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Classification of deviant average evoked responses
700
INTERNATIONAL FEDERATION - 7TH CONGRESS
than the most recent, but not by individual events earlier than the most recent.
128. Classification of deviant average evoked responses.-K. A. Kooi and A. G. Clague (Ann Arbor, Mich., U.S.A.). Experience with the localization of 36 supratentorial tumors through multiareal recording of average visually evoked responses has shown that the alterations of compound evoked potentials may be classified descriptively according to 1) segment of the response affected, 2) type of change, and 3) area of maximal deviation. The effects of discrete lesions are typically selective, involving only a portion of the response, and variously manifested by augmentation or diminution of voltage, advanced or delayed peak culmination, rounding, atypical distribution, spatial stereotypy, or fusion o f components. Anomolous waves, not corresponding to any known event, may be observed. Each of the 3 normally occurring surfacenegative waves (peak latencies of approximately 40, 90 and 150 msec respectively) may be differentially affected in respect to the others. Local augmentation of voltage is largely limited to the initial surface negativity (I) or subsequent positivity (II) or both. The second surface negativity (III) is rarely augmented but is commonly depressed, without constant relation to alterations of preceding waves. Of all components, the third surface negativity (V) is most likely to evidence depression, often in conjunction with the preceding positivity. Recognition of the presence of deviant activity generally requires the existence of a substantial asymmetry between responses recorded from homologous cerebral regions. Detection of the side and area of involvement rests upon the establishment of 1) lack of correspondence of the observed pattern with the expected normal pattern for the region in question and 2) lack of correspondence of the pattern with that evident in the remainder of the areal samples, both ipsi- and contralateral to the site under study. Satisfactory localization of most supratentorial tumors can be achieved on the basis of the foregoing considerations. Twenty-four-point spatiotemporal arrays of responses recorded from representative patients will be utilized to illustrate various aspects of the classification procedure. 129. EEG spectral analysis in coma.-F. Ferillo, C. Rivano, G. Rosadini, G. F. Rossi and C. Turella (Genova, Italy). A spectral analysis of the EEG activity of patients in comatose states of variable degree due to
organic brain lesions has been made. (1.) Oscillatory periodic potentials ( " r h y t h m i c " activity) are recorded in all degrees of coma except in the terminal stage of vegetative coma or coma "dbpassd". A certain organization of the cerebral electrical activity is therefore compatible with a severe disorganization of cerebral functioning. (2.) The dominant rhythmic activity belongs to the delta band. Theta as well as alpha rhythms can be recorded. No clear-cut relation between depth of coma and type of rhythmic activity is apparent.
130. On the diagnosis of cerebral death--a prospective study.-J. Korein and M. Maccario (New York, N.Y., U.S.A.). The initial criteria used for admission to the study included coma, fixed dilated unreactive pupils, absent corneal reflexes, absent deep tendon reflexes, and absent clinical response to any painful stimuli. Clinical data that were pertinent to the evaluation such as drug toxicity, hypothermia, metabolic disorders and encephalitis were carefully documented. Later some patients were also included in whom these criteria were not completely present, but in whom the progressive course suggested that they might soon be in the previously described state. The following provocative procedures were carried out during the EEG recording: delivery of painful stimuli, ice water caloric stimulation, photic stimulation, and Methylphenidate hydrochloride (Ritalin), 50-100 mgs i.v. The data were recorded using an 8-channel Grass EEG Model 6A, and a 4-channel magnetic tape recorder for subsequent analysis of evoked responses. No patient was pronounced dead by the use of these criteria during the course of the study, and full supportive therapy was continued to the time of final cardiovascular collapse. Serial EEGs from 4 to 48 h apart were taken in patients who survived for that period of time. Thus far, a total of 28 patients were studied with 58 EEGs. Of the 28 studied, 25 had isoelectric EEGs prior to their death. Six of these isoelectric records had some muscle artifact in the EEG tracing indicating that peripheral activity was still present. All patients in this study died. Caloric stimulation, photic stimulation, and Methylphenidate hydrochloride injection occasionally produced phenomena such as shivering, decerebrate movements and muscle artifacts which will be described. In four patients, a phase of the EEG prior to death was observed which was characterized by a sequence of cyclic activity of sharp spikes, slowing, triphasic waves and suppression bursts, with a periodicity ranging from 30 sec to 3 min.
