Multiple subpial transection in kainic acid-induced focal cortical seizure

Circumscribing Laser Cuts Attenuate Seizure Propagation in a Mouse Model of Focal Epilepsy

In partial onset epilepsy, seizures arise focally in the brain and often propagate. Patients frequently become refractory to medical management, leaving neurosurgery, which can cause neurologic deficits, as a primary treatment. In the cortex, focal seizures spread through horizontal connections in layers II/III, suggesting that severing these connections can block seizures while preserving function. Focal neocortical epilepsy is induced in mice, sub-surface cuts are created surrounding the seizure focus using tightly-focused femtosecond laser pulses, and electrophysiological recordings are acquired at multiple locations for 3-12 months. Cuts reduced seizure frequency in most animals by 87%, and only 5% of remaining seizures propagated to the distant electrodes, compared to 80% in control animals. These cuts produced a modest decrease in cortical blood flow that recovered and left a ≈20-µm wide scar with minimal collateral damage. When placed over the motor cortex, cuts do not cause notable deficits in a skilled reaching task, suggesting they hold promise as a novel neurosurgical approach for intractable focal cortical epilepsy.

A new model of experimental hemispherotomy in young adult Rattus norvegicus: a neural tract tracing and SPECT in vivo study

OBJECTIVE

The objective of this study was to describe a new experimental model of hemispherotomy performed on laboratory animals.

METHODS

Twenty-six male young adult Wistar rats were distributed into two groups (surgery and control). The nonfluorescent anterograde neurotracer biotinylated dextran amine (BDA; 10,000 MW) was microinjected into the motor cortex area (M1) according to The Rat Brain in Stereotaxic Coordinates atlas to identify pathways and fibers disconnected after the experimental hemispherectomy. SPECT tomographic images of 99mTc hexamethylpropyleneamine oxime were obtained to verify perfusion in functioning areas of the disconnected and intact brain. A reproducible and validated surgical procedure is described in detail, including exact measurements and anatomical relationships. An additional 30 rodents (n = 10 rats per group) were divided into naïve, sham, and hemispherotomy groups and underwent the rotarod test.

RESULTS

Cortico-cortical neural pathways were identified crossing the midline and contacting neuronal perikarya in the contralateral brain hemisphere in controls, but not in animals undergoing hemispherotomy. There was an absence of perfusion in the left side of the brain of the animals undergoing hemispherotomy. Motor performance was significantly affected by brain injuries, increasing the number of attempts to maintain balance on the moving cylinder in the rotarod test at 10 and 30 days after the hemispherotomy, with a tendency to minimize the motor performance deficit over time.

CONCLUSIONS

The present findings show that the technique reproduced neural disconnection with minimal resection of brain parenchyma in young adult rats, thereby duplicating the hemispherotomy procedures in human patients.

Rat sensorimotor cortex tolerance to parallel transections induced by synchrotron-generated X-ray microbeams

Microbeam radiation therapy is a novel preclinical technique, which uses synchrotron-generated X-rays for the treatment of brain tumours and drug-resistant epilepsies. In order to safely translate this approach to humans, a more in-depth knowledge of the long-term radiobiology of microbeams in healthy tissues is required. We report here the result of the characterization of the rat sensorimotor cortex tolerance to microradiosurgical parallel transections. Healthy adult male Wistar rats underwent irradiation with arrays of parallel microbeams. Beam thickness, spacing and incident dose were 100 or 600 µm, 400 or 1200 µm and 360 or 150 Gy, respectively. Motor performance was carried over a 3-month period. Three months after irradiation rats were sacrificed to evaluate the effects of irradiation on brain tissues by histology and immunohistochemistry. Microbeam irradiation of sensorimotor cortex did not affect weight gain and motor performance. No gross signs of paralysis or paresis were also observed. The cortical architecture was not altered, despite the presence of cell death along the irradiation path. Reactive gliosis was evident in the microbeam path of rats irradiated with 150 Gy, whereas no increase was observed in rats irradiated with 360 Gy.

