Topiramate rapidly raises brain GABA in epilepsy patients

Mechanisms of neurodevelopmental toxicity of topiramate

Prescriptions for antiseizure medications (ASMs) have been rapidly growing over the last several decades due, in part, to an expanding list of clinical indications for which they are now prescribed. This trend has raised concern for potential adverse neurodevelopmental outcomes in ASM-exposed pregnancies. Recent large scale population studies have suggested that the use of topiramate (TOPAMAX, Janssen-Cilag), when prescribed for seizure control, migraines, and/or weight management, is associated with an increased risk for autism spectrum disorder (ASD), intellectual disability, and attention-deficit/hyperactivity disorder (ADHD) in exposed offspring. Here, we critically review epidemiologic evidence demonstrating the neurobehavioral teratogenicity of topiramate and speculate on the neuromolecular mechanisms by which prenatal exposure may perturb neurocognitive development. Specifically, we explore the potential role of topiramate's pharmacological interactions with ligand- and voltage-gated ion channels, especially GABAergic signaling, its effects on DNA methylation and histone acetylation, whether topiramate induces oxidative stress, and its association with fetal growth restriction as possible mechanisms contributing to neurodevelopmental toxicity. Resolving this biology will be necessary to reduce the risk of adverse pregnancy outcomes caused by topiramate or other ASMs.

Topiramate alters the gut microbiome to aid in its anti-seizure effect

Introduction

There is a growing interest in the role of the gut microbiota in epilepsy, however, it is unclear if anti-seizure medications (ASMs) play a role in the gut-brain axis. To test this, we investigated the impact of the ASM topiramate on the gut microbiome of mice.

Methods

C57BL/6J mice were administered topiramate in their drinking water for 5 weeks. 16S ribosomal RNA gene sequencing was performed on fecal samples collected at 5 weeks. Analysis of alpha diversity, beta diversity, and differential abundance were performed. Cecal contents were analyzed for short-chain fatty acids (SCFAs) composition. Pentylenetetrazol (PTZ)-kindling was performed in saline, topiramate, Lactobacillus johnsonii, and topiramate and Lactobacillus johnsonii treated mice. Mice received PTZ injection every other day for a total of twelve injections, seizure activity was video monitored for 30 minutes and scored.

Results and discussion

Our study revealed that topiramate ingestion significantly increased Lactobacillus johnsonii in the gut microbiome of naïve mice. Treatment with topiramate and Lactobacillus johnsonii together, but not alone, reduced susceptibility to PTZ-induced seizures. Co-treatment also significantly increased the percent of butyrate and the abundance of butyrate-producing family Lachnospiraceae in the gut, and elevated the GABA/glutamate ratio in the cortex. Our results demonstrate that an ASM can alter the gut microbiome to aid in their anti-seizure effect in vivo and suggest the potential of the probiotic Lactobacillus johnsonii as an adjunct therapy with topiramate in reducing seizure susceptibility.

In vivo laser speckle contrast imaging of 4-aminopyridine- or pentylenetetrazole-induced seizures

Clinical and preclinical studies on epileptic seizures are closely linked to the study of neurovascular coupling. Obtaining reliable information about cerebral blood flow (CBF) in the area of epileptic activity through minimally invasive techniques is crucial for research in this field. In our studies, we used laser speckle contrast imaging (LSCI) to gather information about the local blood circulation in the area of epileptic activity. We used two models of epileptic seizures: one based on 4-aminopyridine (4-AP) and another based on pentylenetetrazole (PTZ). We verified the duration of an epileptic seizure using electrocorticography (ECoG). We applied the antiepileptic drug topiramate (TPM) to both models, but its effect was different in each case. However, in both models, TPM had an effect on neurovascular coupling in the area of epileptic activity, as shown by both LSCI and ECoG data. We demonstrated that TPM significantly reduced the amplitude of 4-AP-induced epileptic seizures (4-AP+TPM: 0.61 ± 0.13 mV vs 4-AP: 1.08 ± 0.19 mV; p < 0.05), and it also reduced gamma power in ECoG in PTZ-induced epileptic seizures (PTZ+TPM: 38.5% ± 11.9% of the peak value vs PTZ: 59.2% ± 3.0% of peak value; p < 0.05). We also captured the pattern of CBF changes during focal epileptic seizures induced by 4-AP. Our data confirm that the system of simultaneous cortical LSCI and registration of ECoG makes it possible to evaluate the effectiveness of pharmacological agents in various types of epileptic seizures in in vivo models and provides spatial and temporal information on the process of ictogenesis.

J-difference GABA-edited MRS reveals altered cerebello-thalamo-cortical metabolism in patients with hepatic encephalopathy

Hepatic encephalopathy (HE) is a common neurological manifestation of liver cirrhosis and is characterized by an increase of ammonia in the brain accompanied by a disrupted neurotransmitter balance, including the GABAergic and glutamatergic systems. The aim of this study is to investigate metabolic abnormalities in the cerebello-thalamo-cortical system of HE patients using GABA-edited MRS and links between metabolite levels, disease severity, critical flicker frequency (CFF), motor performance scores, and blood ammonia levels. GABA-edited MRS was performed in 35 participants (16 controls, 19 HE patients) on a clinical 3 T MRI system. MRS voxels were placed in the right cerebellum, left thalamus, and left motor cortex. Levels of GABA+ and of other metabolites of interest (glutamine, glutamate, myo-inositol, glutathione, total choline, total NAA, and total creatine) were assessed. Group differences in metabolite levels and associations with clinical metrics were tested. GABA+ levels were significantly increased in the cerebellum of patients with HE. GABA+ levels in the motor cortex were significantly decreased in HE patients, and correlated with the CFF (r = 0.73; p < .05) and motor performance scores (r = -0.65; p < .05). Well-established HE-typical metabolite patterns (increased glutamine, decreased myo-inositol and total choline) were confirmed in all three regions and were closely linked to clinical metrics. In summary, our findings provide further evidence for alterations in the GABAergic system in the cerebellum and motor cortex in HE. These changes were accompanied by characteristic patterns of osmolytes and oxidative stress markers in the cerebello-thalamo-cortical system. These metabolic disturbances are a likely contributor to HE motor symptoms in HE. In patients with hepatic encephalopathy, GABA+ levels in the cerebello-thalamo-cortical loop are significantly increased in the cerebellum and significantly decreased in the motor cortex. GABA+ levels in the motor cortex strongly correlate with critical flicker frequency (CFF) and motor performance score (pegboard test tPEG), but not blood ammonia levels (NH3).

