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.

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.

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.

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.

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.

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.

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.

EEG telemetry with closely spaced electrodes in frontal lobe epilepsy.

The use of additional electrodes (other than standard 10-20 electrodes) has proved to be extremely useful in the investigation of patients with temporal lobe epilepsy. The development of 32- and 64-channel EEG machines, along with the reformatting capabilities of digital EEG has greatly increased the possibilities in the number of electrodes and recording montages. The authors wanted to determine whether the use of closely spaced electrodes designed to increase the coverage of frontocentral regions is of benefit in the investigation of patients with frontocentral epilepsy. Patients investigated for frontocentral epilepsy underwent EEG telemetry with closely spaced electrodes based on the 10-10 nomenclature. Twenty-three patients were studied. An additional 30 minutes was required by technicians to create the montage. Unilateral frontal or frontocentral epileptic abnormalities were observed in 10 patients, independent bifrontal in 5 patients, synchronous bifrontal in 4 patients, and no EEG changes in 4 patients. In no patient did the addition of closely spaced electrodes lead to a change in the classification of the EEG. Closely spaced electrodes did not reveal focal abnormalities, which were not already apparent with 10-20 electrodes, nor did they demonstrate evidence of laterality in bilaterally synchronous discharges.

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.

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.

Role of electrocorticography at surgery for lesion-related frontal lobe epilepsy.

BACKGROUND: The prognostic significance of epileptiform activity (EA) recorded intraoperatively at electrocorticography (ECOG) in patients with lesion-related frontal lobe epilepsy (FLE) is unknown. METHODS: The results of ECOG performed in 22 patients with intractable FLE and a circumscribed frontal lobe structural lesion were compared with postoperative seizure control. Three patients underwent re-operation for a total of 25 cases, 23/25 with post-resection ECOG. Lesions were neoplasms (12), hamartomas (6) and arteriovenous malformations (4). RESULTS: Outcomes were 15/25 Class I, 5/25 Class III and 5/25 Class IV (Engel classification). Class I outcome was associated with pre-excision EA recorded from < or = 2 gyri (p < 0.05) and absence of EA, or EA limited to the resection border, at post-excision ECOG (p < 0.01). Complete lesion excision was highly correlated with Class I outcome (p < 0.001). The most significant correlations were seen when ECOG and lesionectomy variables were considered together: all 12 cases with complete lesionectomy and absent post-excision EA distant to the resection border had Class I outcome (p < 0.00015) and all 13 cases with complete lesionectomy and pre-excision EA recorded from < or = 2 gyri had Class I outcome (p < 0.00005). CONCLUSIONS: Postoperative seizure control in lesion-related FLE is assured in the setting of complete lesion resection with pre-excision EA recorded from < or 2 gyri and no post-excision EA distant to the resection border; complete lesion excision is of paramount importance.