Treatment of epilepsy with bipolar electro-coagulation: an analysis of cortical blood flow and histological change in temporal lobe

BACKGROUND

Bipolar electro-coagulation has a reported efficacy in treating epilepsy involving functional cortex by pure electro-coagulation or combination with resection. However, the mechanisms of bipolar electro-coagulation are not completely known. We studied the acute cortical blood flow and histological changes after bipolar electro-coagulation in 24 patients with intractable temporal lobe epilepsy.

METHODS

Twenty-four patients were consecutively enrolled, and divided into three groups according to the date of admission. The regional cortical blood flow (rCBF), electrocorticography, the depth of cortex damage, and acute histological changes (H and E staining, neuronal staining and neurofilament (NF) staining) were analyzed before and after the operation. The t-test analysis was used to compare the rCBF before and after the operation.

RESULTS

The rCBF after coagulation was significantly reduced (P < 0.05). The spikes were significantly reduced after electro-coagulation. For the temporal cortex, the depth of cortical damage with output power of 2-9 W after electro-coagulation was 0.34 ± 0.03, 0.48 ± 0.06, 0.69 ± 0.06, 0.84 ± 0.09, 0.98 ± 0.08, 1.10 ± 0.11, 1.11 ± 0.09, and 1.22 ± 0.11 mm, respectively. Coagulation with output power of 4-5 W completely damaged the neurons and NF protein in the molecular layer, external granular layer, and external pyramidal layer.

CONCLUSIONS

The electro-coagulation not only destroyed the neurons and NF protein, but also reduced the rCBF. We concluded that the injuries caused by electro-coagulation would prevent horizontal synchronization and spread of epileptic discharges, and partially destroy the epileptic focus.

Synchrotron-generated microbeam sensorimotor cortex transections induce seizure control without disruption of neurological functions

Synchrotron-generated X-ray microplanar beams (microbeams) are characterized by the ability to deliver extremely high doses of radiation to spatially restricted volumes of tissue. Minimal dose spreading outside the beam path provides an exceptional degree of protection from radio-induced damage to the neurons and glia adjacent to the microscopic slices of tissue irradiated. The preservation of cortical architecture following high-dose microbeam irradiation and the ability to induce non-invasively the equivalent of a surgical cut over the cortex is of great interest for the development of novel experimental models in neurobiology and new treatment avenues for a variety of brain disorders. Microbeams (size 100 µm/600 µm, center-to-center distance of 400 µm/1200 µm, peak entrance doses of 360-240 Gy/150-100 Gy) delivered to the sensorimotor cortex of six 2-month-old naïve rats generated histologically evident cortical transections, without modifying motor behavior and weight gain up to 7 months. Microbeam transections of the sensorimotor cortex dramatically reduced convulsive seizure duration in a further group of 12 rats receiving local infusion of kainic acid. No subsequent neurological deficit was associated with the treatment. These data provide a novel tool to study the functions of the cortex and pave the way for the development of new therapeutic strategies for epilepsy and other neurological diseases.

Pure bipolar electro-coagulation on functional cortex in the treatment of epilepsy involving eloquent areas

PURPOSE

Although resection of an epileptogenic region remains the main procedure of epilepsy surgery, epileptogenic areas in functionally critical cortex cannot be approached in that manner. Bipolar electro-coagulation on functional cortex (BCFC) was developed to treat such refractory seizures without causing unacceptable neurological deficits. Here we report the outcome of this therapy.

METHODS

Fifteen patients who underwent pure BCFC without resection between 2002 and 2008 were retrospectively reviewed with regard to seizure outcome, postoperative complications, and predictive factors.

KEY FINDINGS

Seven patients developed hemiparesis after the operation but fully recovered within 1-6 months. One patient developed mild dysphasia, which was resolved within 12 months. All neurological deficits were temporary in the sense that they ultimately did not result in a deficit that would be noticed during a standard clinical examination. There were no subdural hemorrhage and infection. Engel class I outcome was achieved in two (13.3%) patients; class II, in six (40%); class III, in three (20%); and class IV, in four (26.7%).