Comparison of linear combination modeling strategies for edited magnetic resonance spectroscopy at 3 T

J-difference-edited spectroscopy is a valuable approach for the in vivo detection of γ-aminobutyric-acid (GABA) with magnetic resonance spectroscopy (MRS). A recent expert consensus article recommends linear combination modeling (LCM) of edited MRS but does not give specific details regarding implementation. This study explores different modeling strategies to adapt LCM for GABA-edited MRS. Sixty-one medial parietal lobe GABA-edited MEGA-PRESS spectra from a recent 3-T multisite study were modeled using 102 different strategies combining six different approaches to account for co-edited macromolecules (MMs), three modeling ranges, three baseline knot spacings, and the use of basis sets with or without homocarnosine. The resulting GABA and GABA+ estimates (quantified relative to total creatine), the residuals at different ranges, standard deviations and coefficients of variation (CVs), and Akaike information criteria, were used to evaluate the models' performance. Significantly different GABA+ and GABA estimates were found when a well-parameterized MM_3co basis function was included in the model. The mean GABA estimates were significantly lower when modeling MM_3co , while the CVs were similar. A sparser spline knot spacing led to lower variation in the GABA and GABA+ estimates, and a narrower modeling range-only including the signals of interest-did not substantially improve or degrade modeling performance. Additionally, the results suggest that LCM can separate GABA and the underlying co-edited MM_3co . Incorporating homocarnosine into the modeling did not significantly improve variance in GABA+ estimates. In conclusion, GABA-edited MRS is most appropriately quantified by LCM with a well-parameterized co-edited MM_3co basis function with a constraint to the nonoverlapped MM_0.93 , in combination with a sparse spline knot spacing (0.55 ppm) and a modeling range of 0.5-4 ppm.

Carbonic Anhydrase Inhibitors and Epilepsy: State of the Art and Future Perspectives

Carbonic anhydrases (CAs) are a group of ubiquitously expressed metalloenzymes that catalyze the reversible hydration/dehydration of CO₂/HCO₃. Thus, they are involved in those physiological and pathological processes in which cellular pH buffering plays a relevant role. The inhibition of CAs has pharmacologic applications for several diseases. In addition to the well-known employment of CA inhibitors (CAIs) as diuretics and antiglaucoma drugs, it has recently been demonstrated that CAIs could be considered as valid therapeutic agents against obesity, cancer, kidney dysfunction, migraine, Alzheimer's disease and epilepsy. Epilepsy is a chronic brain disorder that dramatically affects people of all ages. It is characterized by spontaneous recurrent seizures that are related to a rapid change in ionic composition, including an increase in intracellular potassium concentration and pH shifts. It has been reported that CAs II, VII and XIV are implicated in epilepsy. In this context, selective CAIs towards the mentioned isoforms (CAs II, VII and XIV) have been proposed and actually exploited as anticonvulsants agents in the treatment of epilepsy. Here, we describe the research achievements published on CAIs, focusing on those clinically used as anticonvulsants. In particular, we examine the new CAIs currently under development that might represent novel therapeutic options for the treatment of epilepsy.

Effective treatments for FGF12-related early-onset epileptic encephalopathies patients

BACKGROUND

FGF12 (FHF1) gene encodes voltage-gated sodium channel (Nav)-binding protein fibroblast growth factor homologous factor 1, which could cause seizures by regulating voltage dependence of Nav fast inactivation and neuron excitability. The most common pathogenic variant FGF12 c.341G > A related early-onset epileptic encephalopathies (EOEE) was characterized by intractable seizures and developmental disabilities.

RESULTS

Using whole exome sequencing, a de novo hotspot variant c.341G > A (NM_021032.4) of FGF12 was identified in three unrelated EOEE probands. All probands were seizure free after a combination treatment of valproic acid (VPA) and topiramate (TPM). The motor and cognitive skills in two probands were improved due to the early and effective treatment. In order to compare the effectiveness of different treatment strategies for the disease, a review of treatments for FGF12-related epilepsy was made.

CONCLUSION

We reported three FGF12 c.341G > A related EOEE patients responded well to a combination antiepileptic therapy of VPA and TPM. The current study is the first to describe the combination therapy of VPA and TPM in FGF12 c.341G > A related EOEE patients. This study may contribute to future medication consultation for intractable epilepsy with FGF12 hotspot variants.

Anticonvulsant Effects of Carbonic Anhydrase Inhibitors: The Enigmatic Link Between Carbonic Anhydrases and Electrical Activity of the Brain

Acetazolamide (ACZ), a sulfonamide carbonic anhydrase (CA) inhibitor, was first introduced into medical use as a diuretic in the1950s. Shortly after its introduction, its antiglaucoma and anticonvulsant properties came to light. Subsequently, studies of ACZ have explored a plethora of neurophysiological functions of CAs in the CNS. In addition, topiramate (TPM) and zonisamide (ZNS), which were developed as antiepileptic drugs (AEDs) in the1990s, were found to have the ability to inhibit CAs. How CA inhibition prevents seizures is elusive. CA expression and activity are extensively detected in neurons, the choroid plexus, oligodendrocytes and astrocytes. TPM and ZNS appear to produce multimodal actions in the CNS as well as CA inhibition unlike ACZ. Nonetheless, CA inhibitors share some common denominators. They do not only affect the fine equilibrium among CO₂, H⁺ and HCO₃^- in the extraneuronal and intraneuronal milieu, but also modulate the activity of ligand gated ion channels at the neuronal level such as GABA-A signaling through inhibiting CA-replenished HCO₃^- efflux. In addition, there are studies reporting their ability to alter Ca²⁺ kinetics through modulation of ligand gated Ca²⁺ channels, voltage gated Ca²⁺ channels (VGCC) or Ca²⁺-induced Ca²⁺ release channels (CICRC). The present study will review the involvement of CAs in the formation of epileptogenesis, and likely mechanisms by which CA inhibitors suppress the electrical activity of the brain. The common properties of CA inhibitors provide some clues for a possible link among metabolism, CAs, Ca²⁺ and GABA signaling.

Tracking the motion of the KV1.2 voltage sensor reveals the molecular perturbations caused by a de novo mutation in a case of epilepsy

KEY POINTS

KV1.2 channels, encoded by the KCNA2 gene, regulate neuronal excitability by conducting K+ upon depolarization. A new KCNA2 missense variant was discovered in a patient with epilepsy, causing amino acid substitution F302L at helix S4, in the KV1.2 voltage-sensing domain. Immunocytochemistry and flow cytometry showed that F302L does not impair KCNA2 subunit surface trafficking. Molecular dynamics simulations indicated that F302L alters the exposure of S4 residues to membrane lipids. Voltage clamp fluorometry revealed that the voltage-sensing domain of KV1.2-F302L channels is more sensitive to depolarization. Accordingly, KV1.2-F302L channels opened faster and at more negative potentials; however, they also exhibited enhanced inactivation: that is, F302L causes both gain- and loss-of-function effects. Coexpression of KCNA2-WT and -F302L did not fully rescue these effects. The proband's symptoms are more characteristic of patients with loss of KCNA2 function. Enhanced KV1.2 inactivation could lead to increased synaptic release in excitatory neurons, steering neuronal circuits towards epilepsy.

