Pre-operative EEG evaluation in frontal lobe epilepsy.
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Adolescent↗
Biomedical subjects
L F Quesney
Publications and source records attributed to L F Quesney.
False lateralization by surface EEG of seizure onset in patients with temporal lobe epilepsy and gross focal cerebral lesions.
Medically intractable temporal lobe seizures developed in 3 patients with radiological and clinical evidence of a gross focal cerebral lesion acquired early in life. All had bilateral independent epileptogenic discharges from the lateral and inferomesial regions of both hemispheres. Scalp and sphenoidal electroencephalographic (EEG) recordings suggested that the seizures originated from the side contralateral to the known cerebral lesion. Because the lateralizing evidence presented by the ictal EEG conflicted with the clinical data, depth electrodes were implanted stereotaxically to determine the side of onset of the seizures. These studies showed that the seizures originated from the limbic structures of the damaged hemisphere in all 3 patients. At operation the mesial temporal lobe structures showed gliotic changes in all. The patients have remained seizure-free for 3 to 13 years postoperatively. These findings suggest that depth electrode recordings may be required to clarify the lateralization of seizure onset in such cases. Extracranial EEG findings must be interpreted with caution in epileptic patients who have gross focal lesions.
Adult↗
Dopamine in the visual cortex of the cat.
The endogenous content of noradrenaline (NA) and dopamine (DA) was determined by radioenzymatic assays in three different areas of the occipital (visual) cortex, in normal cats as well as in DA-deafferented animals. The use of HPLC methodology enabled us to detect and measure in addition two metabolites of DA: 3, 4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA), thus confirming the existence of a DA innervation in this cortical region.
Animals↗
Alpha-1 adrenoceptors are decreased in human epileptic foci.
Cortical alpha-1 adrenoceptors were measured in tissues obtained from 10 patients immediately following temporal lobectomy for intractable partial epilepsy. At operation each patient exhibited spontaneous spiking restricted to either the anterior (n = 5) or posterior (n = 5) portion of the first two temporal gyri. Control samples were obtained from the nonspiking half of the same gyrus. Receptor-binding assays were performed on isolated cortical membranes using [3H]prazosin. There was a reduction (p less than 0.01) in the receptor density (beta max) of the sites in the epileptic foci without any change in affinity (mean +/- SEM): spiking--beta max, 160.5 +/- 11.3 fmol/mg protein; affinity, 0.17 +/- 0.04 nM; nonspiking--beta max, 218.8 +/- 15.6 fmol/mg protein; affinity 0.17 +/- 0.04 nM. This relative decrease in alpha-1 adrenoceptor density may be the substratum of a noradrenergic hyposensitivity that could contribute to a localized diminution in inhibitory mechanisms in epileptic foci.
Adult↗
Clinical and EEG features of complex partial seizures of temporal lobe origin.
The electrographic and clinical behavioural manifestations of 96 temporal lobe seizures are reviewed from recordings in 19 patients who were submitted to stereotaxic depth electrode implantation in temporal and frontal lobes. Focal onset in hippocampus was recorded in 40% of the seizures. Sixty percent of temporal lobe seizures exhibited a regional seizure onset but in two-thirds of these ictal changes were restricted to amygdaloid and hippocampal structures. Thus, in approximately 80% of seizures, the onset of ictal EEG changes resided in the mesial temporal structures. The main behavioral manifestations observed during seizure discharge restricted to one temporal lobe included warning (67%), motionless stare (24%), automatism (22%), and head-body turning (24%). The predominant ictal behavioural manifestations observed during seizure spread to contralateral temporal and extratemporal structures included warning (3%), motionless stare (36%), automatism (77%), and head-body turning (81%). The direction of head turning did not provide reliable lateralization as to the side of seizure onset.
Adult↗
Differential aspects of sleep epilepsy.
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Epilepsy↗
The place of stereotactic depth electrode recording in epilepsy.
A series of 70 patients studied with stereotactically implanted depth electrodes is analyzed. Indications and grouping fall into three main categories: the bitemporal series (52 patients), where there is ambiguity as to the lateralization of the focus; the unilateral series (6 patients), where the main problem is one of localization within one hemisphere, and the generalized and/or multifocal series (12 patients), where a primary focus is suspected. The best indication is represented by the group of 'bitemporal cases' which turned out to have a well-lateralized onset with intracerebral recording.