SIGNIFICANCE

The BCFC technique is only a palliative surgery, and cannot be applied for all epilepsies, however, this therapy proved to be effective when the epileptogenic foci are located in unresectable cortex. BCFC is safe and easy to use.

Effective suppression of hippocampal seizures in rats by direct hippocampal cooling with a Peltier chip

OBJECT

The use of focal brain cooling to eliminate epileptic discharges (EDs) has attracted increasing attention in the scientific community. In this study, the inhibitory effect of selective hippocampal cooling on experimental hippocampal seizures was investigated using a newly devised cooling system with a thermoelectric (Peltier) chip.

METHODS

A copper needle coated with silicone and attached to the Peltier chip was used for the cooling device. The experiments were performed first in a phantom model with thermography and second in adult male Sprague-Dawley rats in a state of halothane anesthesia. The cooling needle, a thermocouple, and a needle electrode for electroencephalography recording were inserted into the right hippocampus. Kainic acid (KA) was injected into the right hippocampus to provoke the EDs. The animals were divided into hippocampal cooling (10 rats) and noncooling (control, 10 rats) groups.

RESULTS

In the phantom study, the cooling effects (9 degrees C) occurred in the spherical areas around the needle tip. In the rats the temperature of the cooled hippocampus decreased below 20 degrees C within a 1.6-mm radius and below 25 degrees C within a 2.4-mm radius from the cooling center. The temperature at the needle tip decreased below 20 degrees C within 1 minute and was maintained at the same level until the end of the cooling process. The amplitude of the EDs was suppressed to 68.1 +/- 4.8% of the precooling value and remained low thereafter. No histological damage due to cooling was observed in the rat hippocampus.

CONCLUSIONS

Selective hippocampal cooling effectively suppresses the KA-induced hippocampal EDs. Direct hippocampal cooling with a permanently implantable system is potentially useful as a minimally invasive therapy for temporal lobe epilepsy and therefore could be an alternative to the temporal lobectomy.

[Animal models to develop surgery of focal epilepsies?]

A model is a simplified preparation that reproduces only the most critical features of a disease. To be considered as a validated animal model, such an experimental preparation must fulfill three criteria: isomorphism or similarities of the symptoms; predictivity or identical pharmacological reactivity; homology or etiological similarity. In epilepsy, the use of animal models helps our understanding of physiological and pathological networks involved in the genesis, maintenance, and propagation of seizures. The animal models of epilepsy are also useful in designing and testing new surgical therapeutical strategies, in particular using deconnection or neuromodulation in drug-resistant focal epilepsies. Here we describe three animal models of focal epilepsy, adapted to addressing experimental surgery issues. Kindling consists in the regular liminar stimulation of a given brain structure in the rodent to develop a focal discharge that is secondarily generalized. The local application of epileptogenic agents such as cobalt, iron, or penicillin leads to focal discharges that do not generalize in the rodent or the primate. It is a model of focal neocortical epilepsy without secondary generalization. The focal application of kainate, an excitotoxic glutamate agonist, in the dorsal hippocampus of the adult mouse results, after a latent period, in spontaneous and recurrent focal discharges, behavioral interictal troubles, drug resistance, and histological anomalies reminiscent of hippocampal sclerosis. This constitutes a model of mesial-temporal epilepsy. Better knowledge, in these models, of the neural networks generating, propagating, and/or controlling the seizures should make it possible to design innovative surgical approaches for the treatment of drug-resistant epilepsies.

The effect of electrical stimulation and lesioning of the anterior thalamic nucleus on kainic acid-induced focal cortical seizure status in rats

PURPOSE

The present study aimed to clarify the effect of electrical stimulation and lesioning of the anterior nucleus of the thalamus (ANT) on kainic acid (KA)-induced focal cortical seizures in a rat model. To address the mechanism underlying these anticonvulsant actions, cerebral glucose metabolism after ANT electrical stimulation and lesioning was also examined.

