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Biomedical subjects

J Gotman

Publications and source records attributed to J Gotman.

At least 109 records · Page 6Linked to original sources
PubMed1982

Correlations between EEG changes induced by diazepam and the localization of epileptic spikes and seizures.

We evaluated the EEG reaction to an intravenous injection of diazepam as an additional tool in difficult localization problems in epilepsy. The normal reaction to diazepam being an increase in beta activity, it was assumed that a poor increase indicated an abnormal region. This method was tested in 21 epileptic patients having chronically implanted intracerebral electrodes. Beta activity before and after injection was quantified by spectral analysis; increases were compared in homologous contralateral channels. In 12 of the 21 cases the area of poorest response to diazepam was identical to that of seizure onset. In 7 cases, there was some overlap between the area of poorest diazepam response and that of seizure onset, but they did not exactly coincide. In two cases there was no overlap between the two areas. Agreement was slightly higher when comparing diazepam response and area of highest interictal spike activity. This procedure is simple and without risk, particularly compared to the thiopental injection which is used for the same purpose. It is helpful in determining abnormal areas when localization information from various diagnostic sources are conflicting. Even when the epileptic focus is well defined, it can point to other poorly functioning areas.

Adult↗
PubMed1981

Frequency content of EEG and EMG at seizure onset: possibility of removal of EMG artefact by digital filtering.

EEG recordings of epileptic seizures from scalp and sphenoidal electrodes are frequently obscured by EMG activity from contracting scalp muscles. We have examined the possibility of selectively filtering the EMG artefact in order to make apparent the activity of cerebral origin. It has been shown that, during voluntary contractions of scalp muscles, most of the energy of EMG activity is above 15-20 Hz. We have shown, in recordings from 50 patients, that rhythmic activity at the onset of seizures uncontaminated by artefact had almost always a fundamental frequency lower than 25 Hz. From these two observations, we concluded that total elimination of activity above 25 Hz would eliminate most of the EMG activity, with a minimal risk of eliminating rhythmic cerebral activity. Thirty-one seizure contaminated by EMG activity were analyzed. Spectral analysis was used to assess the presence or absence of rhythmic activity at seizure onset, in the presence of obscuring EMG artefact. The spatial and temporal distribution of such a rhythmic activity was then revealed by a sharp digital filter which did not introduce phase distortions. Seizures recorded on computer tape were played back on paper following filtering. In 16 of the 31 cases it was possible to clarify the originally obscured recordings. In 7 cases, it was found that no rhythmic cerebral activity was hidden by the EMG, a finding which was also important. In the last 8 cases, it was not possible to determine with certainty the origin, cerebral or muscular, of fast rhythmic activity present at seizure onset.

Cerebral Cortex↗
PubMed1981

Interhemispheric relations during bilateral spike-and-wave activity.

Temporal relationships between homologous EEG channels of the two hemispheres were studied in patients whose EEGs showed bilateral synchronous spike-and-wave activity. Group A (seven patients) had generalized corticoreticular epilepsy and no sign of a localized predominant epileptogenic area. In group B (12 patients), the bilateral spike-and-wave activity was present in conjunction with a localized area of predominant epileptogenicity demonstrated by EEG, radiological, or clinical examinations. The measurement of small time differences between two homologous channels was performed by transforming the slope of the phase characteristic of the cross-spectrum into time, when the interchannel coherence was sufficiently high. Although measurements were not possible in every case (because of a lack of coherence or nonlinearity of the phase), results clearly indicated that the spike-and-waves in group A did not present significant interhemispheric time differences, whereas those of group B frequently presented a lead time (average 15 msec) from the side with the localized epileptogenic area. The method can be clinically useful to differentiate primary from secondary bilateral synchrony. The concept of secondary bilateral synchrony and the possible pathophysiological mechanisms explaining the time differences are discussed.

Adolescent↗
PubMed1981

The EEG in deep midline lesions.

We studied the electroencephalograms (EEGs) of 154 patients with well-defined diencephalic, mesencephalic, or posterior fossa lesions. Electrographic and clinical parameters were statistically evaluated. The results indicated considerable overlap of EEG abnormalities from different subcortical sites. Focal or lateralized abnormalities were relatively specific, suggesting a diencephalic lesion, whereas bilateral paroxysmal slow-wave disturbances were unspecific and not of precise diagnostic significance. There was no specific feature in this series to clearly distinguish the EEG pattern in deep midline lesions from that seen with diffuse cortical and subcortical encephalopathies.

Adolescent↗
PubMed1979

Automatic recognition of inter-ictal epileptic activity in prolonged EEG recordings.

