Variant Transthyretin Amyloidosis (ATTRv) in Hungary: First Data on Epidemiology and Clinical Features.

BACKGROUND: Variant transthyretin amyloidosis (ATTRv) is an autosomal dominant inherited disease, where the mutation of the transthyretin gene (TTR) results in the deposition of pathogenic protein fibrils in various tissues. The mutation type influences the clinical course. Until now, no data were available on the genotype, phenotype, and prevalence of Hungarian ATTRv patients. The aim of our study was to assess the prevalence, regional distribution, genotypes, and phenotypes of Hungarian patients with ATTRv. METHODS: With the collaboration of Hungarian regional and university centers, we identified patients diagnosed with ATTRv. We also searched prior publications for case studies of Hungarian ATTRv patients. RESULTS: 40 individuals in 23 families with ATTRv were identified within the borders of Hungary. At the time of the diagnosis, 24 of them were symptomatic. The two most common mutations were ATTRHis88Arg (nine families) and ATTRIle107Val (8 families). ATTRVal30Met was demonstrated in 2 families, and ATTRVal122del, ATTRPhe33Leu, ATTRIle84Ser, and ATTRAsp18Gly in one family each. The median age of the symptomatic patients at the time of clinical diagnosis was 65 years. The most common clinically significant organ involvement was restrictive cardiomyopathy, found in 24 patients. Polyneuropathy was diagnosed in 20 patients. A total of 19 patients showed a mixed phenotype. The leading symptom was heart failure in 8 cases (3 of them had only cardiac symptoms), polyneuropathy in 11 cases (all of them also had cardiac symptoms), and equally severe cardiac and neuropathy symptoms were present in 3 cases. Out of 24 symptomatic patients, 10 received targeted pharmacological therapy. The follow-up period ranged from 1 to 195 months. At the time of the retrospective analysis, 12 patients had already died, and 1 patient underwent heart transplantation. CONCLUSIONS: As TTR genotype influences the phenotype and clinical course of ATTRv, it is important to know the regional data. In Hungary, ATTRHis88Arg and ATTRIle107Val are the most common mutations in ATTRv, both presenting with mixed phenotype, but the median age at the time of the diagnosis is 9 years lower in patients with ATTRHis88Arg than in patients with ATTRIle107Val.

Correlation of GAA Genotype and Acid-α-Glucosidase Enzyme Activity in Hungarian Patients with Pompe Disease.

Pompe disease is caused by the accumulation of glycogen in the lysosomes due to a deficiency of the lysosomal acid-α-glucosidase (GAA) enzyme. Depending on residual enzyme activity, the disease manifests two distinct phenotypes. In this study, we assess an enzymatic and genetic analysis of Hungarian patients with Pompe disease. Twenty-four patients diagnosed with Pompe disease were included. Enzyme activity of acid-α-glucosidase was measured by mass spectrometry. Sanger sequencing and an MLPA of the GAA gene were performed in all patients. Twenty (83.33%) patients were classified as having late-onset Pompe disease and four (16.66%) had infantile-onset Pompe disease. Fifteen different pathogenic GAA variants were detected. The most common finding was the c.-32-13 T > G splice site alteration. Comparing the α-glucosidase enzyme activity of homozygous cases to the compound heterozygous cases of the c.-32-13 T > G disease-causing variant, the mean GAA activity in homozygous cases was significantly higher. The lowest enzyme activity was found in cases where the c.-32-13 T > G variant was not present. The localization of the identified sequence variations in regions encoding the crucial protein domains of GAA correlates with severe effects on enzyme activity. A better understanding of the impact of pathogenic gene variations may help earlier initiation of enzyme replacement therapy (ERT) if subtle symptoms occur. Further information on the effect of GAA gene variation on the efficacy of treatment and the extent of immune response to ERT would be of importance for optimal disease management and designing effective treatment plans.

[Advanced Parkinson's disease characteristics in clinical practice: Results from the OBSERVE-PD study and sub-analysis of the Hungarian data]. / Az elôrehaladott Parkinson-kór jellemzôi a klinikai gyakorlatban: az OBSERVE-PD vizsgálat eredményei és a magyarországi alcsoport elemzése.