ABSTRACT

An exome-based diagnostic panel in an infant with epilepsy revealed a previously unreported de novo missense variant in KCNA2, which encodes voltage-gated K+ channel KV1.2. This variant causes substitution F302L, in helix S4 of the KV1.2 voltage-sensing domain (VSD). F302L does not affect KCNA2 subunit membrane trafficking. However, it does alter channel functional properties, accelerating channel opening at more hyperpolarized membrane potentials, indicating gain of function. F302L also caused loss of KV1.2 function via accelerated inactivation onset, decelerated recovery and shifted inactivation voltage dependence to more negative potentials. These effects, which are not fully rescued by coexpression of wild-type and mutant KCNA2 subunits, probably result from the enhancement of VSD function, as demonstrated by optically tracking VSD depolarization-evoked conformational rearrangements. In turn, molecular dynamics simulations suggest altered VSD exposure to membrane lipids. Compared to other encephalopathy patients with KCNA2 mutations, the proband exhibits mild neurological impairment, more characteristic of patients with KCNA2 loss of function. Based on this information, we propose a mechanism of epileptogenesis based on enhanced KV1.2 inactivation leading to increased synaptic release preferentially in excitatory neurons, and hence the perturbation of the excitatory/inhibitory balance of neuronal circuits.

Peptide based therapeutics and their use for the treatment of neurodegenerative and other diseases

Bioactive peptides are actively involved in different biological functions and importantly contribute to human health, and the use of peptides as therapeutics has a long successful history in disease management. A number of peptides have wide-ranging therapeutic effects, such as antioxidant, antimicrobial, and antithrombotic effects. Neurodegenerative diseases are typically caused by abnormal aggregations of proteins or peptides, and the depositions of these aggregates in or on neurons, disrupt signaling and eventually kill neurons. During recent years, research on short peptides has advanced tremendously. This review offers a brief introduction to peptide based therapeutics and their application in disease management and provides an overview of peptide vaccines, and toxicity related issues. In addition, the importance of peptides in the management of different neurodegenerative diseases and their therapeutic applications is discussed. The present review provides an understanding of peptides and their applications for the management of different diseases, but with focus on neurodegenerative diseases. The role of peptides as anti-cancer, antimicrobial and antidiabetic agents has also been discussed.

Applications of Yoga in Psychiatry: What We Know

Yoga has been in use for thousands of years in the East as a healing modality. Western practitioners are now starting to recognize the potential of yoga-based treatments. The purpose of this article is to explore the evidence-base of yoga-based treatments for depression and anxiety with the purpose of furthering the integration of yoga into conventional Western mental health treatment plans.

Topiramate in Migraine Prevention: A 2016 Perspective

BACKGROUND

In evidence-based guidelines published in 2000, topiramate was a third-tier migraine preventive with no scientific evidence of efficacy; recommendation for its use reflected consensus opinion and clinical experience. Its neurostabilizing activity, coupled with its favorable weight profile, made topiramate an attractive alternative to other migraine preventives that caused weight gain. When guidelines for migraine prevention in episodic migraine were published in 2012, topiramate was included as a first-line option based on double-blind, randomized controlled trials involving nearly 3000 patients. The scientific and clinical interest in topiramate has generated a large body of data from randomized controlled trials, meta-analyses, patient registries, cohort studies, and claims data analyses that have more fully characterized its role as a migraine preventive.

AIM

This article will review the profile of topiramate that has emerged out of the past decade of research and clinical use in migraine prophylaxis. It will also address the rationale for extended-release (XR) formulations in optimizing topiramate therapy in migraine.

SUMMARY

Topiramate has activity at multiple molecular targets, which may account for why it is effective in migraine and most other, more specific, anticonvulsants are not. Based on randomized controlled trials, topiramate reduces migraine frequency and acute medication use, improves quality of life, and reduces disability in patients with episodic migraine and in those with chronic migraine with or without medication overuse headache. Its efficacy in chronic migraine is not improved by the addition of propranolol. Topiramate's ability to prevent progression from high-frequency episodic migraine to chronic migraine remains unclear. Consistent with clinicians' perceptions, migraineurs are more sensitive to topiramate-associated side effects than patients with epilepsy. Paresthesia is a common occurrence early in treatment but is rarely cause for terminating topiramate treatment. Cognitive problems occur much less frequently than paresthesia but are more troublesome in terms of treatment discontinuation. Cognitive complaints can often be managed by slowly increasing the topiramate dose in small increments to allow habituation. As with other carbonic anhydrase inhibitors, topiramate has metabolic effects that favor the development of metabolic acidosis and possibly renal stones. Because migraineurs have an increased risk of renal stones independent of topiramate exposure, clinicians should counsel all migraine patients to maintain hydration. Abrupt onset of blurring, other visual disturbances, and/or ocular pain following topiramate's initiation should be evaluated promptly since this may indicate rare but potentially sight-threatening idiosyncratic events. Postmarketing evidence has shown that first-trimester exposure to topiramate monotherapy is associated with increased occurrence of cleft lip with or without cleft palate (Pregnancy Category D). Even though topiramate's long half-life would seemingly support q.d. dosing, randomized controlled migraine trials used b.i.d. administration of immediate-release (IR) topiramate, which has more favorable plasma concentration-time profile (ie, lower peak concentrations and higher trough concentrations) than q.d. IR dosing. Given the sensitivity of migraineurs to topiramate-related adverse events, particularly cognitive effects, pharmacokinetic profiles should be considered when optimizing migraine outcomes. The extended-release (XR) formulations Qudexy^® XR (Upsher-Smith Laboratories) and Trokendi XR^® (Supernus Pharmaceuticals) were specifically designed to achieve the adherence benefits of q.d. dosing but with more favorable (ie, more constant) steady-state plasma concentrations over the 24-hour dosing interval vs IR topiramate b.i.d. Intriguing results from a study in healthy volunteers showed consistently less impairment in neuropsychometric tests of verbal fluency and mental processing speed with an XR topiramate formulation (Trokendi XR) vs IR topiramate b.i.d. These findings suggest a pharmacodynamic effect associated with significantly reducing plasma concentration fluctuation when topiramate absorption is slowed. Results of retrospective studies in migraineurs treated with XR topiramate appear to support a clinically meaningful benefit of XR topiramate vs IR topiramate in terms of significantly fewer cognitive effects, improved adherence, and overall better outcomes of migraine prophylaxis with topiramate.

Metabolic and functional MR biomarkers of antiepileptic drug effectiveness: A review

As a large number of patients with epilepsy do not respond favorably to antiepileptic drugs (AEDs), a better understanding of treatment failure and the cause of adverse side effects is required. The working mechanisms of AEDs also alter neurotransmitter concentrations and brain activity, which can be measured using MR spectroscopy and functional MR imaging, respectively. This review presents an overview of clinical research of MR spectroscopy and functional MR imaging studies to the effects of AEDs on the brain. Despite the scarcity of studies associating MR findings to the effectiveness of AEDs, the current research shows clear potential regarding this matter. Several GABAergic AEDs have been shown to increase the GABA concentration, which was related to seizure reductions, while language problems due to topiramate have been associated with altered activation patterns measured with functional MR imaging. MR spectroscopy and functional MR imaging provide biomarkers that may predict individual treatment outcomes, and enable the assessment of mechanisms of treatment failure and cognitive side effects.