Electrodes, Implanted↗
Localization of epileptic foci.
This chapter is devoted to the contribution of long-term EEG and behavioral monitoring to the localization of epileptic foci. Combined EEG and video monitoring may clarify the clinical seizure pattern reported by history; it may confirm or invalidate its localizing significance. It may also reveal unsuspected multiple clinical seizure patterns which may or may not correspond to multiple areas of seizure onset. The localizing evidence derived from interictal EEG abnormality provides valuable additional diagnostic information, identifying a likely area of seizure onset. Automatic spike recognition may improve the quality of the information provided by interictal activity by providing otherwise unavailable quantitative information. The main application of EEG monitoring is for detecting the region of seizure onset. This is important for the identification of seizure type, the differentiation between epileptic and non-epileptic seizures and the preoperative localization of seizure onset. Reliable localization in patients with partial seizures depends upon demonstration of a precise focal or regional onset of the ictal EEG changes occurring prior to or simultaneously with clinical seizure manifestations. Use of intracranial electrodes is indicated when monitoring with extracranial electrodes has not provided unequivocal localization of seizure onset. Automatic seizure recognition and phase analysis may again increase the yield of monitoring in localizing epileptogenic foci.
Automation↗
Monitoring at the Montreal Neurological Institute.
Long-term monitoring of epileptic patients who are candidates for surgical therapy has developed at the Montreal Neurological Institute and Hospital over the last 15 years. Given the large number of patients being investigated, we had to develop procedures which were not labor-intensive. Our monitoring sessions require only the regular supervision of nursing staff. This allows monitoring to take place 7 days a week and 24 h a day on 2 or 3 patients, with minimal personnel requirement. The work of the EEGer is greatly simplified by the fact that the EEG tracing is reduced to the 'interesting' sections only. This was originally possible because of the concept developed by Ives et al. (1976) of delaying the EEG so that activity prior to perceptible clinical signs were always retained. The automatic detection of interictal spikes and seizures in the EEG complemented very effectively this original method of seizure recording. Video recording plays a critical role in the evaluation of seizure disorders. In order to have the maximum quality of EEG and behavior, we record them on their most appropriate medium, paper and video tape respectively; the two are synchronized by a common clock. EEGs are also recorded on a computer tape or disk and can be further analyzed for clinical and research purposes.
Canada↗
Pathophysiology of generalized photosensitive epilepsy in the cat.
Feline generalized penicillin-induced epilepsy is a reliable experimental model of epileptic photosensitivity. Binocular photic stimulation at 4-8 flashes/s consistently triggers generalized, bilaterally synchronous spike-and-wave discharges in cats submitted to long-term intramuscular penicillin administration at low dosage (50,000-150,000 IU/kg). The photically induced epileptic activity is first and mainly recorded from the cerebral cortex as compared with the lateral geniculate (GL) body, therefore supporting a cortical onset of epileptic photosensitivity. At this low penicillin dosage, only minimal spontaneous spike-and-wave activity is recorded. Bilateral GL stimulation is more effective than binocular photic stimulation in triggering spike-and-wave discharges, whereas unilateral GL stimulation is grossly ineffective. This observation implies a role of bilateral specific visual thalamocortical volleys in the genesis of epileptic photosensitivity. Five of 12 randomly selected cats receiving long-term penicillin exhibited spontaneous epileptic photosensitivity, a finding that suggests an underlying genetic predisposition of the feline species to this condition.
Animals↗
Assessment of cortical dopaminergic activity in Parkinson's disease by EEG.
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Adult↗
The indications for and the role of depth electrode recording in epilepsy.
A series of 47 patients studied with stereotactically implanted depth electrodes is analyzed. Indications and grouping of the patients fall into three main categories: (a) the bitemporal series (35 patients) where there is ambiguity as to the lateralization of the focus; (b) the unilateral series (6 patients) where the problem is one of localization within one hemisphere, and (c) the generalized series where one tries to determine the primary focus in secondary generalized seizures (6 patients). The best indication appears to be the bitemporal cases, in which a large number of attacks can be recorded by computer. Most of them tend to have a well-lateralized onset in one of the temporal lobes; 32 of the 35 implanted patients were operated upon (91.4%). The results on the seizure tendency in these patients is comparable, if not superior, to those obtained in the so-called unilateral cases. Correlation studies indicate that interictal activity is a good indicator of the predominance of seizures.