METHODS

Wistar rats were divided into five major groups: control (n = 9), unilateral (n = 9), and bilateral (n = 9) ANT electrical stimulation, and unilateral (n = 9) and bilateral (n = 9) ANT lesioning. After KA injection, average clinical-seizure frequencies in each group were measured. Electrical stimulation of ANT was introduced after induction of seizure status epilepticus. Stimulation was on for 30 min and off for 30 min per 60-min cycle. Local cerebral glucose utilization (LCGU) was also measured by using [(14)C] 2-deoxyglucose autoradiography in three groups of rats: control (n = 7), bilateral ANT stimulation (n = 7), and bilateral ANT lesioning (n = 7).

RESULTS

Unilateral ANT electrical stimulation and lesioning significantly reduced clinical seizure frequency, compared with control animals. Strikingly, no animals treated with bilateral ANT procedures demonstrated any clinical seizure. LCGU was markedly increased in the sensorimotor cortex, striatum, thalamus, mammillary body, and midbrain tegmentum of control group rats after KA injection, but no increase in LCGU was noted in rats treated with bilateral ANT lesioning or stimulation.

CONCLUSIONS

The electrical stimulation and lesioning of ANT suppressed focal cortical clinical seizures induced by KA injection. Additionally, an analysis of cerebral metabolic changes indicated that these procedures might suppress the function as amplifier and synchronizer of seizure activity.

Multiple subpial transections in pediatric epilepsy: indications and outcomes

OBJECTIVE

Multiple subpial transection (MST) is a surgical technique mainly used when epileptiform activity arises from eloquent or functional brain cortex. In the medical literature, there are relatively few studies reporting the efficacy and safety of this procedure in adults and in children. We review the scientific rationale, the indications, and the results of this procedure.

METHODS

Neuroanatomic studies show that the basic functional cortical unit is arranged vertically, and epileptic activity spreads horizontally. Minimal cortical unit is essential for maintenance of cortical activity. Vertical incisions in the cortex interrupt transverse synaptic connections, preventing seizure propagation while preserving the vertical column subserving neuronal function. In the past, it has been difficult to assess the efficacy of MSTs per se, as they have usually been performed together with cortical resection or lesionectomy. After MSTs, studies show that 33-46% of treated children are in Engel class I or II. The permanent complication rate is low with no permanent language or motor disabilities.

CONCLUSIONS

MST is a safe procedure with unclear specific efficacy. It has been used mainly in conjunction with cortical resection or lesionectomy, when the eloquent cortex is involved in the seizure activity. Further prospective studies are needed to define the role of MST in epilepsy surgery.

Use of a Peltier chip with a newly devised local brain–cooling system for neocortical seizures in the rat

✓ Local cortical cooling for termination of epileptic discharges (EDs) has recently become a focus of research. The authors report on a newly devised cooling system that uses a thermoelectric (Peltier) chip and examine the system’s performance in experimental neocortical seizures. Experiments were performed in adult male Sprague–Dawley rats after induction of halothane anesthesia. The Peltier chip was attached to a heat sink with a water channel. Two silicon tubes were connected to the heat sink, and water at 37°C was circulated in the channel. The newly designed device was placed on the surface of the cortex. Kainic acid (KA) was injected into the cortex to provoke EDs. In the nonepileptic cortex, the temperature of the cortical surface decreased to 14.8 ± 1.5°C and that 2 mm below the surface to 27.1 ± 3.1°C within 30 seconds after the start of cooling. The temperature of the heated side of the chip was maintained at approximately 36.9°C. Without water circulation, the temperature of the cortical surface decreased to 20°C but soon began to increase, peaking at 30°C. The temperature of the heated side of the chip rose to more than 60°C. The EDs, which appeared within 20 minutes after KA injection, began to decrease in amplitude immediately after cooling began and continued to decrease as the temperature of the cortex was lowered. Sufficient miniaturization and good performance of the cooling device was demonstrated. Further efforts to develop implantable cooling systems and improve existing ones should be continued.