Enteral topiramate in a pediatric patient with refractory status epilepticus: a case report and review of the literature

We describe the use of topiramate in a healthy 12-year-old (88-kg) male who developed refractory generalized convulsive status epilepticus. Seizures persisted despite aggressive use of benzodiazepines (intravenous lorazepam; oral clorazepate), barbiturates (i.e., phenobarbital, pentobarbital), and hydantoins. The child's seizures were controlled with nasogastrically administered topiramate in doses up to 500 mg twice daily (11.4 mg/kg/day). The patient did not display any clinical or laboratory signs of metabolic acidosis while receiving topiramate. Topiramate should be considered as a treatment option in refractory status epilepticus.

An update of the classical and novel methods used for measuring fast neurotransmitters during normal and brain altered function

To understand better the cerebral functions, several methods have been developed to study the brain activity, they could be related with morphological, electrophysiological, molecular and neurochemical techniques. Monitoring neurotransmitter concentration is a key role to know better how the brain works during normal or pathological conditions, as well as for studying the changes in neurotransmitter concentration with the use of several drugs that could affect or reestablish the normal brain activity. Immediate response of the brain to environmental conditions is related with the release of the fast acting neurotransmission by glutamate (Glu), γ-aminobutyric acid (GABA) and acetylcholine (ACh) through the opening of ligand-operated ion channels. Neurotransmitter release is mainly determined by the classical microdialysis technique, this is generally coupled to high performance liquid chromatography (HPLC). Detection of neurotransmitters can be done by fluorescence, optical density, electrochemistry or other detection systems more sophisticated. Although the microdialysis method is the golden technique to monitor the brain neurotransmitters, it has a poor temporal resolution. Recently, with the use of biosensor the drawback of temporal resolution has been improved considerably, however other inconveniences have merged, such as stability, reproducibility and the lack of reliable biosensors mainly for GABA. The aim of this review is to show the important advances in the different ways to measure neurotransmitter concentrations; both with the use of classic techniques as well as with the novel methods and alternant approaches to improve the temporal resolution.

Second generation anti-epileptic drugs adversely affect reproductive functions in young non-epileptic female rats

Reproductive endocrine disturbances are a major health concern in women with epilepsy due to their long term use of antiepileptic drugs (AEDs). Second generation AEDs such as topiramate (TPM) and gabapentin are frequently used for the treatment of epilepsy as well as migraine, bipolar disorder etc. Despite the widespread clinical complications, however the definitive mechanism(s) mediating the side effects of TPM and gabapentin remain obscure. The present study was aimed to evaluate the long term effects of TPM and gabapentin on reproductive functions in young female Wistar rats. Estrous cyclicity, ovarian histology as well as estradiol, LH, leptin and insulin hormones level were studied to elucidate the long-term effect of these AEDs monotherapy on reproductive functions in non-epileptic animals. Further to explore the effects on gonadotropin releasing hormone (GnRH) neuroendocrine plasticity, the expression of GnRH, gamma-amino butyric acid (GABA), glutamic acid decarboxylase (GAD), glial fibrilliary acidic protein (GFAP) and polysialylated form of neural cell adhesion molecule (PSA-NCAM) was studied in median eminence (ME) region of these animals by immunohistochemistry, Western blot hybridization and RT-PCR. Our results demonstrate that TPM and gabapentin treatment for 8 weeks cause reproductive dysfunction as ascertained by disturbed hormonal levels and estrous cyclicity as well as alterations in GABAergic system and GnRH neuronal-glial plasticity. Our findings suggest that treatment with TPM and gabapentin disrupts the complete hypothalamo-hypophyseal-gonadal axis (HPG) through GnRH pulse generator in hypothalamus.

Antiepileptic drug therapy and monitoring

Over the past 2 decades, the number of antiepileptic drugs (AEDs) available to veterinarians has grown exponentially. Coupled with this increase is the ability to rapidly and accurately diagnose underlying brain disease with readily accessible magnetic resonance imaging. As a result, the veterinary community is attuned to the need for early treatment intervention. As more treatment choices become available, the unrelenting questions still arise are when should treatment begin, which initial drug therapy is best for our patients, when should treatment changes be considered, and finally, what are the advantages that newer drugs provide for our patients. The purpose of this chapter is to review decision-making strategies for AED therapy, provide an overview of the applicability of current AED available, and present information on the therapeutic advances in epilepsy.

GABAergic contributions to alcohol responsivity during adolescence: insights from preclinical and clinical studies

There is a considerable body of literature demonstrating that adolescence is a unique age period, which includes rapid and dramatic maturation of behavioral, cognitive, hormonal and neurobiological systems. Most notably, adolescence is also a period of unique responsiveness to alcohol effects, with both hyposensitivity and hypersensitivity observed to the various effects of alcohol. Multiple neurotransmitter systems are undergoing fine-tuning during this critical period of brain development, including those that contribute to the rewarding effects of drugs of abuse. The role of developmental maturation of the γ-amino-butyric acid (GABA) system, however, has received less attention in contributing to age-specific alcohol sensitivities. This review integrates GABA findings from human magnetic resonance spectroscopy studies as they may translate to understanding adolescent-specific responsiveness to alcohol effects. Better understanding of the vulnerability of the GABA system both during adolescent development, and in psychiatric conditions that include alcohol dependence, could point to a putative mechanism, boosting brain GABA, that may have increased effectiveness for treating alcohol use disorders.

Topiramate's effects on cocaine-induced subjective mood, craving and preference for money over drug taking

Topiramate, presumably through antagonism of excitatory glutaminergic pathways and facilitation of inhibitory gamma-aminobutyric acid neurons in the cortico-mesolimbic system, might reduce cocaine's abuse liability. We tested whether topiramate (100 mg twice daily) would reduce the euphoria, subjective mood, craving and preference for cocaine over money induced by low and high doses (0.325 and 0.65 mg/kg i.v., respectively) of experimentally administered cocaine in 24 male and female, cocaine-dependent, non-treatment-seeking research volunteers in a university in-patient laboratory. We utilized a randomized, double-blind, placebo-controlled, within-subject, Latin-square cross-over design in which three experimental challenge doses of low-dose cocaine, high-dose cocaine and placebo were administered in counterbalanced order after 5 days of topiramate or matching placebo pre-treatments separated by a 1-week washout period (2006-2009). After placebo pre-treatments, cocaine produced dose-related increases in euphoria, stimulant effects, craving for more cocaine and monetary value of cocaine in a behavioral preference test of cocaine versus money choice. Topiramate pre-treatment reduced the cocaine-related craving and monetary value of high-dose cocaine while increasing the monetary value, euphoria and stimulant effects of low-dose cocaine. Validated and standardized human experimental methods evaluating the potential for topiramate to alter cocaine's abuse liability suggest that topiramate may reduce the reinforcing effects and craving induced by higher cocaine doses. Low-dose cocaine might appear to have some enhancement of its stimulant properties in the presence of topiramate's prominent sedative effects.

