Clinical Science

Kirk Nylen , Sergei Likhodii , Peter A. Abdelmalik , Jasper Clarke , and W. McIntyre Burnham
The ketogenic diet (KD) is a high-fat, low-carbohydrate, and adequate-protein diet used to treat drug-resistant seizures. It is currently unknown exactly how the KD exerts its anticonvulsant effects. Animal models are used to study the KD anticonvulsant mechanism of action. In the present study, we explored the ability of two KDs, a 4:1 KD and a 6.3:1 KD (more severe ketosis), to elevate pentylenetetrazole (PTZ) seizure thresholds in adult rats and young rats. When calculating PTZ thresholds, one can use either "absolute latencies" (i.e., the number of seconds until a seizure occurs) or "threshold doses" (i.e., the milligram/kilogram dose of PTZ required to elicit a seizure). When absolute latencies were used, neither KD significantly increased the latency to seizure in adult rats and young rats. Similarly, neither KD elevated threshold doses in adult rats. The 4:1 KD did not elevate threshold doses in young rats; however, the 6.3:1 KD did. Threshold doses are sensitive to differences between group weights, and the largest difference between group weights existed between the 6.3:1 KD group and its respective control group. It remains unclear whether threshold doses, absolute latencies, or some combination of the two methods should be used when determining seizure thresholds in rats fed a KD and seizure tested by using the PTZ infusion test. We conclude that the PTZ-infusion test is not suitable for modeling the anticonvulsant effects of the KD seen clinically, especially when dietary treatments lead to significantly mismatched body weights between the groups.



     

Higher ketogenic diet ratios confer protection from seizures without neurotoxicity

The present study was designed to establish a dose-response relationship for the efficacy of the ketogenic diet (KD). Sprague-Dawley rats were fed ketogenic diets containing varying ratios of fats; (carbohydrates + proteins) whereas control animals were fed rodent chow. Unless otherwise indicated, all animals were fed calorie-restricted, isocaloric diets beginning at P37 and ketonemia, seizure threshold and neurotoxic effects were determined. Despite being provided isocaloric quantities, animals fed lower ketogenic ratios gained weight relative to those fed diets having greater proportions of fats. A significantly increased metabolic rate was noted for animals fed a high-fat diet, suggesting a basis for the weight differences. Results also showed that the animals fed calorie-restricted high-fat diets exhibited significant ketonemia and protection from pentylenetetrazole (PTZ)-induced seizures. There were no detectable neurotoxic effects for any diet group. For animals of the same age, there was no correlation between beta-hydroxybutyrate (beta-OHB) and seizure threshold. These findings suggest that beta-OHB is not directly involved in the anticonvulsant mechanism of the diet. Also, data presented here show that the conventional 4:1 ketogenic diet does not confer the greatest level of seizure protection. We conclude that a 6:1 ketogenic diet, which shows no evidence of neurotoxicity, may be maximally efficacious in rats.     

Comparison of the Anticonvulsant Efficacies and Neurotoxic Effects of Valproic Acid, Phenytoin, and the Ketogenic Diet

PURPOSE: The purpose of this study was to measure quantitatively the effectiveness of the ketogenic diet (KD) in comparison to two clinically important anticonvulsant drugs (AEDs), valproic acid (VPA) and phenytoin (PHT), and to evaluate possible associated neurotoxicity. METHODS: Rats were maintained on either a calorie-restricted, KD or calorie-restricted, rodent-chow diet for 3-5 weeks, after which neurobehavioral and seizure testing was completed. AEDs (either VPA or PHT) were injected acutely at the time to peak effect before neurotoxic and seizure assessment. Seizures were induced by timed infusion of pentylenetetrazole (PTZ) and maximal electroshock (MES). RESULTS: VPA protected from both MES- and PTZ-induced seizures, whereas the KD only elevated PTZ seizure threshold; PHT only attenuated MES-induced seizures. The KD was as effective as a high dose of VPA (i.e., 300 mg/kg) and combined treatment (i.e., KD + VPA) showed an additive increase in PTZ seizure threshold. No observed neurobehavioral deficits were associated with either diet treatment; however, drug-related side effects were noted with high doses of either VPA or PHT. CONCLUSIONS: These data suggest that the KD ranks among VPA and PHT as an effective treatment for seizures, without observed drug-associated neurobehavioral contraindications. In combination with AEDs, our results indicate that the KD plus VPA work synergistically to increase seizure threshold, whereas the KD plus PHT may be complementary, elevating seizure threshold (KD) and reducing seizure severity (PHT). These findings may provide insights into future directions for rational polytherapy; however, it is important to be aware that the KD has been shown to elevate VPA-induced hepatotoxicity.     

