional disturbance, presenting with the cognitive and emotional symptomatology more typical of a dementing process, so frequently occurs. Likewise, the earliest presentation of dementia proper can be depression or other more typical functional signs and symptoms. 3,4 An electrographic parameter that may be more sensitive in discriminating functional from organic disorders is the non-convulsive cerebral response to intermittent photic stimulation (photic driving). Kooi 5 showed that in general the photic driving response was reduced in all types of neurological pathology, including diffuse cerebral disease associated with dementia. Coull and Pedley 6 recently reported that it was the development of the photic response in terms of frequency, that best correlates with lateralized cerebral pathology. Hamel et at.,? using the compressed spectral array, showed that the quantified photic driving response in both its fundamental and harmonic components was directly related to the degree of encephalopathy produced by renal failure, and highly correlated with slowing in the same patients. In functional conditions, Ulett et al.8 reported that the amount of driving, especially at higher flash frequencies or at higher harmonics, was correlated with anxiety and susceptibility to stress. Klaiber et al.9 reported that depressed women had significantly increased amounts of driving to photic stimulation than age matched non-depressed women. The subject of this study is to see if this reported divergence in photic driving between functional and organic disorders could be used to better discriminate between functional and organic psychiatric conditions in the elderly.

Failure of Pavulon to Consistently Provide Adequate EMG Attenuation for Recording Electrocerebral Inactivity

It is important for the electroencephalographer to consult regularly and closely with the clinician ordering EEGs. This is particularly true in the relatively specialized area of recording for confirmation or support of the clinical impression of brain death. In the instances when a record is being run primarily to confirm the absence of electrocortical activity, it is clearly possible that artifact may be so high in the recording that such a determination is difficult or impossible. A particular artifact of concern is that of persisting muscle potential. As demonstrated in the cases above, this can be promptly eliminated with the use of the muscle relaxant succinylcholine chloride (Anectine). Often the use of pancuronium bromide (Pavulon) at a level that causes an equal clinical relaxation, leaves residual electrical muscle potentials that continue to make interpretation of the EEG difficult, if not actually impossible with any degree of certainty.

EEG, ALCOHOL, AND ALCOHOLISM

Publisher Summary Electrophysiological sleep studies may provide clinically useful information for separating primary depressive illness from alcoholism. Separation of primary depression from alcohol abuse or dependence from primary alcoholism with depression is a formidable task. The presenting alcoholic almost invariably has a sleep disturbance, appetite disturbance, dysphoric mood, loss of interest in sex, and often has suicidal ideation. Available electrophysiological tests include electroencephalogram (EEG), the pattern-reversal visual evoked potential, the short-latency auditory brainstem evoked potential, and long- and short-latency somatosensory evoked potentials. Clinically significant abnormalities in these tests should be considered evidence of neurological dysfunction secondary to the neurological complications associated with alcoholism or another neuropathological process. Sleep studies, long-latency evoked potentials, and digital-frequency EEG analysis all show protracted significant changes in the recovering alcoholic. A knowledge of the specific types of EEG changes seen in withdrawal, alcohol withdrawal delirium, and other syndromes associated with alcoholism, when integrated with other clinical data, makes routine EEG valuable to the clinician in specific cases.

EEG AND PSYCHOTROPIC DRUGS

Publisher Summary This chapter focuses on electroencephalogram (EEG) findings to illustrate changes in the central nervous system (CNS) function produced by psychotropic medications. The EEG is used in two quite distinct ways in the study of medication effects. The computer analysis of the EEG activity demonstrates combinations of changes in the different frequency bands, which has proved useful in comparison of different compounds and subsequent identification of new compounds of potential clinical value. The computer analysis of acute drug effects should be recognized as quite different from the EEG changes expected in a patient routinely taking these medicines and the changes seen in visually interpreted EEG, read by clinical standards without serial record comparisons. In visually interpreted EEGs, chronic use of neuroleptic and antidepressant drugs has relatively little effect on the EEG, except when they have a hypnotic effect, which changes the level of consciousness or when they have a toxic effect producing the expected changes of toxicity.

Effects of age and alcohol abuse on pattern reversal visual evoked potentials.

The Pattern Reversal Visual Evoked Potential (PRVEP) was recorded in normal subjects and alcoholics. The recordings were made from the patients during withdrawal and repeated after three weeks of detoxification. It was found that the N76 latency was longer in the alcoholic patient in the withdrawal phase than in the normal subjects. The latency returned to normal range after detoxification in younger alcoholic patients but did not in the older alcoholics. The age-related increase in the N76 latency in the alcoholic patients was similar to that in normal subjects but more exaggerated. For alcoholics, the age-related change in the N76 latency reached significance, but was only a trend in normal subjects. The P100 latency demonstrated significant age-related change, but far less modification related to the alcoholism than the N76 latency. It is unclear at present whether the failure of the latency to return to normal in older patients after detoxification is related to longer periods of excessive drinking, or to a particular vulnerability of the older patients to continued use of alcohol.