GABA-based evaluation of neurologic conditions: MR spectroscopy

SUMMARY

GABA serves as a major neurotransmitter of the brain and functions mainly to inhibit neural excitatory activity. Disruption of the GABAergic processes appears to occur in various neurologic and psychiatric conditions, including epilepsy, mood disorders, motor disorders such as focal dystonia and stiff-person syndrome, sleep disorders, neuroplasticity, and drug and alcohol dependence. These concentration differences may be ascertained by using MR spectroscopy to provide information on the concentration of different metabolites. This review briefly discusses advances in MR spectroscopy methods and explores the application of this technique to detect changes in GABA due to disease processes and medication-induced effects.

MR spectroscopic studies of the brain in psychiatric disorders

The measurement of brain metabolites with magnetic resonance spectroscopy (MRS) provides a unique perspective on the brain bases of neuropsychiatric disorders. As a context for interpreting MRS studies of neuropsychiatric disorders, we review the characteristic MRS signals, the metabolic dynamics,and the neurobiological significance of the major brain metabolites that can be measured using clinical MRS systems. These metabolites include N-acetylaspartate(NAA), creatine, choline-containing compounds, myo-inositol, glutamate and glutamine, lactate, and gamma-amino butyric acid (GABA). For the major adult neuropsychiatric disorders (schizophrenia, bipolar disorder, major depression, and the anxiety disorders), we highlight the most consistent MRS findings, with an emphasis on those with potential clinical or translational significance. Reduced NAA in specific brain regions in schizophrenia, bipolar disorder, post-traumatic stress disorder, and obsessive–compulsive disorder corroborate findings of reduced brain volumes in the same regions. Future MRS studies may help determine the extent to which the neuronal dysfunction suggested by these findings is reversible in these disorders. Elevated glutamate and glutamine (Glx) in patients with bipolar disorder and reduced Glx in patients with unipolar major depression support models of increased and decreased glutamatergic function, respectively, in those conditions. Reduced phosphomonoesters and intracellular pH in bipolar disorder and elevated dynamic lactate responses in panic disorder are consistent with metabolic models of pathogenesis in those disorders. Preliminary findings of an increased glutamine/glutamate ratio and decreased GABA in patients with schizophrenia are consistent with a model of NMDA hypofunction in that disorder. As MRS methods continue to improve, future studies may further advance our understanding of the natural history of psychiatric illnesses, improve our ability to test translational models of pathogenesis, clarify therapeutic mechanisms of action,and allow clinical monitoring of the effects of interventions on brain metabolicmarkers

Proton MR spectroscopy-detectable major neurotransmitters of the brain: biology and possible clinical applications

Neurotransmitters are chemical substances that, by definition, allow communication between neurons and permit most neuronal-glial interactions in the CNS. Approximately 80% of all neurons use glutamate, and almost all interneurons use GABA. A third neurotransmitter, NAAG, modulates glutamatergic neurotransmission. Concentration changes in these molecules due to defective synthetic machinery, receptor expression, or errors in their degradation and metabolism are accepted causes of several neurologic disorders. Knowledge of changes in neurotransmitter concentrations in the brain can add useful information in making a diagnosis, helping to pick the right drug of treatment, and monitoring patient response to drugs in a more objective manner. Recent advances in (1)H-MR spectroscopy hold promise in providing a more reliable in vivo detection of these neurotransmitters. In this article, we summarize the essential biology of 3 major neurotransmitters: glutamate, GABA, and NAAG. Finally we illustrate possible applications of (1)H-MR spectroscopy in neuroscience research.

Purification and identification of a novel primitive secretory enzyme catalyzing the hydrolysis of imidazole-related dipeptides in the jawless vertebrate Lethenteron reissneri

Imidazole-related dipeptides, such as carnosine and anserine, occur widely in skeletal muscles of jawed vertebrates. All of the known enzymes that catalyze the hydrolysis of these dipeptides belong to the M20A metallopeptidase subfamily; two secretory enzymes, serum carnosinase (EC 3.4.13.20) and anserinase (EC 3.4.13.5), and one non-secretory enzyme, cytosolic nonspecific dipeptidase (EC 3.4.13.18). Here we report the enzymatic characterization and molecular identification of an unidentified enzyme, which catalyzes the hydrolysis of these dipeptides, from the skeletal muscle of Far Eastern brook lamprey (Lethenteron reissneri). A 60-kDa subunit protein of the enzyme was purified to near homogeneity. We cloned two M20A genes from the skeletal muscle of Far Eastern brook lamprey; one was a secretory-type gene encoding for the 60-kD protein, and another was a non-secretory-type gene presumably encoding for cytosolic nonspecific dipeptidase. Our findings indicate that the purified enzyme is a N-glycosylated secretory M20A dipeptidase distributed specifically in the jawless vertebrate group, and may be derived from a common ancestor gene between serum carnosinase and anserinase. We propose that this dipeptidase is a novel secretory M20A enzyme and is classified as neither serum carnosinase nor anserinase.

Acute topiramate differentially affects human aggressive responding at low vs. moderate doses in subjects with histories of substance abuse and antisocial behavior

Anticonvulsant drugs have demonstrated efficacy in the management of irritability and aggression in a variety of psychiatric populations. We examined the acute effects of topiramate on aggression using a laboratory model of human aggression (PSAP) in individuals at high risk for aggressive and violent behavior.Twelve subjects, on parole/probation and with an Axis-II personality disorder and/or a substance use disorder, received 100, 200, 300, and 400 mg in an ascending sequence, with intervening placebo doses.Subjects participated 2-3 days per week over 4-6 weeks. Due to cognitive side effects at 300 mg, two subjects only completed through the 200 mg dose. Topiramate produced an inverted U-shaped dose response curve, with increases in aggression peaking at 200 mg and a modest decrease at 400 mg. Statistical analysis revealed a polynomial trend for dose (p=0.001). The observed inverted U-shaped function in aggressive responding is consistent with non-human aggression studies of GABA-A modulators. Acute topiramate doses >400 mg may have anti-aggressive effects, but dose levels in the 200-300 mg range may produce increases in aggression and side effects.