A comparison of the ability of a 4:1 ketogenic diet and a 6.3:1 ketogenic diet to elevate seizure thresholds in adult and young rats

PURPOSE: The pentylenetetrazol (PTZ) infusion test was used to compare seizure thresholds in adult and young rats fed either a 4:1 ketogenic diet (KD) or a 6.3:1 KD. We hypothesized that both KDs would significantly elevate seizure thresholds and that the 4:1 KD would serve as a better model of the KD used clinically. METHODS: Ninety adult rats and 75 young rats were placed on one of five experimental diets: (a) a 4:1 KD, (b) a control diet balanced to the 4:1 KD, (c) a 6.3:1 KD, (d) a standard control diet, or (e) an ad libitum standard control diet. All subjects were seizure tested by using the PTZ infusion test. Blood glucose and beta-hydroxybutyrate (beta-OHB) levels were measured. RESULTS: Neither KD elevated absolute "latencies to seizure" in young or adult rats. Similarly, neither KD elevated "threshold doses" in adult rats. In young rats, the 6.3:1 KD, but not the 4:1 KD, significantly elevated threshold doses. The 6.3:1 KD group showed poorer weight gain than the 4:1 KD group when compared with respective controls. The most dramatic discrepancies were seen in young rats. CONCLUSIONS: "Threshold doses" and "latency to seizure" data provided conflicting measures of seizure threshold. This was likely due to the inflation of threshold doses calculated by using the much smaller body weights found in the 6.3:1 KD group. Ultimately, the PTZ infusion test in rats may not be a good preparation to model the anticonvulsant effects of the KD seen clinically, especially when dietary treatments lead to significantly mismatched body weights between the groups.     

Fenofibrate, a peroxisome proliferator–activated receptor-α agonist, exerts anticonvulsive properties

The underlying mechanisms of the ketogenic diet (KD) remain unknown. Involvement of peroxisome proliferator–activated receptor-α (PPARα) has been suggested. The aim of this study was to assess the anticonvulsant properties of fenofibrate, a PPARα agonist. Wistar rats were fed at libitum during 14 days by regular diet, KD, regular diet containing 0.2% fenofibrate (F), or KD containing 0.2% fenofibrate (KD + F). Pentylenetetrazol (PTZ) threshold and latencies to the onset of status epilepticus induced by lithium–pilocarpine were used to assess diet treatments with anticonvulsive effects. Myoclonic and generalized seizure PTZ thresholds were increased in F- and KD-treated animals in comparison to control. No difference was observed between KD + F group and the others groups (control, F, KD). Latencies to the onset of status epilepticus were increased in F and KD groups compared to control. Fenofibrate exerts anticonvulsive properties comparable to KD in adult rats using PTZ and lithium–pilocarpine models. The underlying mechanisms such as PPARα activation and others should be investigated. These findings may provide insights into future directions to simplify KD protocols.     

