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Biomedical subjects

L F Quesney

Publications and source records attributed to L F Quesney.

At least 37 records · Page 2Linked to original sources
PubMed1993

Increased neocortical spiking and surgical outcome after selective amygdalo-hippocampectomy.

We studied the electrocorticogram (ECoG) before and immediately after transcortical selective amygdalo-hippocampectomy, prospectively in 13 consecutive patients and retrospectively in three others. ECoG was performed with surface and two depth electrodes inserted through T2 aimed at the amygdala and anterior hippocampus. Before resection the ECoG showed a variable amount of interictal spiking, recorded either independently from the depth and surface, or synchronously. A small cortical incision (2-3 cm) was made in T2. The hippocampus, amygdala and parahippocampal gyrus were removed subpially. After the resection, increased epileptiform abnormality was observed in all 16 patients and a different ECoG pattern emerged. It consisted of repetitive, high amplitude spikes and polyspikes, separated by attenuated background, recorded from the most anterior temporal area. Similar observations were reported by Niemeyer in 1958. The outcome was comparable to that of standard anterior temporal resection: 62.5% class I and 25% class II (Engel's scale). ECoG is often used to tailor the amount of resection, and the persistence of epileptic abnormalities correlates with worse outcome. This is not the case in selective amygdalo-hippocampectomy, suggesting that a different underlying mechanism is responsible for the increased interictal spiking following this procedure.

Adolescent↗
PubMed1993

The human dorsal hippocampal commissure. An anatomically identifiable and functional pathway.

The hippocampal commissural system in the human brain was found to be similar to that of non-human primates. Three normal serially sectioned human brains were studied in coronal and sagittal sections. Morphological criteria that had been validated in experimental studies on the hippocampal commissures in monkeys (Amaral et al., 1984; Demeter et al., 1985; Lamantia and Rakic, 1990) were applied to the study of these human brains. It was found that while a further reduction in the ventral hippocampal commissure has taken place in human phylogeny leading to its near or total disappearance, the dorsal hippocampal commissure is well developed and represents a sizable fibre tract. It crosses the midline under the rostral portion of the splenium and the caudal part of the body of the corpus callosum. Its fibres as they travel between the splenium and the hippocampal formation attach themselves to the fornix and the inferior portion of the forceps major of the corpus callosum. In its morphology the human dorsal hippocampal commissure fully conforms to that reported in experimental tracer studies in the monkey (Amaral et al., 1984; Demeter et al., 1985). Depth electrode EEG recordings of temporal lobe seizures show, in some instances, a pattern of contralateral spread which strongly suggests that it occurred through the dorsal hippocampal commissure. This statement is based on a careful analysis of the different patterns of contralateral spread of seizure discharge in the light of the known anatomical connections of mesial temporal structures through both direct commissural pathways and through possible indirect ones involving subcortical structures or the frontal lobe. For seizure discharges originating in mesial temporal structures of one side with spread to the contralateral hippocampus before any involvement of the contralateral isocortex the dorsal hippocampal commissure is the only likely pathway of contralateral propagation. Alternative routes appear unlikely in the light of the known primate anatomy of the commissural and other connections of the temporal lobe. Thus humans, despite claims to the contrary (Wilson et al., 1987, 1990, 1991), seem to possess a functional dorsal hippocampal commissure. Some patterns of seizure spread observed in this study which seem to utilize the dorsal hippocampal commissure may be relevant for two phenomena that are of clinical interest: (i) pure amnestic seizures (Palmini et al., 1992); (ii) false lateralization of seizure onset in extracranial EEG recordings in the type III of contralateral seizure spread as defined in this study.

Adolescent↗
PubMed1992

Occipital lobe epilepsy: electroclinical manifestations, electrocorticography, cortical stimulation and outcome in 42 patients treated between 1930 and 1991. Surgery of occipital lobe epilepsy.