The aspects and mechanisms of cognitive alterations in epilepsy: the role of antiepileptic medications

Epilepsy is a major health problem. Several studies suggest a significant influence of epilepsy and its treatment on dynamic and functional properties of brain activity. Epilepsy can adversely affect mental development, cognition, and behavior. Epileptic patients may experience reduced intelligence, attention, and problems in memory, language, and frontal executive functions. Neuropsychological, functional, and quantitative neuroimaging studies revealed that epilepsy affect the brain as a whole. Mechanisms of epilepsy-related cognitive dysfunction are poorly delineated. Cognitive deficits with epilepsy may be transient, persistent, or progressive. Transient disruption of cognitive encoding processes may occur with paroxysmal focal or generalized epileptic discharges, whereas epileptogenesis-related neuronal plasticity, reorganization, sprouting, and impairment of cellular metabolism are fundamental determinants for progressive cognitive deterioration. Also antiepileptic drugs (AEDs) have differential, reversible, and sometimes cumulative cognitive adverse consequences. AEDs not only reduce neuronal irritability but also may impair neuronal excitability, neurotransmitter release, enzymes, and factors critical for information processing and memory. The present article serves as an overview of recent studies in adult and childhood epilepsy literatures present in PubMed that highlighted cognitive evaluation in epilepsy field (publications till 2008 were checked). We also checked the reference lists of the retrieved studies for additional reports of relevant studies, in addition to our experience in this field. Our search revealed that although the aspects of cognitive dysfunction, risk factors, and consequences have been explored in many studies; however, the mechanisms of contribution of epilepsy-related variables, including AEDs, to patients' cognition are largely unexplored. In this review, we discussed the differential effect of AEDs in mature and immature brains and the known mechanisms underlying epilepsy and AEDs adverse effects on cognition. The nature, timing, course, and mechanisms of cognitive alteration with epilepsy and its medications are of considerable clinical and research implications.

Topiramate monotherapy in the treatment of newly or recently diagnosed epilepsy

BACKGROUND

The efficacy of topiramate (TPM) as an adjunctive treatment for epilepsy has been established in placebo-controlled clinical trials. Clinical trials of antiepileptic monotherapy usually evaluate low and high doses of study drug or compare study drug with another active agent.

OBJECTIVE

This article reviews available evidence for the use of TPM as monotherapy in patients with newly or recently diagnosed epilepsy.

METHODS

A search of MEDLINE, EMBASE, BIOSIS, SCISEARCH, and the Cochrane Database of Systematic Reviews (all years) for reports of controlled trials of TPM monotherapy in patients with recently diagnosed (within the previous 3 years) epilepsy was conducted in January 2008 using the terms topiramate, epilepsy, newly diagnosed, recently diagnosed, and monotherapy. Identified trials were included in the review if they were published in peer-reviewed journals and enrolled > or = 20 patients.

RESULTS

Three randomized, double-blind, controlled trials met the criteria for inclusion in the review. In a comparison of TPM 50 and 500 mg/d, the higher dose was associated with significantly greater freedom from seizures at 6 months compared with the lower dose (54% vs 39%, respectively; P = 0.02). The time to first seizure was significantly associated with mean plasma TPM concentrations (P = 0.015). In a comparison of TPM 50 and 400 mg/d, the time to first seizure was significantly longer with the higher dose compared with the lower dose (P<0.001, Kaplan-Meier analysis), and the probability of 12-month seizure freedom was significantly higher (76% vs 59%, respectively; P = 0.001). Again, the time to first seizure was significantly associated with mean plasma TPM concentrations (P = 0.029). In a comparative study of TPM 100 and 200 mg/d, carbamazepine 600 mg/d, and valproate 1250 mg/d, there was no significant difference in rates of 6-month seizure freedom with TPM 100 and 200 mg/d (49% and 44%, respectively), carbamazepine (44%), and valproate (44%). Adverse events in the 3 studies were similar between TPM dose groups, although the incidence generally increased with increasing doses, occurred early in treatment, and decreased with prolonged therapy. In a pooled analysis of the 3 trials, the most commonly occurring adverse events during dose titration were paresthesia (25%), fatigue (16%), dizziness (13%), somnolence (13%), and nausea (10%); the most frequent adverse events during maintenance therapy were headache (20%), decreased appetite (11%), and weight loss (11%).

CONCLUSION

In the 3 studies reviewed, TPM monotherapy was effective and generally well tolerated in patients with newly diagnosed epilepsy.

Low GABA concentrations in occipital cortex and anterior cingulate cortex in medication-free, recovered depressed patients

Studies using proton magnetic resonance spectroscopy (1H-MRS) indicate that unmedicated, acutely depressed patients have decreased levels of gamma-aminobutyric acid (GABA) in the occipital cortex. The aim of this study was to use 1H-MRS to determine if changes in occipital and frontal cortical GABA levels were present in patients with a history of depression who had recovered and were no longer taking medication. We used 1H-MRS to measure levels of GABA in both occipital cortex and anterior cingulate cortex/prefrontal cortex in medication-free, fully recovered subjects with a history of recurrent unipolar depression. Levels of GABA in both occipital and anterior cingulate cortex were significantly lower in recovered depressed subjects than healthy controls. Our data provide preliminary evidence that a history of recurrent depression is associated with decreased GABA levels in anterior cingulate cortex and occipital cortex. These changes could represent part of the neurobiological vulnerability to recurrent depressive episodes.

Long-term cognitive and mood effects of zonisamide monotherapy in epilepsy patients

This study was a prospective, randomized, open-label investigation of the long-term effects of zonisamide (ZNS) monotherapy on cognition and mood of patients with epilepsy. Forty-three patients with epilepsy received ZNS, with final dose groups of 100, 200, 300, and 400mg/day. Cognitive and mood tests were done twice, at baseline and 1 year after starting medication. Nine patients were withdrawn prior to their follow-up tests. Three patients (33%) dropped out during the titration period because of cognitive and mood problems. Thirty-four patients completed follow-up neuropsychological tests. After 1 year of treatment, 16 patients (47%) complained of cognitive deficits. Only 5 patients (15%) experienced mood changes. Although ZNS decreased seizure frequency and EEG abnormalities and did not elicit significant mood changes, it had negative effects on several cognitive tests. Worse performance on delayed word recall, Trail Making Test Part B, and verbal fluency was related to dose. In conclusion, ZNS has adverse effects on cognition even after 1 year of treatment.

Computational models of neuronal biophysics and the characterization of potential neuropharmacological targets

The identification and characterization of potential pharmacological targets in neurology and psychiatry is a fundamental problem at the intersection between medicinal chemistry and the neurosciences. Exciting new techniques in proteomics and genomics have fostered rapid progress, opening numerous questions as to the functional consequences of ligand binding at the systems level. Psycho- and neuro-active drugs typically work in nerve cells by affecting one or more aspects of electrophysiological activity. Thus, an integrated understanding of neuropharmacological agents requires bridging the gap between their molecular mechanisms and the biophysical determinants of neuronal function. Computational neuroscience and bioinformatics can play a major role in this functional connection. Robust quantitative models exist describing all major active membrane properties under endogenous and exogenous chemical control. These include voltage-dependent ionic channels (sodium, potassium, calcium, etc.), synaptic receptor channels (e.g. glutamatergic, GABAergic, cholinergic), and G protein coupled signaling pathways (protein kinases, phosphatases, and other enzymatic cascades). This brief review of neuromolecular medicine from the computational perspective provides compelling examples of how simulations can elucidate, explain, and predict the effect of chemical agonists, antagonists, and modulators in the nervous system.