The ketogenic diet inhibits epileptogenesis in EL mice: a genetic model for idiopathic epilepsy

PURPOSE: The ketogenic diet (KD) is a high-fat, low-carbohydrate and -protein diet that has been used to treat refractory seizures in children for more than 75 years. However, little is known about how the KD inhibits seizures or its effects on epileptogenesis. Several animal models of epilepsy have responded favorably to KD treatment, but the KD has not been studied in animals with a genetic predisposition to seizures. Here we studied the antiepileptogenic effect of the KD in EL mice, an animal model for human idiopathic epilepsy. METHODS: Young male EL mice (postnatal day 30) were randomly separated into two groups fed ad libitum with either the KD (treated, n = 21) or Agway chow (control, n = 19). The mice were weighed and tested for seizures once per week for a total of 10 weeks. The effects of the KD on plasma levels of ketone bodies and glucose were analyzed at several time points throughout the study. Associative learning was compared between treated and control animals using a water maze. RESULTS: KD treatment delayed seizure onset in young male EL mice by 1 month; however, seizure protection was transient, inasmuch as the treated and control mice experienced a similar number and intensity of seizures after 6 weeks on the diet. Plasma glucose levels and associative learning were similar in the treated and control groups, but the plasma beta-hydroxybutyrate levels were significantly higher in mice on the KD. The level of ketosis, however, was not predictive of seizure protection in EL mice. CONCLUSION: The KD delayed seizure onset in EL mice, suggesting a transient protection against epileptogenesis. The KD did not influence plasma glucose levels or associative learning. Therefore, the EL mouse may serve as a good model to study the antiepileptogenic mechanisms of the KD.     

Ketogenic Diet: Effects on Expression of Kindled Seizures and Behavior in Adult Rats

Summary: Purpose : Despite use of the ketogenic diet (KD) for >75 years its effectiveness or mechanism of action has been examined in few animal studies. Using the kindling model of epilepsy, we tested the anticonvulsant effectiveness and behavioral consequences of an experimental KD in adult rats.
Methods : Rats fully kindled from the amygdala were divided into KD-fed or standard rat diet-fed groups; diet treatment continued for 5 weeks. The KD approximated at 4:l ("classic") ketogenic diet and consisted (by weight) of 70% fat, 14% protein, no carbohydrate, and appropriate vitamins, minerals and fiber; 92% of energy provided was contributed by fat and 8% was contributed by protein. Afterdischarge threshold and duration (ADT, ADD) and stage 5 seizure threshold and duration (ST, SD) were assessed weekly for 5 weeks. During week 3, learning and memory were tested by the water maze and the behavioral response to a novel environment was assessed by the open field test.
Results : Rats receiving the KD became ketonemic and had weight gains similar to those of control rats. As compared with rats receiving a standard diet, those fed the KD had an elevated ADT and ST for the first 2 weeks of treatment. The control and KD-fed groups did not differ with regard to ADD or SD at any time during the study, and both groups performed similarly in the water maze and open field test.
Conclusions : In the kindling model, the KD afforded transient protection against the focal generation of kindled seizures but not seizure spread. Rats that received the KD did not perform differently from control-fed rats on spatial learning or exploratory behavior tasks. Our results provide a promising model for study of the anticonvulsant mechanisms of ketosis.     

Calorie-restricted ketogenic diet increases thresholds to all patterns of pentylenetetrazol-induced seizures: critical importance of electroclinical assessment

PURPOSE: Thresholds to pentylenetetrazol (PTZ) seizures were usually based only on clinical symptoms. Our purpose was to use electroclinical patterns to assess the efficacy of a ketogenic and/or calorie-restricted diet on PTZ-induced seizures. METHODS: Forty 50-day-old rats were divided in four weight-matched groups and fed controlled diets: normocalorie carbohydrate (NC), hypocalorie carbohydrate (HC), normocalorie ketogenic (NK), and hypocalorie ketogenic (HK). After 21 days, blood glucose and beta-hydroxybutyrate levels were determined and seizures were induced by continuous infusion of PTZ. The clinical and EEG thresholds to each seizure pattern were compared between the different groups. RESULTS: The electroclinical course of PTZ-induced seizures was similar in all groups. The HK group exhibited higher thresholds than the other ones for most clinical features: absence (p = 0.003), first overt myoclonia (p = 0.028), clonic seizure (p = 0.006), and for EEG features: first spike (p = 0.036), first spike-and-wave discharge (p = 0.014), subcontinuous spike-and-wave discharges (p = 0.005). NK, HC, and NC groups were not significantly different from each other. Blood glucose and beta-hydroxybutyrate levels were not correlated with electroclinical seizure thresholds. After the clonic seizure, despite stopping PTZ infusion, a tonic seizure occurred in some animals, without significant difference regarding the diet. CONCLUSION: This approach permitted a precise study of the electroclinical course of PTZ-induced seizures. In addition to the usually studied first overt myoclonia, we clearly demonstrated the efficiency of a calorie restricted KD in elevating thresholds to most electroclinical seizure patterns. We confirmed the lack of efficiency of the KD to reduce seizure severity once the seizure has started.     