BACKGROUND AND PURPOSE: The majority of patients with advanced Parkinson's disease are treated at specialized movement disorder centers. Currently, there is no clear consensus on how to define the stages of Parkinson's disease; the proportion of Parkinson's patients with advanced Parkinson's disease, the referral process, and the clinical features used to characterize advanced Parkinson's disease are not well delineated. The primary objective of this observational study was to evaluate the proportion of Parkinson's patients identified as advanced patients according to physician's judgment in all participating movement disorder centers across the study. Here we evaluate the Hungarian subset of the participating patients. METHODS: The study was conducted in a cross-sectional, non-interventional, multi-country, multi-center format in 18 countries. Data were collected during a single patient visit. Current Parkinson's disease status was assessed with Unified Parkinson's Disease Rating Scale (UPDRS) parts II, III, IV, and V (modified Hoehn and Yahr staging). Non-motor symptoms were assessed using the PD Non-motor Symptoms Scale (NMSS); quality of life was assessed with the PD 8-item Quality-of-Life Questionnaire (PDQ-8). Parkinson's disease was classified as advanced versus non-advanced based on physician assessment and on questions developed by the Delphi method. RESULTS: Overall, 2627 patients with Parkinson's disease from 126 sites were documented. In Hungary, 100 patients with Parkinson's disease were documented in four movement disorder centers, and, according to the physician assessment, 50% of these patients had advanced Parkinson's disease. Their mean scores showed significantly higher impairment in those with, versus without advanced Parkinson's disease: UPDRS II (14.1 vs. 9.2), UPDRS IV Q32 (1.1 vs. 0.0) and Q39 (1.1 vs. 0.5), UPDRS V (2.8 vs. 2.0) and PDQ-8 (29.1 vs. 18.9). CONCLUSION: Physicians in Hungarian movement disorder centers assessed that half of the Parkinson's patients had advanced disease, with worse motor and non-motor symptom severity and worse QoL than those without advanced Parkinson's disease. Despite being classified as eligible for invasive/device-aided treatment, that treatment had not been initiated in 25% of these patients.

[The long-term follow-up of enzyme replacement treatment in late onset Pompe disease]. / A késoi kezdetu Pompe-kórban szenvedok enzimpótló kezelésének hosszú távú követése.

Pompe disease (PD) is a rare lysosomal disease caused by the deficient activity of acid alpha-glucosidase (GAA) enzyme due to mutations in the GAA gene. The enzymatic deficiency leads to the accumulation of glycogen within the lysosomes. Clinically, the disease has been classically classified in infantile and childhood/adult forms. Presently cc. close to 600 mutations distributed throughout the whole gene have been reported. The c.-32-13T>G splice mutation that is very common in patients of Caucasian origin affected by the childhood/adult form of the disease, with an allelic frequency close to 70%. Enzyme replacement treatment (ERT) is available for the patients with Pompe disease (Myozyme). In this paper, we are presenting the long term follow up of 13 adult onset cases treated more than 5 years. The longest follow up was 15 years. To evaluate the treatment efficacy, the 6 minutes walking test (6MWT) and the respiratory functions were monitored annually. The analysis revealed that at the beginning of ERT for 3-4 years the 6MWT had been generally increasing, then it declined, and after 10 years it was lower in 77% of the cases than it had been at the start of the treatment. In 23% of the cases the 6MWT increased during the follow up time. Only one of the patients become wheelchair dependent during the follow-up period. The respiratory function showed similar results especially in supine position. A high degree of variability was observed among patients in their responses to the treatment, which only partially associated with the antibody titer against the therapeutic protein. The efficacy of the ERT was associated with the type of the disease causing mutation, the baseline status of the disease, the lifestyle and the diet of the patient. The long-term follow up of the patients with innovative orphan drugs is necessary to really understand the value of the treatment and the need of the patients.

CANOMAD syndrome with respiratory failure.