Adolescent↗
The role of the limbic system in experiential phenomena of temporal lobe epilepsy.
Experiential phenomena occurring in spontaneous seizures or evoked by brain stimulation were reported by 18 of 29 patients with medically intractable temporal lobe epilepsy who were investigated with chronic, stereotaxically implanted intracerebral electrodes. The phenomena mainly consisted of perceptual (visual or auditory) hallucinations or illusions, memory flashbacks, illusions of familiarity, forced thinking, or emotions. Experiential phenomena did not occur unless a seizure discharge or electrical stimulation involved limbic structures. For such phenomena to occur, seizure discharge or electrical stimulation did not have to implicate temporal neocortex. This was true even for perceptual experiential phenomena. Many experiential responses elicited by electrical stimulation, particularly when applied to the amygdala, were not associated with electrical afterdischarge. Limbic activation by seizure discharge or electrical stimulation may add an affective dimension to perceptual and mnemonic data processed by the temporal neocortex, which may be required for endowing them with experiential immediacy.
Adult↗
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↗
Dopaminergic mechanism in generalized photosensitive epilepsy.
Apomorphine, a dopamine receptor agonist, blocked epileptic photosensitivity in patients with primary corticoreticular epilepsy. This effect was not modified by naloxone, a narcotic antagonist, suggesting that apomorphine acts on cerebral dopaminergic receptors. Apomorphine did not block spontaneous spike-and-wave discharges in patients with nonphotosensitive primary corticoreticular epilepsy. The different actions of apomorphine on spontaneous and photically induced spike-and-wave activity suggest that there is a selective dopaminergic mechanism in human epileptic photosensitivity.
Adolescent↗
Startle disease or hyperekplexia: further delineation of the syndrome.
Startle disease is an autosomal dominant disorder with two phenotypic expressions. In the major form, there is hypertonia in infancy, and later an insecure gait. The patients have falling attacks without unconsciousness and in these, they are often injured or suffer concussions. Episodes of shaking of the limbs lasting for several minutes and resembling generalized clonus or repetitive myoclonus occur. These are most often nocturnal and are also unaccompanied by loss of consciousness. the patients are hyperreflexic and show an increased incidence of associated neurological and electroencephalographic abnormalities. The minor form of startle disease is only manifested by excessive startle and this is inconstant. In infancy it is brought out by febrile illness and in adult life by emotional stress. Gastaut and Villeneuve postulated the existence of a sporadic form of hyperekplexia different from the disorder described by Suhren et al. Review of their report and comparison with the cases of Suhren et al, and our own patients leads us to believe that the sporadic and familial forms of startle disease are the same. The disorder is rare, probably misdiagnosed initially as spastic quadriplegia, and later as epilepsy. Clonazepam appears to be the treatment of choice and its effect is sustained.
Adolescent↗
Diagnosis of hysterical seizures in epileptic patients.
The coexistence of epileptic and hysterical seizures in the same patient is not rare and creates problems in diagnosis and management. The authors used simultaneous video-EEG monitoring to document the diagnosis of hysterical seizures in 9 epileptic patients; clear-cut hysterical seizures were seen in all 9. The authors used individualized re-educative psychotherapy to teach patients alternative coping techniques and discharged them on minimum dosages of anticonvulsants. None of the patients had a classical hysterical personality, which suggests that conversion reaction is a more appropriate diagnosis, The etiology of "hysterical" seizures varies; the authors emphasize individualized treatment and long-term follow-up.
Adolescent↗
Transient abolition of generalized photosensitive epileptic discharge in humans by apomorphine, a dopamine-receptor agonist.
Apomorphine, an agonist of dopamine receptors, blocks or significantly reduces photically induced seizures in the baboon (Papio papio). We therefore studied the effect of subcutaneously administered apomorphine in 11 patients with generalized photosensitive epilepsy. Visual evoked potentials were not altered by apomorphine, but in nine patients apomorphine transiently blocked the epileptic photosensitivity for an average of 45 minutes. Therefore, dopaminergic mechanisms play a role in the pathophysiology of human generalized photosensitive epilepsy.
Adolescent↗