Long-term effects of high lipid and high energy diet on serum lipid,brain fatty acid composition,and memory and learning ability in mice

Objective

It is well known that high lipid and high energy diet is harmful to health. But the different effects of high lipid diet composed of either saturated fatty acids or unsaturated fatty acids have not been distinguished.

Method

Eighteen pregnant C57BL/6j (22–25 g) mice were randomly divided into three groups of six each and fed with chow or high lipid diet composed of either flaxseed oil (chow diet 84%, cholesterol 0.2%, flaxseed oil 15.8%) or lard fat (chow diet 84%, cholesterol 0.2%, lard fat 15.8%). After weaning, the offspring were fed the same diet as their mothers were fed during the experiment, and their spatial memory and learning ability were evaluated by Morris water maze when they were 8 weeks old. Next, the blood and tissues were sampled when they were 9 weeks old. Serum lipids were determined using kits, and brain fatty acids were measured using a gas chromatograph.

Results

Compared to chow diet (control), high flaxseed oil diet (HFO) increased high density lipoprotein cholesterol level (HDL-C) in the mothers but not in offspring; high lard fat diet (HLF) increased serum total cholesterol level (TC) and low density lipoprotein cholesterol level (LDL-C) both in mothers and offspring. Brain fatty acids profile was altered by HLF compared with chow diet. Polyunsaturated fatty acids and long-chain polyunsaturated fatty acids content were significantly lower in the HLF group than in the control group, but saturated fatty acids content were significantly higher in HLF group than those in control group. The changed fatty acids composition affected the spatial memory and learning ability of adult offspring.

Conclusions

A long-term high lard diet increased offspring serum TC and LDL-C levels and affected the brain's fatty acid composition, and memory and learning ability. The polyunsaturated fatty acid content of the brain may be correlated with serum cholesterol levels.     

A ketogenic diet has different effects upon seizures induced by maximal electroshock and by pentylenetetrazole infusion

The purpose of these experiments was to determine whether a ketogenic diet previously shown to elevate seizure threshold also reduced seizure severity. Seizure threshold was tested by intravenous infusion of pentylenetetrazole (PTZ) whereas seizure severity was determined from measuring the hindlimb extension to flexion (E/F) ratio after seizures were evoked by maximal electroshock stimulation (MES). Surprisingly, seizures evoked by MES were more severe in animals fed a calorie-restricted ketogenic diet. Controls fed an isocaloric, calorie-restricted normal diet also exhibited more severe seizures than did animals fed the same diet ad libitum. When seizure threshold was evaluated in the same animals, those animals fed a calorie-restricted ketogenic diet exhibited a significant increase in seizure resistance compared to animals fed a ketogenic diet ad libitum, a calorie-restricted normal diet or a normal diet ad libitum. These findings suggest that both the amount and type of food affect seizures in rats and show that diet-related seizure protection depends upon the method by which seizures are provoked.     