CANOMAD (chronic ataxic neuropathy, ophthalmoplegia, M-protein agglutination, disialosyl antibodies) syndrome is a rare polyneuropathy. IgM paraproteins react with ganglioside-containing disialylated epitopes resulting in dorsal root ganglionopathy and B-lymphocyte infiltration of cranial and peripheral nerves. Clinical features include ataxia, slight muscle weakness, areflexia, sensory- and cranial nerve symptoms. Case studies have reported the efficacy of rituximab and intravenous immunoglobulin (IVIg) treatments. We present the case of a 57-year-old man, who had difficulty walking, with numbness and clumsiness in all limbs. He had areflexia, vibratory sensation loss and ataxia. Laboratory tests showed IgM monoclonal components and disialosyl antibodies in the serum. Nerve conduction studies indicated severe sensorimotor demyelinating polyneuroradiculopathy. Despite IVIg and rituximab treatments, the patient's disease course gradually worsened and he died of respiratory failure. Neuropathological examination revealed dorsal column- and dorsal root atrophy with mixed mononuclear cell infiltration. This article aims to draw attention to this syndrome, and the use of early potent immunosuppressive treatment to improve patients' quality of life.

NKX2-1 New Mutation Associated With Myoclonus, Dystonia, and Pituitary Involvement.

Background:NKX2-1 related disorders (also known as brain-lung-thyroid syndrome or benign hereditary chorea 1) are associated with a wide spectrum of symptoms. The core features are various movement disorders, characteristically chorea, less frequently myoclonus, dystonia, ataxia; thyroid disease; and lung involvement. The full triad is present in 50% of affected individuals. Numerous additional symptoms may be associated, although many of these were reported only in single cases. Pituitary dysfunction was ambiguously linked to NKX2-1 haploinsufficiency previously. Case Presentation: We examined two members of a family with motor developmental delay, mixed movement disorder (myoclonus, dystonia and chorea) and endocrinological abnormalities (peripheric thyroid disease, and pituitary hormone deficiencies). Dystonia predominated at the father, and myoclonus at the daughter. The father had hypogonadotropic hypogonadism, while the daughter was treated with growth hormone deficiency. Both patients had empty sella on MRI. Candidate gene analyses were negative. Exome sequencing detected a pathogenic stop variation (NM_003317:c.338G>A, p.Trp113*) in the NKX2-1 gene. Conclusions: This case study has two highlights. (1) It draws attention to possible pituitary dysfunction in brain-lung-thyroid syndrome, and provide further evidences that this might be linked to loss of function of the NKX2-1 gene. (2) It underscores the importance of considering NKX2-1 related disorders in the differential diagnosis of myoclonus dystonia.

Levodopa/carbidopa intestinal gel can improve both motor and non-motor experiences of daily living in Parkinson's disease: An open-label study.

BACKGROUND: Levodopa/carbidopa intestinal gel therapy (LCIG) can efficiently improve several motor and non-motor symptoms of advanced Parkinson's disease (PD). The recently developed Movement Disorder Society-sponsored Unified Parkinson's Disease Rating Scale (MDS-UPDRS) improved the original UPDRS making it a more robust tool to evaluate therapeutic changes. However, previous studies have not used the MDS-UPDRS and the Unified Dyskinesia Rating Scale (UDysRS) to assess the efficacy of LCIG. OBJECTIVES: Our aim was to determine if the MDS-UPDRS and UDysRS could detect improvement in the experiences of daily living following 1-year LCIG treatment. METHODS: In this prospective, multicenter, open-label study, 34 consecutive patients undergoing LCIG treatment were enrolled. Patients were examined twice: prior to LCIG initiation and 12 months later. Impact of PD-related symptoms and dyskinesia was assessed by the MDS-UPDRS and UDysRS. RESULTS: Non-motor Experiences of Daily Living part of MDS-UPDRS improved from 20 (median, interquartile-range, IQR:14-23) to 16 points (median, IQR:12-20, p = 0.044) and the Motor Experiences of Daily Living ameliorated from 24 (median, IQR:20-29) to 18 points (median, IQR:13-25, p = 0.025). Health-related quality of life, measured by PDQ-39, also improved from 35.4 (median, IQR:26.9-50.3) to 27.0 (median, IQR:21.3-31.4) points (p = 0.003). The total score of UDysRS decreased from 47 (median, IQR:36-54) to 34 (median, IQR:21-45) points (p = 0.003). CONCLUSIONS: As far as the authors are aware of, our paper is the first to evaluate the impact of LCIG on dyskinesia by the means of UDysRS. Changes in MDS-UPDRS and UDysRS confirm that LCIG treatment can efficiently improve experiences of daily living in advanced PD.