Yoga Asana sessions increase brain GABA levels: a pilot study

OBJECTIVES

The aim of this study was to compare changes in brain gamma-aminobutyric (GABA) levels associated with an acute yoga session versus a reading session. It was hypothesized that an individual yoga session would be associated with an increase in brain GABA levels.

DESIGN

This is a parallel-groups design.

SETTINGS/LOCATION

Screenings, scan acquisitions, and interventions took place at medical school-affiliated centers.

SUBJECTS

The sample comprised 8 yoga practitioners and 11 comparison subjects.

INTERVENTIONS

Yoga practitioners completed a 60-minute yoga session and comparison subjects completed a 60-minute reading session.

OUTCOME MEASURES

GABA-to-creatine ratios were measured in a 2-cm axial slab using magnetic resonance spectroscopic imaging immediately prior to and immediately after interventions.

RESULTS

There was a 27% increase in GABA levels in the yoga practitioner group after the yoga session (0.20 mmol/kg) but no change in the comparison subject group after the reading session ( -0.001 mmol/kg) (t = -2.99, df = 7.87, p = 0.018).

CONCLUSIONS

These findings demonstrate that in experienced yoga practitioners, brain GABA levels increase after a session of yoga. This suggests that the practice of yoga should be explored as a treatment for disorders with low GABA levels such as depression and anxiety disorders. Future studies should compare yoga to other forms of exercise to help determine whether yoga or exercise alone can alter GABA levels.

Reduction in occipital cortex gamma-aminobutyric acid concentrations in medication-free recovered unipolar depressed and bipolar subjects

BACKGROUND

Studies using proton magnetic resonance spectroscopy (MRS) have indicated that unmedicated, acutely depressed patients have decreased levels of gamma-aminobutyric acid (GABA) in occipital cortex. Cortical levels of glutamate (Glu) may be increased, although these data are less consistent. The aim of this study was to use MRS to determine whether changes in GABA and Glu levels were present in patients with mood disorders who had recovered and were no longer taking medication.

METHODS

An [1H]-MRS was used to measure levels of GABA, of the combined concentration of Glu and glutamine (Gln), and of N-acetylaspartate (NAA) in occipital cortex in medication-free, fully recovered subjects with a history of recurrent unipolar depression (n = 15), bipolar disorder (n = 16), and a group of healthy controls (n = 18).

RESULTS

Occipital levels of GABA and NAA were significantly lower in recovered depressed and bipolar subjects than in healthy controls, whereas Glu +Gln concentrations were higher.

CONCLUSIONS

Our data suggest that recovered unmedicated subjects with a history of mood disorder have changes in cortical concentrations of GABA, NAA, and Glu +Gln. These biochemical abnormalities may be markers of a trait vulnerability to mood disorder, rather than neurochemical correlates of an abnormal mood state.

New Horizons in the development of antiepileptic drugs: Innovative strategies

The past decades have brought many advances to the treatment of epilepsy. However, despite the continued development and release of new antiepileptic drugs, many patients have seizures that do not respond to drug therapy or have related side effects that preclude continued use. Even in patients in whom pharmacotherapy is efficacious, current antiepileptic drugs do not seem to affect the progression or the underlying natural history of epilepsy. Furthermore, there is currently no drug available which prevents the development of epilepsy, e.g. after head trauma or stroke. Thus, there are at least four important goals for the future: (1) development of better antiepileptic ("anti-ictal") drugs with higher efficacy and tolerability to stop seizures compared to current medications; (2) better understanding of processes leading to epilepsy, thus allowing to create therapies aimed at the prevention of epilepsy in patients at risk; (3) development of disease-modifying therapies, interfering with progression of epilepsy, and (4) improved understanding of neurobiological mechanisms of pharmacoresistance, allowing to develop drugs for reversal or prevention of drug resistance. The third Workshop on New Horizons in the Development of Antiepileptic Drugs explored these four goals for improved epilepsy therapy, with a focus on innovative strategies in the search for better anti-ictal drugs, for novel drugs for prevention of epilepsy or its progression, and for drugs overcoming drug resistance in epilepsy. In this conference review, the current status of antiepileptic therapies under development is critically assessed, and innovative approaches for future therapies are highlighted.

Brain Homocarnosine and Seizure Control of Patients Taking Gabapentin or Topiramate

PURPOSE

To assess the relation between seizure control and brain homocarnosine and gamma-aminobutyric acid (GABA) levels of patients with complex partial seizures taking gabapentin (GBP) or topiramate (TPM) as adjunctive therapy.

METHODS

In vivo measurements of GABA and homocarnosine were made of a 14-cc volume in the occipital cortex by using (1)H spectroscopy with a 2.1-Tesla magnetic resonance spectrometer and an 8-cm surface coil. Poor seizure control was defined as more recent seizures than the median for the two groups of patients studied.

RESULTS

Homocarnosine levels were higher in patients with better seizure control than in those with poor control. No differences were found in the intracellular GABA levels between the patients who responded to GBP or TPM compared with those who did not.

CONCLUSIONS

In the visual neocortex, which is remote from the presumed seizure-onset zone, higher homocarnosine levels were associated with better seizure control in the patients taking GBP or TPM as adjunctive therapy; elevated intracellular GABA levels appeared to offer no additional protection.

Behaviour, cognition and epilepsy

Cognitive and behavioural impairments have been observed as a consequence even of single seizures. In individuals with high seizure frequency, such impairments may accumulate and have a much greater impact on daily life than hitherto suspected. In addition, the risk of behavioural impairments is increased for some seizure types, such as secondary generalized seizures. Moreover, for all epilepsy types, increased risk is associated with persistent or poorly controlled seizures. Clinical studies show that cognitive impairments induced by seizures are reversible for most seizure types when seizures are controlled adequately. Additionally, for some seizure types there may be a kind of time window within which impairments are reversible. Exceeding the time window may result in irreversible impairment. These studies suggest that antiepileptic drug treatment can thus protect against such secondary behavioural impairments or at least correct these when seizures are controlled. This emphasizes the need to achieve complete and early seizure control. On the contrary, all antiepileptic drugs have a detrimental effect on the central nervous system and may affect cognitive function, behaviour and mood to some extent. Some treatments may undo the beneficial effects of antiepileptic drug treatment by inducing new or other cognitive impairments. This once more illustrates the need for the emphasis of clinical practice to evolve from mere seizure control to a more comprehensive approach, in which the prevention of central cognitive effects and effects on daily life of both seizures and drugs is given due attention. Optimal management requires a careful balance between, on the one hand, the desire to reach early and maximal seizure control and, on the other, the need to avoid tolerability problems related to cognitive and behavioural impairments. This article reviews how this balance can be achieved for older and newer antiepileptic drugs.