生酮饮食对幼鼠戊四氮诱导痫性发作的影响及海马CA3区形态学观察

目的　探讨生酮饮食 (KD)对幼鼠戊四氮 (PTZ)诱导痫性发作阈值的影响及海马结构的病理改变。方法　通过尾静脉输注 PTZ,测定 KD饲料和普通饲料喂养两组 Wistar幼鼠的痫性发作阈值 ,并对其抽搐行为进行评分 ,同时对致痫后两组幼鼠海马 CA3区的病理学改变进行观察。结果　KD组幼鼠 PTZ诱导的痫性发作阈值明显高于对照组 (P <0 .0 1 ) ,但两组痫性发作的强度差异无显著性 (P >0 .0 5 )。 KD组幼鼠海马 CA3区正常锥体细胞计数较对照组明显增多 ,神经元损伤程度较轻。结论　KD可提高幼鼠 PTZ诱导的痫性发作阈值 ,但不影响发作强度 ;KD可减少痫性发作次数 ,对致痫幼鼠具有神经保护作用。     

Study of Antiepileptic Effect of Extracts from Acorus tatarinowii Schott

Summary:  Purpose: To study the antiepileptic properties of extracts from rhizomes of Acorus tatarinowii Schott (ATS).
Methods: The decoction and volatile oil were extracted from rhizomes of ATS by traditional decocting and supercritical CO₂ fluid extraction (SFE-CO₂) methods. Maximal electroshock (MES), pentylenetetrazol (PTZ) maximal seizure, and prolonged PTZ kindling models were used to test their anticonvulsive properties. The γ-aminobutyric acid (GABA) immunohistochemical reaction (IR) was used to study GABAergic neuron changes in the PTZ kindling model and the effects of treatment.
Results: Both decoction (dose; 10–20 g/kg) and volatile oil (1.25 g/kg) of ATS decreased the convulsive rate significantly in the MES model. Decoction of ATS was shown to be effective in the PTZ model with both decreased convulsive and mortality rates. The volatile oil of ATS failed to prevent seizures in the dose range tested, although prolonged seizure latency and decreased mortality were found at a dose of 1.25 g/kg. In the PTZ kindling model, GABA-IR neurons decreased obviously compared with the normal group. In the groups treated with the decoction and volatile oil, the seizure intensity decreased significantly after treatment. Increased GABA-IR neurons also were found when compared with PTZ kindling controls. Morphologic observation also showed that GABA-IR neuron damage was less severe in the drug-treated groups.
Conclusions: Both decoction and volatile oil extracted from the rhizome of Acorus tatarinowii Schott have anticonvulsive effects. The volatile oil is shown to be less effective for PTZ-induced convulsions. Both extracts can prevent convulsions as well as convulsion-related GABAergic neuron damage in the brain in the prolonged PTZ kindling model.     

Does the ketogenic ratio matter when using ketogenic diet therapy in pediatric epilepsy?

The ketogenic diet (KD) is a widely used therapeutic option for individuals with medically refractory epilepsy. As the diet's name implies, ketosis is a historically important component of the diet, but it is not well understood how important ketosis is for seizure control. The ketogenic ratio is defined as the ratio of fat to carbohydrate plus protein by weight in the diet (grams). Traditionally, the classic KD contains a 4:1 ratio, and a very high proportion of fat in the diet. The classic KD, with its high proportion of fat and limited carbohydrate intake can be restrictive for patients with epilepsy. Recently, there is experience with use of lower ketogenic ratios and less-restrictive diets such as the modified Atkins diet and the low glycemic index treatment. In this narrative review, we examine the role of ketosis and ketogenic ratios in determining the efficacy of the KD in children with epilepsy.     

Hydroalcoholic extract of Zizyphus jujuba ameliorates seizures, oxidative stress, and cognitive impairment in experimental models of epilepsy in rats

The anticonvulsant effect of the hydroalcoholic extract of Zizyphus jujuba (HEZJ) fruit (100, 250, 500, and 1000 mg/kg, orally) was evaluated in experimental seizure models in rats. The effect of HEZJ on seizure-induced cognitive impairment, oxidative stress, and cholinesterase activity was also investigated. HEZJ (1000 mg/kg) exhibited maximum protection (100%) against generalized tonic-clonic seizures in the pentylenetetrazole (PTZ) seizure model and and 66.7% protection against tonic hindlimb extension in the maximal electroshock (MES) seizure model. Significant impairment in cognitive functions was observed in both PTZ- and MES-challenged rats. Pretreatment with HEZJ resulted in significant improvement in learning and memory. HEZJ also reversed the oxidative stress induced by both PTZ and MES. The significant decrease in cholinesterase activity observed in the PTZ and MES models was significantly reversed by pretreatment with HEZJ. Thus, the present study demonstrates the anticonvulsant effect of HEZJ as well as amelioration of cognitive impairment induced by seizures in rats.     