Monoamine Oxidase B Inhibitors in Parkinson's Disease.

BACKGROUND: Parkinson's disease (PD) is a neurodegenerative disorder with a prevalence increasing with age. Oxidative stress and glutamate toxicity are involved in its pathomechanism. There are still many unmet needs of PD patients, including the alleviation of motor fluctuations and dyskinesias, and the development of therapies with neuroprotective potential. OBJECTIVE: To give an overview of the pharmacological properties, the efficacy and safety of the monoamine oxidase B (MAO-B) inhibitors in the treatment of PD, with special focus on the results of randomized clinical trials. METHOD: A literature search was conducted in PubMed for 'PD treatment', 'MAO-B inhibitors', 'selegiline', 'rasagiline', 'safinamide' and 'clinical trials' with 'MAO-B inhibitors' in 'Parkinson' disease'. RESULTS: MAO-B inhibitors have a favorable pharmacokinetic profile, improve the dopamine deficient state and may have neuroprotective properties. Safinamide exhibits an anti-glutamatergic effect as well. When applied as monotherapy, MAO-B inhibitors provide a modest, but significant improvement of motor function and delay the need for levodopa. Rasagiline and safinamide were proven safe and effective when added to a dopamine agonist in early PD. As add-on to levodopa, MAO-B inhibitors significantly reduced off-time and were comparable in efficacy to COMT inhibitors. Improvements were achieved as regards certain non-motor symptoms as well. CONCLUSION: Due to the efficacy shown in clinical trials and their favorable side-effect profile, MAO-B inhibitors are valuable drugs in the treatment of PD. They are recommended as monotherapy in the early stages of the disease and as add-on therapy to levodopa in advanced PD.

Left ventricular deformation abnormalities in a patient with calpainopathy-a case from the three-dimensional speckle-tracking echocardiographic MAGYAR-Path Study.

Calpainopathy or limb-girdle muscular dystrophy type 2A (LGMD2A) is the most common type of autosomal recessive limb-girdle muscular dystrophies. The disease is caused by mutations in the CAPN3 gene encoding calpain, a protein involved in muscle membrane remodeling and repair. This paper gives an overview of the genetic background, clinical course, and diagnosis of the disease, and presents the first case of calpainopathy in which cardiac deformation mechanics was investigated. Three-dimensional speckle-tracking echocardiography (3DSTE) demonstrated reduced left ventricular (LV) strains and increased LV apical rotation and twist, suggestive of asymptomatic subclinical LV dysfunction. Cardiac involvement has not been previously reported in calpainopathy.

Intravenous immunoglobulin: pharmacological properties and use in polyneuropathies.

INTRODUCTION: Intravenous immunoglobulin (IVIg) is increasingly used for the treatment of autoimmune and systemic inflammatory diseases with both licensed and off-label indications. The mechanism of action is complex and not fully understood, involving the neutralization of pathological antibodies, Fc receptor blockade, complement inhibition, immunoregulation of dendritic cells, B cells and T cells and the modulation of apoptosis. Areas covered: First, this review describes the pharmacological properties of IVIg, including the composition, mechanism of action, and adverse events. The second part gives an overview of some of the immune-mediated polyneuropathies, with special focus on the pathomechanism and clinical trials assessing the efficacy of IVIg. A literature search on PubMed was performed using the terms IVIg, IVIg preparations, side effects, mechanism of action, clinical trials, GBS, CIDP. Expert opinion: Challenges associated with IVIg therapy and the treatment possibilities for immune-mediated polyneuropathies are discussed. The availability of IVIg is limited, the expenses are high, and, in several diseases, a chronic therapy is necessary to maintain the immunomodulatory effect. The better understanding of the mechanism of action of IVIg could open the possibility of the development of disease-specific, targeted immune therapies.