INTERNATIONAL FEDERATION - 7TH CONGRESS
than the most recent, but not by individual events earlier than the most recent.
128. Classification of deviant average evoked responses.-K. A. Kooi and A. G. Clague (Ann Arbor, Mich., U.S.A.). Experience with the localization of 36 supratentorial tumors through multiareal recording of average visually evoked responses has shown that the alterations of compound evoked potentials may be classified descriptively according to 1) segment of the response affected, 2) type of change, and 3) area of maximal deviation. The effects of discrete lesions are typically selective, involving only a portion of the response, and variously manifested by augmentation or diminution of voltage, advanced or delayed peak culmination, rounding, atypical distribution, spatial stereotypy, or fusion o f components. Anomolous waves, not corresponding to any known event, may be observed. Each of the 3 normally occurring surfacenegative waves (peak latencies of approximately 40, 90 and 150 msec respectively) may be differentially affected in respect to the others. Local augmentation of voltage is largely limited to the initial surface negativity (I) or subsequent positivity (II) or both. The second surface negativity (III) is rarely augmented but is commonly depressed, without constant relation to alterations of preceding waves. Of all components, the third surface negativity (V) is most likely to evidence depression, often in conjunction with the preceding positivity. Recognition of the presence of deviant activity generally requires the existence of a substantial asymmetry between responses recorded from homologous cerebral regions. Detection of the side and area of involvement rests upon the establishment of 1) lack of correspondence of the observed pattern with the expected normal pattern for the region in question and 2) lack of correspondence of the pattern with that evident in the remainder of the areal samples, both ipsi- and contralateral to the site under study. Satisfactory localization of most supratentorial tumors can be achieved on the basis of the foregoing considerations. Twenty-four-point spatiotemporal arrays of responses recorded from representative patients will be utilized to illustrate various aspects of the classification procedure. 129. EEG spectral analysis in coma.-F. Ferillo, C. Rivano, G. Rosadini, G. F. Rossi and C. Turella (Genova, Italy). A spectral analysis of the EEG activity of patients in comatose states of variable degree due to
organic brain lesions has been made. (1.) Oscillatory periodic potentials ( " r h y t h m i c " activity) are recorded in all degrees of coma except in the terminal stage of vegetative coma or coma "dbpassd". A certain organization of the cerebral electrical activity is therefore compatible with a severe disorganization of cerebral functioning. (2.) The dominant rhythmic activity belongs to the delta band. Theta as well as alpha rhythms can be recorded. No clear-cut relation between depth of coma and type of rhythmic activity is apparent.
130. On the diagnosis of cerebral death--a prospective study.-J. Korein and M. Maccario (New York, N.Y., U.S.A.). The initial criteria used for admission to the study included coma, fixed dilated unreactive pupils, absent corneal reflexes, absent deep tendon reflexes, and absent clinical response to any painful stimuli. Clinical data that were pertinent to the evaluation such as drug toxicity, hypothermia, metabolic disorders and encephalitis were carefully documented. Later some patients were also included in whom these criteria were not completely present, but in whom the progressive course suggested that they might soon be in the previously described state. The following provocative procedures were carried out during the EEG recording: delivery of painful stimuli, ice water caloric stimulation, photic stimulation, and Methylphenidate hydrochloride (Ritalin), 50-100 mgs i.v. The data were recorded using an 8-channel Grass EEG Model 6A, and a 4-channel magnetic tape recorder for subsequent analysis of evoked responses. No patient was pronounced dead by the use of these criteria during the course of the study, and full supportive therapy was continued to the time of final cardiovascular collapse. Serial EEGs from 4 to 48 h apart were taken in patients who survived for that period of time. Thus far, a total of 28 patients were studied with 58 EEGs. Of the 28 studied, 25 had isoelectric EEGs prior to their death. Six of these isoelectric records had some muscle artifact in the EEG tracing indicating that peripheral activity was still present. All patients in this study died. Caloric stimulation, photic stimulation, and Methylphenidate hydrochloride injection occasionally produced phenomena such as shivering, decerebrate movements and muscle artifacts which will be described. In four patients, a phase of the EEG prior to death was observed which was characterized by a sequence of cyclic activity of sharp spikes, slowing, triphasic waves and suppression bursts, with a periodicity ranging from 30 sec to 3 min.