A method of automatic recognition and quantification of inter-ictal epileptic activity in the human EEG had previously been developed and tested using short recordings from awake subjects. This paper describes the adaptation of the method for use during overnight recordings in free-moving unattended patients, in combination with the already existing seizure monitoring system. EEG s were recorded from scalp and sphenoidal electrodes, using cable telemetry and a PDP-12 computer. The spike and sharp wave recognition method allowed the on-line analysis of 16 channels. A section of the 16-channel EEG including 1 sec before and 1 sec after each detected spike was saved on digital magnetic tape. Upon completion of the monitoring session, the tape was played back on the EEG machine, giving a discontinuous tracing of spike sections; this constituted a highly concentrated view of the inter-ictal epileptic activity, in traditional paper form. The spike sections were further analyzed by computer to determine and display on the computer terminal the spatial and temporal distributions of the epileptic activity, providing a complete synopsis of the recording. Several examples of the type of information available from this anslysis are discussed in detail. False detection rates are given for 34 six hour recordings, indicating a high vari ability in the performance, mainly because of artefacts. It is concluded that the final computer displays could only be trusted after visual inspection of the EEG sections provided on paper. The variety of morphologies of artefacts appeared to preclude a total automatic elimination.

Electroencephalography↗
PubMed1978

The electromicrophysiology of delta waves induced by systemic atropine.

Delta waves in the EEG can be induced by the intravenous administration of atropine. In cats we have investigated with several computer averaging programs the relationship of extracellular unit discharge to the EEG on the surface and within the cortex. We have also studied the laminar profiles and the vertical current density profiles of these slow waves. Our results indicate that surface-positive delta waves are related to events associated with excitation of cortical neurons, while surface-negative delta waves are related to a decreased probability of unit firing suggesting the possibility of inhibition. Laminar analysis of atropine-induced slow waves indicated that these were probably generated by pyramidal cells in a similar way to delta waves induced by brain lesions. These results suggest that a disturbance in cholinergic input to the cortex might be responsible for delta waves in the EEG.

Animals↗
PubMed1976

Automatic recognition and quantification of interictal epileptic activity in the human scalp EEG.

An attempt was made at using a small computer to recognize and quantify interictal epileptic activity (spikes and sharp waves) in the human scalp EEG. To perform the automatic recognition, the EEG of each channel is broken down into half-waves. A half-wave is characterized by its duration and its amplitude relative to the background activity. A wave is characterized by the durations and amplitudes of its two component half-waves, by the second derivative at its apex measured relative to the background activity, and by the duration and amplitude of the following half-wave. Particular combinations of these parameters were found to characterize spikes and sharp waves and are used for their recognition and quantification. Specific methods are used for the rejection of spike-like or sharp wave-like wave forms such as eye blinks, muscle potentials and sharp alpha activity and were found to perform with a high level of reliability. Interchannel relationships are thoroughly examined to determine areas of maximal epileptogenicity. Sixteen channels can be analyzed in real time. Results are presented in a simple picture containing localizing and quantitative information. Specific questions regarding the time relationships of spikes in different channels can be asked interactively by the user. The system is of potential use in clinical electroencephalography.

Alpha Rhythm↗
PubMed1975

A quantitative comparison of traditional reading of the EEG and interpretation of computer-extracted features in patients with supratentorial brain lesions.

The EEGs of adult patients with suspected supratentorial brain lesions were recorded on paper and on magnetic tape, using a small computer. The spectra of 16 channels were computed on a 40 sec sample. For each channel, a ratio of the type (delta + theta)/(alpha + beta) was computed and displayed on the computer terminal, a measure of the asymmetry in slow wave activity between homologous areas of the head was also displayed. This display is called a canonogram. It is believed to be a meaningful representation of the important characteristics of the EEG in the presence of supratentorial lesions. In order to assess the clinical value of the canonogram, the presumed localization of the lesion obtained from the interpretation of the traditional EEG and from that of the canonogram were compared to the known location of the lesion is a group of 87 subjects. The comparison was made quantitative by the use of a structured report encoding the traditional interpretation and that of the canonogram as well as the reference data (unequivocal surgical, radiological and clinical localizing evidence). The results varied among the anatomical regions: whereas in the frontal and occipital regions the EEG was slightly more accurate than the canonogram, both methods were similar in the temporal areas and the canonogram seemed more accurate in the centro-parietal regions. An attempt was made to interpret these differences. Furthermore, three readers read the cononograms and gave very consistent interpretations. These results show the reliability and value of this simple computer display for the particular type of EEG studied.

Adult↗
PubMedDate not supplied

Effects of drug withdrawal on location of seizure onset.