A Ketogenic Diet Increases the Resistance to Pentylenetetrazole-Induced Seizures in the Rat

Summary: Purpose: The purpose of this study was to test the hypothesis that a ketogenic diet would increase the resistance of rats to pentylenetetrazole (PTZ)-induced seizures and to understand the relation of ketonemia to seizure resistance.
Methods: A freely consumed, high-fat (ketogenic) diet was administered to male Sprague-Dawley rats for 5–10 weeks, while control animals were fed either rodent chow or a high-carbohydrate diet. Ketonemia was measured as plasma levels of β-hydroxybutyric acid (β-OHB). Seizures were induced by tail-vein infusion of pentylenetetrazole.
Results: The ketogenic diet produced a highly significant (p <0.01) increase in β-OHB levels within 5 days. Induction of seizures by PTZ 35 days after animals were placed on their respective diets showed that ketogenic animals had a significantly (p <0.01) increased threshold for seizure induction compared with those fed an isocaloric diet of either high-carbohydrate or normal rodent chow. Ketogenic animals did not exhibit increased seizure severity relative to controls, despite receiving consistently higher doses of PTZ.
Conclusions: The ketogenic diet resulted in an increased seizure threshold, confirming the hypothesis, and seizure threshold was found to be a direct function of the level of ketonemia.     

A modified Atkins diet is effective for the treatment of intractable pediatric epilepsy

PURPOSE: The Atkins diet may induce ketosis as does the ketogenic diet, without restrictions on calories, fluids, protein, or need for an inpatient fast and admission. Our objective was to evaluate the efficacy and tolerability of a modified Atkins diet for intractable childhood epilepsy. METHODS: Twenty children were treated prospectively in a hospital-based ambulatory clinic from September 2003 to May 2005. Children aged 3-18 years, with at least three seizures per week, who had been treated with at least two anticonvulsants, were enrolled and received the diet over a 6-month period. Carbohydrates were initially limited to 10 g/day, and fats were encouraged. Parents measured urinary ketones semiweekly and recorded seizures daily. All children received vitamin and calcium supplementation. RESULTS: In all children, at least moderate urinary ketosis developed within 4 days (mean, 1.9). Sixteen (80%) completed the 6-month study; 14 chose to remain on the diet afterward. At 6 months, 13 (65%) had >50% improvement, and seven (35%) had >90% improvement (four were seizure free). Mean seizure frequency after 6 months was 40 per week (p = 0.005). Over a 6-month period, mean serum blood urea nitrogen increased from 12 to 17 mg/dl (p = 0.01); creatinine was unchanged. Cholesterol increased from 192 to 221 mg/dl, (p = 0.06). Weight did not change significantly (34.0-33.7 kg); only six children lost weight. A stable body mass index over time correlated with >90% improvement (p = 0.004). CONCLUSIONS: A modified Atkins diet is an effective and well-tolerated therapy for intractable pediatric epilepsy.     

The ketogenic diet for super-refractory status epilepticus patients in intensive care units

Objectives

Super-refractory status epilepticus (SRSE) is one of the most challenging issues in intensive care units (ICUs) in that it is associated with high morbidity and mortality. Although the ketogenic diet (KD) has been reported to be effective in treating of SRSE, the use of the diet as therapy can be complicated by concomitant medical problems specific to critically ill patients. In this study, we aimed to describe our experience of the KD for SRSE patients in ICUs.

