Peter Gloor

Anatomic basis of amygdaloid and hippocampal volume measurement by magnetic resonance imaging

Both the amygdala and the hippocampus are involved in the pathogenesis of a number of neurologic conditions, including temporal lobe epilepsy, postanoxic amnesia, and Alzheimers disease. To enhance the investigation and management of patients with these disorders, we developed a protocol to measure the volumes of the amygdala and as much of the hippocampus as possible (approximately 90 to 95%) using high-resolution MRI. We present the anatomic basis of these two protocols and our results in normal control subjects. These volumetric studies of the amygdala may clarify the role of this structure in the pathogenesis of temporal lobe epilepsy.

MRI volumetric measurement of amygdala and hippocampus in temporal lobe epilepsy

We performed MRI volumetric measurements of the amygdala (AM), the hippocampal formation (HF), and the anterior temporal lobe in a group of 30 patients with intractable temporal lobe epilepsy (TLE) and in seven patients with extratemporal lobe foci. Measurements were analyzed with a semiautomated software program and the results compared with those of normal controls and correlated with the findings of all other investigations. In particular, we compared the results with the lateralization of epileptic abnormalities in the EEG. Volumetric studies of AM and HF showed lateralization of measurable atrophy consistent with that derived from extracranial and intracranial EEG examinations. The HF volumes were more sensitive and provided a lateralization in 87%. Combined measurements of AM and HF showed lateralization in 93%, always congruent with the results of EEG lateralization. This slight but important additional improvement in discrimination justifies using AM measurements in MRI volumetric studies of mesial temporal structures. Volumetric studies combined with other currently employed noninvasive techniques may diminish the need for invasive methods of investigation in patients with TLE.

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.

An assessment of the value of sleep-electroencephalography for the diagnosis of temporal lobe epilepsy

Abstract 1. 1. The diagnostic importance of sleep electroencephalography for the EEG diagnosis of temporal lobe epilepsy was studied in two groups of patients. Group I consisted of 228 temporal lobe epileptics who underwent temporal lobectomy for their seizures. Group II represents a sample of 100 patients who gave a typical history of temporal lobe attacks, but were not subjected to surgical therapy. 2. 2. In group I the EEG diagnosis of temporal lobe epilepsy was made without sleep in 94.3 per cent of the cases. In group II the EEG diagnosis of temporal lobe epilepsy was make in 72 out of the total number of 100 patients. In group II sleep was only necessary for the diagnosis in 6.9 per cent of the 72 patients in whom a positive EEG diagnosis of temporal lobe epilepsy could be made. Out of 25 cases in whom no clear EEG diagnosis was made 10 had sleep records taken with negative results. 3. 3. Among the 77 patients of groups I and II in whom sleep records were obtained 44 showed more active epileptic discharge during sleep, whereas 23 showed no such activating effect or even some reduction of epilepti-form abnormality during sleep. 4. 4. Patients with a history of nocturnal attacks are more likely than others to require sleep activation to bring out the epileptiform abnormality, although even in this group the number of cases in which the diagnosis can be made from the waking record is still high. The higher incidence of cases in which sleep is necessary for the EEG-diagnosis among patients giving a history of nocturnal attacks is statistically significant. 5. 5. No statistically significant difference was found between natural and drug-induced sleep with regard to their propensity to activate temporal lobe abnormalities. 6. 6. It seems that electrocorticograms taken in temporal lobe epileptics during general anesthesia tend to show less clear diagnostic signs than those taken under local anesthesia. 7. 7. The pathological lesions found in patients whose temporal lobe EEG abnormalities were activated by sleep and those found in patients where no such activation occurred show the same relative incidence of atrophic versus space-occupying lesions. 8. 8. The main conclusion drawn from these findings is that although sleep tends to activate the temporal lobe epileptiform abnormality in a majority of cases, sleep electroencephalography in a majority of cases, sleep electroencephalography need not be carried out as a routine procedure in patients giving a history of temporal lobe seizures, since in more than 90 per cent of the cases in which a positive EEG diagnosis can be made this diagnosis can be established in the waking record.

Comparison of traditional reading of the EEG and automatic recognition of interictal epileptic activity.

Abstract This paper describes the evaluation of a method which has been developed for the automatic recognition and quantification of interictal epileptic activity in the human scalp EEG, using a small laboratory computer. Since it is very difficult to obtain non-EEG information clearly localizing an epileptic focus, the evaluation was performed by determining the unequivocal errors and by comparing in the interpretation of the computer display to the traditional interpretation of the paper record. Sections of 2 min of EEG which should not contain any epileptic activity (from 30 normal subjects and 30 non-epileptic patients) were analyzed, yielding the very low detection rate of 0.2 spikes or sharp waves/min/16 channels. A comparison was then performed, using data from 50 epileptic patients, between the tradiational interpretation and the interpretation of the computer display; the latter included the number of spikes and sharp waves found in every channel and the phase relationships between channels. Each of two EEGers interpreted independently the paper record and the computer display and encoded their findings regarding the localization of the focus and the extent of the abnormality in a structured report. A quantitative comparison of structured reports indicated correlation of 58% for EEGer A and 61% for EEGer B between paper record and computer display, 72% between EEGers A and B for the paper records and 84% between EEGers A and B for the computer displays. This shows that the automatic and traditional interpretations give comparable results but that the automatic method allows for more consistent interpretations between electroencephalographers.

Trichinosis encephalitis: a study of electroencephalographic and neuropsychiatric abnormalities.

ESTIMATES of the incidence of trichinosis at autopsy in the United States range from 16 to 18 per cent.lr2 Approximately 350,000 persons each year acquire a new infection, and, of these, 16,000 manifest clinically detectable symptoms, with an over-all mortality rate estimated at 5 to 6 per It is well documented in the literature that the central nervous system may be involved in trichinosis.’3.7 The incidence of this complication is variously reported as 10 to 17 per cent.*p3 The mortality in cases with neurologic involvement has been found to be as high as 35 per cent.gJ0 The importance of recognizing this clinical syndrome is obvious. With the advent in recent years of an effective, although nonspecific, treatment in the form of steroid hormones, one feels even more urgently the necessity of early diagnosis.