Clinical application of experimental cortical dysplasia in rats

This report details clinical and experimental studies of focal cortical dysplasia. The first part deals with 14 surgical cases of children with intractable epilepsy. At surgery, intraoperative electrocorticography was performed to localize the epileptic foci under neuroleptanalgesia. Thirteen patients showed epileptiform discharges on this preresection electrocorticography. All foci in noneloquent areas were resected. Patients who had undergone total lesionectomy with complete focus resection showed the most favorable postoperative results. However, the positive correlation between the intraoperative electrocorticographic findings and the pathologic classification of cortical dysplasia was not found in the present study. Nine patients have been seizure free with reduced medication and two patients have achieved worthwhile improvement. We conclude that intraoperative electrocorticography can improve the surgical outcome for intractable epilepsy by localizing epileptic foci for resection. The second part describes a kainic acid-induced experimental model of focal cortical dysplasia, which demonstrated not only the epileptic properties of the dysplasia but also the perilesional epileptogenicity. The findings supported the surgical results for the patients with focal cortical dysplasia.

Long-lasting anticonvulsant effect of focal cooling on experimental neocortical seizures

PURPOSE

Previous clinical and experimental observations have demonstrated that cooling the brain can rapidly terminate focal seizures. We wished to determine whether cooling at regular intervals could prevent or attenuate the development of seizures in a model of focal epilepsy.

METHODS

We induced focal neocortical seizures in halothane-anesthetized rats by the microinjection of 4-aminopyridine (4-AP) into the motor cortex. With a small thermoelectric device, the site of the 4-AP injection was either cooled intermittently (PostCool) for 30 s every 2 min, starting 15 min after the 4-AP injection, or precooled (PreCool) for 30 min before 4-AP injection, by using the same 30-s cooling cycle. Seizures were quantified in 30-min observation periods for 1.5 h.

RESULTS

The average durations of PostCool and PreCool seizures were shorter than those of controls (p < 0.001). In addition, total seizure duration was significantly reduced in both groups, compared with controls (p < 0.01). The ratio of the root mean square power during a seizure to power in the immediate preseizure period was reduced in both PostCool and PreCool groups (p < 0.001). The number of seizures significantly declined over a 30- to 60-min period in both experimental groups, and by 60 min, no seizures were evident.

CONCLUSIONS

These experiments show that gentle cooling to 20 degrees C is capable of markedly reducing subsequent seizure frequency and intensity. The effects in our model, which generates very frequent and intense ictal activity, were robust, suggesting that prophylactic cooling might be even more beneficial in clinical situations. The physiologic mechanism for this preventive effect requires elucidation.

Pathophysiology and functional consequences of human partial epilepsy: lessons from positron emission tomography studies

Positron emission tomography (PET) is a powerful clinical and research tool that, in the past two decades, has provided a great amount of novel data on the pathophysiology and functional consequences of human epilepsy. PET studies revealed cortical and subcortical brain dysfunction of a widespread brain circuitry, providing an unprecedented insight in the complex functional abnormalities of the epileptic brain. Correlation of metabolic and neuroreceptor PET abnormalities with electroclinical variables helped identify parts of this circuitry, some of which are directly related to primary epileptogenesis, while others, adjacent to or remote from the primary epileptic focus, may be secondary to longstanding epilepsy. PET studies have also provided detailed data on the functional anatomy of cognitive and behavioral abnormalities associated with epilepsy. PET, along with other neuroimaging modalities, can measure longitudinal changes in brain function attributed to chronic seizures as well as therapeutic interventions. This review demonstrates how development of more specific PET tracers and application of multimodality imaging by combining structural and functional neuroimaging with electrophysiological data can further improve our understanding of human partial epilepsy, and helps more effective application of PET in presurgical evaluation of patients with intractable seizures.