Growth dependence on insulin-like growth factor-1 during the ketogenic diet

Purpose:   To examine the influence of the ketogenic diet (KD) on linear growth and insulin-like growth factor I (IGF-I) levels in children with pharmacotherapy-resistant epilepsy.
Methods:   A prospective study was designed to evaluate growth, serum IGF-I levels, blood β-hydroxybutyric acid (β-OHB), and seizure frequency before and during KD in 22 children (median age 5.5 years). Growth was assessed by measurements of weight, height, body mass index (BMI), and height velocity. Standard deviation scores (SDS) were calculated for all measured parameters as well as for serum IGF-I to eliminate the influence of age- and sex-related differences among patients.
Results:   Fourteen of the 22 patients responded to the KD. Weight, height, BMI, and height velocity decreased significantly during the KD. We found that the KD had profound influence on growth and IGF-I levels. No correlation was found between seizure response and growth alterations. Height velocity correlated negatively with β-OHB during the KD. The slope of the regression of height velocity against IGF-I decreased significantly during the KD.
Conclusions:   Height velocity was most affected in those with pronounced ketosis, which implies that, in clinical practice, the level of ketosis should be related to outcomes in seizure response and growth. Our data indicate that growth disturbances and the decreased sensitivity of growth to similar IGF-I levels during KD are independent of seizure reduction. The metabolic status induced by KD may be the mechanism underlying both alterations of linear growth and seizure reduction.     

The ketogenic diet as a treatment option in adults with chronic refractory epilepsy: efficacy and tolerability in clinical practice

The ketogenic diet (KD) is a high-fat, low-protein, low-carbohydrate diet that is used as a treatment for patients with difficult-to-control epilepsy. The present study assesses the efficacy and tolerability of the KD as an add-on therapy in adults with chronic refractory epilepsy. 15 adults were treated with the classical diet or MCT diet. During a follow-up period of 1 year we assessed seizure frequency, seizure severity, tolerability, cognitive performance, mood and quality of life (QOL). We found a significant reduction in seizures among the patients who followed the diet at least 1 year (n=5). Of these 5 patients, 2 had a reduction between 50 and 90%. Analyzing the study months separately, we found a seizure reduction of ≥50% in 26.6% of the patients during at least 1 month of treatment. Common side-effects were gastrointestinal disorders, loss of weight and fatigue. There was a considerable, non-significant improvement found in mood and QOL scores. Improvements were independent of reduction in seizure frequency, indicating that the effects of the KD reach further than seizure control.     

Timed pentylenetetrazol infusion test: a comparative analysis with s.c.PTZ and MES models of anticonvulsant screening in mice.

The intravenous pentylenetetrazol (i.v.PTZ) seizure test provides threshold dose for induction of seizures in individual animals. In the present study, the i.v. and s.c.PTZ seizure models in mice were compared for seizure pattern, intra- and interanimal variability. Anticonvulsant activities of several antiepileptic drugs (AEDs) at non-ataxic dose levels were evaluated in the PTZ and maximal electroshock (MES) seizure tests. In the i.v.PTZ test, at 0.5 ml/min rate of administration, the mean threshold PTZ doses for induction of clonus and tonic extensor were 44.17 and 99.59 mg/kg, respectively. The intra- and interanimal variabilities in the seizure response were low in the i.v.PTZ as compared to the s.c.PTZ model. Phenobarbital sodium, ethosuximide, sodium valproate, diazepam, tiagabine, oxcarbazepine and zonisamide enhanced threshold or onset latency for clonus in the i.v. and s.c.PTZ tests, respectively. Levetiracetam and pregabalin were active in the i.v.PTZ test, but had no effect in the s.c.PTZ test. Ability of AEDs to protect from tonic extensor was compared in the MES and i.v.PTZ tests. For this effect, phenobarbital sodium, phenytoin, carbamazepine, sodium valproate, gabapentin, oxcarbazepine, zonisamide and pregabalin were effective in the i.v.PTZ and MES tests. Ethosuximide, diazepam and levetiracetam were effective in the i.v.PTZ test, but not the MES test. On the contrary, lamotrigine and topiramate were active in the MES, but not the i.v.PTZ test. These results indicate that it is advantageous to use i.v.PTZ test as an acute seizure model for screening of antiepileptic drugs. This model can identify molecules with varied mechanism of action and broad clinical utility in the treatment of epilepsy.