Our study documents the clinical and electrographic findings in 42 patients with medically refractory occipital lobe epilepsy, who underwent surgery at the Montreal Neurological Institute between 1930 and 1991, and the evolving manner in which those patients were studied by successive generations of investigators. In more than two-thirds of the patients the clinical manifestations indicated the occipital onset of the seizures. Seventy-three percent experienced visual aurae, of which elementary hallucinations were the most common and 12 also had ictal blindness. Other occipital manifestations included: contralateral eye deviation, blinking, a sensation of eye movement and nystagmoid eye movements. Intra-operative cortical stimulation elicited a habitual aura in 37% of 29 patients. Lateralizing clinical features were seen in almost two-thirds of patients: contralateral head deviation occurred in half, 59% had visual field defects contralateral to the epileptogenic area and 64% had abnormal imaging studies ipsilateral to the side of surgery. More than one-third of patients exhibited more than one seizure type, suggesting ictal spread to temporal or frontal lobe: 50% had typical temporal lobe automatisms, and 38% exhibited focal motor seizure activity. Surface electroencephalogram (EEG) recordings showed posterior temporal-occipital epileptiform discharges in 46% of patients. Only 18% had electronegative spiking limited to 01 or 02. Large epileptogenic areas were often found on intracranial recording with depth electrodes and on electrocorticography. Pre-excision electrocorticography spiking was restricted to the occipital lobe in only 13 out of 34 patients. More often spiking also involved the posterior temporal and posterior parietal regions. Twenty-three patients underwent only occipital resections; five had only temporal resections, so as to preserve the visual fields, and the remaining 14 patients had extensive resections, which included the posterior temporal or posterior parietal regions. A follow-up period of 1 to 46 yrs (mean 17 yrs) was available for 37 patients. Forty-six percent became seizure free and 21% had a significant reduction in seizure frequency. A better outcome was observed in those patients in whom there was no post-resection electrocorticographic or surface EEG epileptiform discharge, or who exhibited an occipital lobe lesion.

Adolescent↗
PubMed1992

Extratemporal epilepsy: clinical presentation, pre-operative EEG localization and surgical outcome.

To summarize, the most commonly encountered problems in the pre-operative EEG localization of the epileptogenic zone in patients with extra-temporal epilepsy are dependent upon: 1) Poor EEG localization of the interictal epileptic abnormality and poor localization of seizure onset. 2) Presence of a widespread epileptogenic area during interictal and ictal tracings, often involving two or more lobes synchronously or independently, thus suggesting a multilobar or a multifocal epileptic disorder. 3) Absence or paucity of interictal epileptiform discharges is not an uncommon finding and clinical seizures without accompanying ictal EEG manifestations are also not uncommon. 4) Different paths of seizure propagation might occur even in individual patients. This may reflect clinically as different seizure patterns resembling a multifocal seizure problem. From this review, one could envisage that the future research challenge in extra-temporal epilepsy resides in the development of a technology or system which will provide a better localization of the seizure generator, as well as a better identification of the mechanisms of seizure spread, ideally indicating anatomical pathways involved.

Electroencephalography↗
PubMed1992

Presurgical EEG investigation in frontal lobe epilepsy.

Poor localization of the interictal epileptic abnormality and the rather unreliable EEG localization of ictal onsets in patients with frontal lobe epilepsy may be due to some of the following factors: (1) high risk of EEG sampling error, (2) early seizure spread within and outside the frontal lobe, (3) widespread distribution of the epileptogenic brain tissue responsible for the patient's habitual seizures, and (4) secondary bilateral synchrony and secondary epileptogenesis. The relevance of these factors in the preoperative investigation of patients with frontal lobe epilepsy was studied in: (a) 34 adult patients (mean age: 25 years) who became and persisted seizure free after restrictive surgical removal of the anterofrontal region, the parasagittal region convexity or the fronto-opercular area; (b) 12 patients in whom the pre-operative EEG investigation with extracranial electrodes failed to localize the site of seizure onset, leading to further investigation with depth electrodes.

Adult↗
PubMed1991

Preoperative electroencephalographic investigation in frontal lobe epilepsy: electroencephalographic and electrocorticographic recordings.