Intracerebral temperature alterations associated with focal seizures

Because focal seizures produce an increase in local cerebral metabolism and blood flow, we wanted to determine whether they might lead to changes in brain temperature. We induced focal neocortical seizures by microinjection of 4-aminopyridine (4-AP) into the rat motor cortex. The temperature on the dura immediately over the injection site, or 8 mm away, was measured with a thermocouple and in some experiments relative blood flow was monitored with a laser Doppler probe. In animals that did not receive 4-AP, brain and rectal temperature remained fairly constant at 33.5 and 37.2 degrees C, respectively, over a 2 h monitoring period. In animals treated with 4-AP, brain temperature over the seizure focus rose an average of 0.3 degrees C, within a few seconds of seizure onset, while rectal temperature remained constant. The seizure-induced temperature rise was preceded by an increase in cortical blood flow. The temperature, but not blood flow, was also elevated 8 mm away from the seizure focus. When blood flow was increased independently of neuronal activity, by elevating pCO(2), brain temperature also rose by about 0.3 degrees C. Focal seizures in anesthetized rats produce a small, but statistically significant increase in local brain temperature, as a result of increased blood flow that brings brain temperature closer to body temperature. In humans, seizures could actually cause a reduction in brain temperature, because brain temperature is normally higher than body temperature.

Multiple subpial transections: outcome and complications in 20 patients who did not undergo resection

OBJECT

The authors describe patient characteristics, surgical methods, complications, and outcome over time in a cohort of patients who underwent multiple subpial transection (MST) without concomitant cortical resection.

METHODS

Twenty consecutive patients in whom drug-resistant epilepsy had been diagnosed a mean of 16 +/- 9 years earlier (mean +/- standard deviation [SD]) were treated with MST without cortical resection. The mean follow-up period was 49.3 +/- 18.3 months (mean +/- SD, median 58 months). At 12 months of follow up, two of the 20 patients were Engel Class I, one was Class II, six were Class III, and 11 were Class IV. At latest follow up, one patient was Engel Class I, one was Class II, seven were Class III, and 11 were Class IV. According to an alternative five-tiered classification system, two outcomes were excellent, seven were good, one was fair, nine were poor, and one was worse. Outcome was found to be better in patients with no lesions observed on magnetic resonance (MR) imaging, and worse in those with large MST areas. Outcome had a tendency to change (this occurred in 13 of 20 cases). Five patients (25%) improved and seven (35%) deteriorated in Engel outcome class, and in one (5%) both developments occurred over time. Most outcome class changes occurred before the end of the 2nd year (nine), and four were observed in the 5th year. There where seven transient neurological deficits and four surgical complications. There was no permanent significant morbidity, and there were no deaths.

CONCLUSIONS

Forty-five percent of patients achieved a worthwhile improvement after pure MST, if Engel outcome Class III is deemed a worthwhile improvement. The alternative five-tiered classification resulted in 50% with worthwhile improvement (excellent, good, or fair outcome), 45% with poor, and 5% with worse outcome. Lesions that are detectable on MR imaging, and large MST areas are predictive of worse results. Significant intraoperative problems may arise, but this happens infrequently. There is a notable rate of transient morbidity but the rate of permanent morbidity is not significant.

Neocortical seizure termination by focal cooling: temperature dependence and automated seizure detection

PURPOSE

The therapy for focal neocortical epilepsy remains suboptimal. We have, therefore, worked to develop techniques to cool small regions of the neocortical surface for seizure mapping and, ultimately, for long-term suppression of focal seizures.

METHODS

We induced focal neocortical seizures in halothane-anesthetized rats by the microinjection of 4-aminopyridine (4-AP) into the motor cortex. The dura over the injection site was cooled with a Peltier device, and the temperature at the interface between dura and Peltier was measured with a thermocouple. In some experiments, seizures were automatically detected by a computer program that activated the Peltier device.

RESULTS

Monopolar EEG indicated that our seizures were focal and suppressed when cooling was applied directly over the injection site. The threshold temperature required to observe any reduction in seizure duration was 24 degrees C. The temperature gradient across the cooled neocortex was sharp, with the temperature increasing to 31 degrees C at 4 mm below the Peltier, which was cooled to 20 degrees C. Automatic seizure detection reduced the total seizure duration from 43.4 +/- 33.6 s to 5.6 +/- 5.3 s.