Fourteen patients with intractable epilepsy, candidates for surgical treatment, were investigated with intracerebral electrodes because of the presence of multifocal abnormalities in surface recordings. EEG and video monitoring was performed during a period of reduction and/or discontinuation of anticonvulsant medication performed to precipitate seizure occurrence. The clinical and electrical patterns of seizures recorded during the withdrawal of anticonvulsant drugs were compared to those of the patients' habitual seizures observed on full medication. For each patient, we determined a profile of the clinical and electrographic seizure activity observed before the withdrawal of medication or reported by the patient prior to hospitalization. Following the reduction or cessation of medication, an increase in partial seizure frequency was observed in all patients. All but one of these partial seizures had the same clinical pattern as the habitual attacks of the patients, and the EEG manifestations were compatible with the baseline data. Seven of the 14 patients had secondarily generalized seizures; for each patient, these seizures had the same clinical and electrographic onset as their partial seizures. Only one patient had a single partial seizure having an EEG onset different from the other seizures occurring around that time and having a clinical pattern never experienced before. In conclusion, the reduction of anticonvulsant medication extremely rarely causes the appearance of seizures having an electrical onset or a clinical pattern different from those observed on full medication.

Adolescent↗
PubMedDate not supplied

Timing of seizure recurrence in adult epileptic patients: a statistical analysis.

Seizure diaries were maintained prospectively in 24 epileptic patients (19 with partial complex, three with partial simple, and three with primary generalized seizures) who were selected consecutively, had stable seizure patterns, were reliable historians, and were known to be compliant with medications. Diaries were maintained for an average of 237 days (range, 61-365), and an average of 18 seizures were recorded per patient (range, 5-76). Seizure patterns were analyzed by using the methods appropriate for a time series of events (point process). Two patients had a decreasing trend in seizure frequency. For 12 patients, seizure occurrence was indistinguishable from that of a Poisson process. The remaining 10 patients had an exponential distribution of seizure intervals, but did not fit other criteria for a Poisson process; 3 of these showed evidence for seizure clustering; none showed evidence for a seizure cycle. It is concluded that the pattern of seizure occurrence in most epileptic people is random, but in approximately 50%, it is not occurring according to a Poisson process. These observations indicate that seizure cycling and/or clustering are not common in epileptic patients, but do not exclude the possibility that seizures have been precipitated by some randomly occurring event, such as sleep deprivation or increased stress.

Adolescent↗
PubMedDate not supplied

Sleep alterations after acute administration of carbamazepine in cats.

Little is known about the effects of carbamazepine (CBZ) on sleep despite the relationship between sleep and epilepsy and the common clinical use of CBZ. As part of a larger study on sleep and interictal activity in kindled cats, we performed sleep recordings in 11 normal cats before and after acute administration of CBZ. Epidural screws (frontooccipital) and depth electrodes (amygdala and hippocampus) were implanted bilaterally for EEG recording. Supraorbital screws and neck intramuscular electrodes were inserted for EOG and EMG. Ten days after electrode implantation, recordings were made of animals for 2 consecutive nights to assess baseline sleep patterns. Before the third night, cats received a single oral dose of 100 mg CBZ. After washout, a second similar drug administration was given before the fourth night. Recordings were scored for wakefulness, stage I and II of NREM sleep, REM sleep, number of stage shifts, awakenings, and REM onsets. The administration of CBZ produced a significant decrease in duration and percentage of REM sleep (p less than 0.001) and an increase in stage I NREM (p less than 0.05). Total sleep time was increased (p less than 0.05); awakenings were shorter (p less than 0.01), and stage I episodes were longer (p less than 0.01).

Animals↗
PubMedDate not supplied

Effects of seizures, kindling, and carbamazepine on sleep organization in cats.

We studied the relationships between epilepsy, sleep, and anticonvulsant drugs in kindled cats. No sleep alteration was present at midkindling. When the animals became fully kindled, a reduction in REM sleep percentage and the number of entries into REM sleep were observed compared to baseline. In addition, with further seizures, an increase in the percentage of wakefulness appeared, accompanied by a further reduction in the number of entries into REM sleep. It therefore seems that there is a progressive disruption of sleep, dependent on the increasing number of tonic-clonic generalized seizures. After a seizure-free interval, REM sleep and wakefulness returned to baseline values. A reduction in the percentage of stage II compared to baseline was found and remained as a long-term effect of the kindling process. Acute administration of carbamazepine (CBZ) reduced the REM sleep percentage. This effect, paralleled by a reduction in the number of entries into REM sleep, was evident both at baseline and when the animals were fully kindled. After a large number of seizures, however, CBZ administration did not cause a further reduction in the already low percentage of REM sleep. Results are discussed with reference to previous literature. We propose a hypothesis of competition between seizure and REM sleep in the elimination of epileptogenic and hypnogenic factors.

Animals↗