The effect of topiramate on GABAB receptor, vesicular GABA transporter and paired-pulse inhibition in the gerbil hippocampus

To extend our understanding of the properties of topiramate (TPM), we investigated the effect of TPM on GABAergic transmission in the dentate gyrus of gerbil. TPM treatment (> or = 40 mg/kg) dramatically decreased GABA(B)R2, not GABA(B)R1, immunoreactivity in hilar interneurons. In contrast, TPM treatment increased vesicular GABA transporter immunoreactivity and the paired-pulse inhibition in the dentate gyrus of seizure prone gerbils. Furthermore, TPM effectively prevented the reduction of paired-pulse inhibition induced by baclofen treatment. These findings suggest that TPM may enhance GABA release in the dentate gyrus of gerbils by down-regulation of GABA(B) autoreceptor expression. Therefore, these properties of TPM may be another possible antiepileptic effect, which plays an important role in preventing the spread of seizure activity without proconvulsive effects.

Prefrontal GABA levels in cocaine-dependent subjects increase with pramipexole and venlafaxine treatment

RATIONALE

There is evidence that prefrontal lobe GABA levels are low in cocaine-dependent (CD) individuals, and treatment with GABA agonists decreases cocaine self-administration.

OBJECTIVES

The aim of the study is to measure changes in GABA levels in CD subjects at baseline and after 8 weeks of treatment with pramipexole, venlafaxine, or placebo.

METHODS

CD subjects enrolled in a treatment trial for cocaine dependence were recruited for this proton (1H) magnetic resonance spectroscopy (MRS) study. GABA levels in the prefrontal lobe were measured before and after treatment.

RESULTS

Mean percentage changes in GABA levels were as follows: pramipexole +17.0+/-28.0%, venlafaxine +13.0+/-11.0%, and placebo -2.1+/-19.5%. Pramipexole-treated subjects had significantly increased brain GABA levels compared to placebo (p=0.031). Venlafaxine treatment was nonsignificantly associated with increased GABA levels compared to placebo (p=0.16). The overall statistical model for the effect of drug treatment vs placebo on brain GABA levels, including adjustment for baseline levels, was highly significant (p=0.002). Despite significant changes in GABA levels, there were no significant differences in the number of urine samples positive for cocaine metabolites.

CONCLUSIONS

This study demonstrates that 1H MRS can measure changes in GABA levels following pharmacologic treatment. The increase in GABA levels, although significant, is modest compared to other MRS studies of depression or epilepsy associated with clinical improvements. The failure to see larger increases in GABA levels and an associated reduction in cocaine consumption may reflect the relatively low doses of medication used.

Neuroimaging of epilepsy: therapeutic implications

Neuroimaging has important applications in the diagnosis and treatment of patients with seizures and epilepsy. Having replaced computed tomography (CT) in many situations, MRI is the preferred imaging technique for patients with epilepsy. Advances in radionuclide-based techniques such as single-photon emission CT/positron emission tomography and electromagnetic source imaging with magnetoencephalography are providing new insights into the pathophysiology of epilepsy. In addition, techniques such as magnetic resonance spectroscopy are beginning to impact treatment. In this review, I discuss how these techniques are used in clinical practice but more importantly, how imaging findings play an increasing role in neurotherapeutics.

1H-MR-Spektroskopie

Techniques and methods of clinical (1)H-MR spectroscopy are described in this manuscript. The role of (1)H-MRS in the multimodal focus analysis of temporal lobe epilepsy (TLE) is illustrated with special respect to focus lateralization and differentiation between mesial and lateral (neocortical) TLE. Additionally the application of (1)H-MRS for evaluating postoperative outcome and monitoring conservative antiepileptic treatment schedules is summarized.

Intentional Topiramate Ingestion in an Adolescent Female

OBJECTIVE:

To describe an intentional topiramate ingestion by an adolescent and warn of the potential for topiramate abuse.

CASE SUMMARY:

A 17-year-old female intentionally ingested approximately eight 100-mg topiramate tablets for the purpose of “getting high.” Soon after ingestion, she was found at school obtunded and nonresponsive. Upon transfer to the emergency department, she became combative and aggressive with evolving neurologic abnormalities including incoherence, confusion, disorientation, and significant speech impairments including echolalia. Approximately 24 hours after ingestion, the patient had completely recovered without requiring specific treatment or experiencing sequelae.

DISCUSSION:

The clinical effects following acute topiramate intoxication appear consistent with the drug's known pharmacologic properties. There are few other reports of topiramate ingestions and most cases have had mild outcomes.

CONCLUSIONS:

Due to the multifactorial effects topiramate may have upon the central nervous system and its anorectic effect, abuse of this drug by adolescents should be considered upon presentation of an adolescent with mental status changes.

Effect of topiramate on seizures and respiratory dysrhythmia in Rett syndrome

Rett syndrome, a neurodevelopmental disorder, manifests in the first few years of life with developmental arrest, stereotyped behaviors, and respiratory abnormalities. Seizures occur in 70 to 80% of patients. Clinical drug trials have not demonstrated the superiority of any specific antiepilepsy drug. We report our experience with topiramate in eight patients with Rett syndrome. Topiramate was initiated as monotherapy in two patients and as adjunctive therapy in six patients. Seven patients had improved seizure control. Respiratory abnormalities improved by 50 to 75% in two patients and by 20 to 50% in two others. In our cohort, seven of eight patients showed improvement in seizure control and/or respiratory abnormalities on topiramate. Topiramate was well tolerated. The effect of topiramate, a broad-spectrum drug, could be due to its gamma-aminobutyric acid (GABA)ergic and glutaminergic effects, both systems thought to be disordered in Rett syndrome.

Down syndrome and epilepsy: a nutritional connection?

Non-Asian individuals with Down syndrome are much more likely to develop epileptic seizure disorders than individuals without Down syndrome. Examination of nutrient and metabolite levels in patients with these two seemingly disparate disorders reveals numerous similarities. Compared to individuals without these disorders, individuals with Down syndrome and individuals with seizures may have lower levels of vitamin A, vitamin B1, folate, vitamin B12, vitamin C, magnesium, manganese, selenium, zinc, carnitine, carnosine, choline, and possibly serine. Excesses of copper, cysteine, phenylalanine, and superoxide dismutase are also sometimes encountered in both disorders. In addition to common nutritional lower levels and excesses, disorders of metabolism involving vitamin B6, vitamin D, calcium, and tryptophan may play a common role. This paper hypothesizes that nutritional factors may account for the high joint occurrence of these conditions. Further examination of these data may provide insights into nutritional, metabolic and pharmacological treatments for both conditions.