The first section of this article deals with specific anatomic and pathophysiologic factors which contribute to a poor EEG localization of the interictal epileptic abnormality and to the unreliable seizure onset localization commonly reported in patients with frontal lobe epilepsy. The localizing effectiveness of long term EEG monitoring was reviewed in four different groups of frontal lobe epileptic patients who underwent preoperative EEG investigation with extracranial and intracranial electrodes. The results of this study reveal a continuum distribution of interictal epileptic disturbances, ranging from focal abnormalities to lobar or multi-lobar epileptogenesis. A frontal lobe localization of the seizure generator based on ictal recordings obtained with extracranial electrodes is rather poor and much more reliable results can be obtained by depth-electroencephalography.

Adolescent↗
PubMed1991

Electrocorticography in temporal lobe epilepsy surgery.

The results of intra-operative cortical EEG recordings (ECoG) were assessed in 30 patients with medically refractory complex partial seizures submitted to temporal lobectomy. Interictal spiking was most frequently recorded from mesial temporal lobe structures (amygdaloid-hippocampal region) and from the temporal neocortex synchronously, as observed in 21/30 patients. In 7 patients, the interictal spiking involved the temporal neocortex exclusively. Electrical stimulation of mesial temporal lobe structures reproduced the patient's habitual warning in 10 patients. The results of this study confirms that ECoG provides reliable intra-operative mapping of the epileptogenic brain tissue to be excised.

Adolescent↗
PubMed1991

Functional hemispherectomy: EEG findings, spiking from isolated brain postoperatively, and prediction of outcome.

We reviewed the prognostic significance of preoperative EEG findings in 25 patients who underwent functional hemispherectomy. Bilateral independent epileptogenic foci, found in five patients, generally indicate a less satisfactory outcome, with only three of the five patients becoming seizure free following hemispherectomy. In contrast, abnormalities of background activity over the "good" hemisphere, multifocal epileptic activity confined to the side of operation, or bilaterally synchronous discharges were associated with a good outcome and should not be considered as contraindications to operation. Postoperatively, discharges may occur in the functionally isolated frontal and occipital cortex, which are benign, with no other clinical significance than showing that the isolated cortex remains viable and continues to generate epileptogenic potentials.

Action Potentials↗
PubMed1990

The clinical differentiation of seizures arising in the parasagittal and anterolaterodorsal frontal convexities.

The ictal clinical manifestations of 40 patients with frontal lobe epilepsy who became and remained seizure free after selective removal of the parasagittal or anterolaterodorsal convexities were studied. Seizures arising from the parasagittal region were characterized by a high incidence of somatosensory auras (60%) and by tonic and/or clonic motor behavior (100%) and never exhibited automatisms. Conversely, the anterolaterodorsal convexity group never showed somatosensory auras but often had warnings more typical of temporal lobe seizures, only displayed partial motor seizure activity in half the cases, and included a relatively high incidence of automatisms (30%). These clinical differences may be useful in the localization of frontal lobe epileptogenic foci. The manifestations of anterolaterodorsal convexity seizures may reflect frequent spread to the temporal lobe, whereas parasagittal convexity seizures often show initial ictal behavior, in keeping with seizure activity in that region. Early ictal unilateral head turning without other motor manifestations was seen in 3 of 10 patients in the parasagittal convexity group and in 9 of 30 patients in the anterolaterodorsal convexity group. In 11 of these 12 cases, the head turning was contralateral to the surgical removal.

Adolescent↗
PubMed1990

Common dopaminergic mechanism for epileptic photosensitivity in progressive myoclonus epilepsies.

We studied the effect of apomorphine, a dopamine receptor agonist, on epileptic photosensitivity in 7 patients with progressive myoclonus epilepsy (PME). Specific diagnoses included Baltic PME (Unverricht-Lundborg disease), Lafora disease, Kufs' disease, juvenile neuroaxonal dystrophy, and action myoclonus-renal failure syndrome; 2 patients had PME of uncertain etiology. Apomorphine blocked the epileptic photosensitivity in all patients and also reduced intention myoclonus in a patient with Baltic PME. There is a common deficit of dopaminergic inhibitory neurotransmission at the level of the striate cortex in patients with PME, regardless of the nature of the specific underlying neuropathologic process.