CONCLUSIONS

Cooling terminates neocortical seizures when applied very close to the epileptogenic focus. The threshold for seizure termination (24 degrees C) may be lower than the threshold for termination of normal cortical activity, suggesting that this technique will not dissociate the anticonvulsant effect of cooling from the disruption of normal behavior. However, when coupled with automatic seizure detection, focal cooling remains an attractive option for development as a treatment for focal epilepsy.

HSV-mediated delivery of virally derived anti-apoptotic genes protects the rat hippocampus from damage following excitotoxicity, but not metabolic disruption

Studies utilizing gene delivery to the nervous system indicate that various strategies are protective following acute neurological insults such as seizure and stroke. We have found that inhibitors of apoptosis are protective against excitotoxicity and heat stress but not energetic impairment in vitro. Here we studied the neuroprotective efficacy in vivo of these mediators: viral genes (crmA, p35, gamma34.5 KsBcl-2) that have evolved to suppress suicidal host responses to infection, by inhibiting apoptosis. We investigated these effects by utilizing modified herpes vectors to deliver the anti-apoptotic agents intracerebrally and examined them in the face of excitotoxic and metabolic insults. We found that p35 and gamma34.5 reduced by 45% a hippocampal CA3 lesion caused by kainic acid, while crmA and KsBcl-2 did not. None of the inhibitors protected the dentate gyrus of the hippocampus following 3-acetylpyridine, a hypoglycemia model, but we found crmA to worsen the damage. These data are similar to our results in neuronal cultures where the inhibitors protected against the excitotoxin domoic acid, but not against the metabolic poison, cyanide. Together, the results suggest that inhibitors of various apoptotic elements are capable of protecting under acute insult conditions both in vitro and in vivo, suggesting possible future therapeutic applications.

Focal cooling rapidly terminates experimental neocortical seizures

The efficacy of surgical resection for epilepsy is considerably lower for neocortical epilepsy than for temporal lobe epilepsy. We have explored focal cooling with a thermoelectric (Peltier) device as a potential therapy for neocortical epilepsy. After creating a cranial window in anesthetized rats, we induced seizures by injecting artificial cerebrospinal fluid containing 4-aminopyridine (4-AP), a potassium channel blocker. Within 30 minutes of 4-AP injection, animals developed recurrent seizures (duration 85.7 +/- 26.2 seconds; n = 10 rats) that persisted for 2 hours. When a small Peltier device cooled the exposed cortical surface to 20-25 degrees C at seizure onset, the seizure duration was reduced to 8.4 +/- 5.0 seconds (n = 10 rats; p < 0.001). When the Peltier device was placed close to the cortical surface, but not allowed to make physical contact, there was no effect on seizure duration (104.3 +/- 20.7 seconds; p > 0.05 compared to control). Interestingly, the duration of uncooled seizures was reduced after we allowed the cortex to rewarm from prior cooling. Histological examination of the cortex after cooling has shown no evidence of acute or delayed neuronal injury, and blood pressure and temperature remained stable. It may be possible to use Peltier devices for cortical mapping or, when seizure detection algorithms improve, for chronic seizure control.

Antiepileptic effect of nefiracetam on kainic acid-induced limbic seizure in rats

Nefiracetam is being studied as a novel cognition-enhancing agent; however, it has been suggested from studying its chemical structure that it has a potential anticonvulsive effect. We examined the antiepileptic effect of nefiracetam on kainic acid (KA)-induced seizures. KA was infused into the left basolateral amygdaloid nucleus and focal limbic seizures were induced in 43 male Wistar rats. During status epilepticus, 10, 50, 100 or 200 mg/kg of nefiracetam was intravenously injected. Nefiracetam inhibited KA-induced limbic seizures at doses over 100 mg/kg while it had a sedative effect on the animals. In (14C) deoxyglucose autoradiographic studies, the propagation of seizure-induced hypermetabolic areas was also suppressed dose-dependently. From the results, it was indicated that nefiracetam has an antiepileptic effect and that its application may suppress seizure propagation. Further study is required, whether this agent is available as a novel anticonvulsant.