Adolescent↗
PubMed1989

Depth electrode investigations in patients with bitemporal epileptiform abnormalities.

Fifty-seven patients showing bitemporal independent epileptiform abnormalities on extracranial electroencephalograms (EEGs) in whom the epileptogenic zone could not be localized or lateralized by extracranial EEG and other noninvasive tests were investigated with stereotactic depth electrode recordings. In a majority of 44 patients (77%), seizures originated exclusively or with a strong predominance in one temporal lobe only. Of the remaining 13 patients (23%), 8 had seizures originating independently in either temporal lobe without significant lateralized predominance, and 5 had multiple seizure patterns, which were often diffuse. The patterns of seizure onset as recorded by depth electrodes tended to vary even in the same patient. Electrical stimulation studies and the determination of afterdischarge thresholds were of limited utility for lateralization of seizure onset.

Adolescent↗
PubMed1989

Results of surgical treatment in patients with bitemporal epileptiform abnormalities.

Fifty-three of 57 patients who had evidence of bitemporal epileptiform abnormalities and who required investigation with stereotactic depth electroencephalography (SDEEG) recordings to determine the site of origin of seizures underwent surgical resection for the treatment of their epilepsy. A minimum of 2 years' follow-up was available in 48 patients who underwent a temporal lobe resection. In this group, 19 patients (40%) were greatly improved, and of these 14 (29%) became seizure free and 5 (10%) had no more than 3 seizures each year. Another 22 patients (46%) showed a worthwhile reduction in seizure frequency of at least 50%. Seven patients (15%) were not significantly improved. An etiological factor of early convulsions before age 3 (usually febrile) was associated with a better outcome. Both the lack of a strong predominance for SDEEG-recorded seizures to arise in the resected temporal lobe and the presence of residual epileptiform abnormalities in the postexcision electrocorticogram were correlated with poorer results.

Adult↗
PubMed1989

Myoclonus epilepsy and ragged-red fibres (MERRF). 2. Electrophysiological studies and comparison with other progressive myoclonus epilepsies.

Electrophysiological studies (EEG, evoked potentials, nerve conduction and EMG) in 13 patients with myoclonus epilepsy with ragged red fibres (MERRF) are presented. The most notable findings are the presence of atypical irregular generalized spike and wave discharges arising from an abnormal EEG background (9 patients), focal epileptiform abnormalities (6 patients) most commonly over the occipital regions and giant cortical SEPs (4 of 6 patients tested). Similar findings of disturbed EEG background activity, generalized spike and wave discharges and giant cortical SEPs appear to be shared by the group of diseases characterized by progressive myoclonus epilepsy.

Adolescent↗
PubMed1988

Functional hemispherectomy for treatment of epilepsy associated with hemiplegia: rationale, indications, results, and comparison with callosotomy.

Hemispherectomy is effective in arresting seizures associated with maximal or near maximal hemiparesis. This procedure, however, carries an unacceptable 33% risk of late complications due to cerebral hemosiderosis. Anatomically partial but functionally complete hemispherectomy was devised to avoid these complications. The frontal or occipital lobes, or both, were left in place with the blood supply intact but with connections to commissures and brainstem divided. The central strip and parietal and temporal lobes were removed. Twenty patients were so treated with a follow-up of 4 to 13 years (average, 7.3 years) in 14. Ten of these are seizure free, 1 had a single nocturnal seizure, 1 had occasional focal twitching, and 2 had a worthwhile but lesser reduction in the seizure tendency. None has developed cerebral hemosiderosis, to date. In appropriately selected patients, functional hemispherectomy is an effective procedure preferable to callosotomy or to partial hemispherectomy. When there is no independent ictal discharge from the opposite hemisphere, arrest of seizures may be expected, leading to improvement in cognitive functioning (mean increase, 10 IQ points), social behavior, and a reduction in or discontinuation of anticonvulsant medication. In these patients, gait and hand use remain unchanged.

Adolescent↗