Alzheimer's disease, astrocytes and kynurenines.

Alzheimer's disease (AD) is an age-related neurodegenerative disease and the most common cause of dementia. The etiology of AD is not entirely clear and despite the increasing knowledge regarding the pathomechanism, no effective disease-modifying therapy is yet available. Astrocytes earlier presumed to serve merely supportive roles for the neuronal network, have recently been shown to play an active role in the synaptic dysfunction, impairment of homeostasis, inflammation as well as excitotoxicity in relation to AD pathology. This review focuses on the pathomechanism of AD with special attention to the role of the astrocytes, excitotoxicity and the alterations in the kynurenine metabolism in the development of the disease. The correction of the neuroprotective/neurotoxic imbalance in the kynurenine pathway may represent a novel target for pharmaceutical interventions in dementia related to neurodegenerative disorders.

HYPERGLYCAEMIC HEMIBALLISMUS: IMPLICATIONS FROM CONNECTIVITY ANALYSIS FOR COGNITIVE IMPAIRMENTS.

Hyperglycaemia induced movement disorders, such as hemiballism are rare disorders. The syndrome is characterised by the triad of hemiballism, contralateral T1-hyperintense striatal lesion and non-ketotic hyperglycaemia. Here we report a patient with untreated diabetes presenting with acute onset of hemiballism. MRI revealed T1 hyperintensity of the head of the caudate nucleus and the anterior putamen. The patient also had acantocytosis. Based on the detailed examination of the neuroradiological results and earlier findings we will discuss the pathomechanism. Based on previous findings microhemorrhages, extensive mineralisation, gemistocytic astrocytosis might play a role in the development of the imaging signs. The connectivity pattern of the striatal lesion showed extensive connections to the frontal cortex. In coexistence with that the most severe impairment was found on the phonemic verbal fluency task measuring frontal executive functions.

Safinamide for the treatment of Parkinson's disease.

INTRODUCTION: Parkinson's disease (PD) is a neurodegenerative disorder characterized by the loss of dopaminergic neurons in the substantia nigra pars compacta. Non-dopaminergic neurotransmitter systems are also involved in its pathomechanism. The aim of the treatment is to improve the dopamine-deficient state and to alleviate the motor and the non-motor symptoms. Safinamide is an α-aminoamide derivative with a combined, dopaminergic and non-dopaminergic mode of action. Phase III clinical trials with safinamide, as add-on therapy to a dopamine agonist (DAA) and to levodopa (LD) in early and advanced stage PD, respectively, demonstrated an improvement of the motor symptoms. AREAS COVERED: The review discusses the pharmacokinetic and pharmacodynamic properties of safinamide and provides an overview of the clinical trials conducted with safinamide in PD. A literature search was made in PubMed for safinamide, safinamide pharmacokinetics, PD treatment and monoamine oxidase-B inhibitors, and in PubMed and on the ClinicalTrials.gov site for clinical trials with safinamide in PD. EXPERT OPINION: The place of safinamide in the therapy of PD is yet to be determined. However, the authors believe that safinamide is a valuable drug in the treatment of PD treatment with favorable pharmacokinetic and side-effect profiles. Data so far suggest that it can be used beneficially as add-on therapy both to DAAs in early PD and to LD in the later stages of the disease.

Clinical implications of irregular ADMET properties with levodopa and other antiparkinson's drugs.

INTRODUCTION: Parkinson's disease is a neurodegenerative disorder characterized by the loss of striatal dopaminergic neurons. Besides the improvement of the dopaminergic loss, the treatment focuses on non-dopaminergic medication targeting motor and non-motor symptoms, and on the development of neuroprotective medication. A good knowledge of the properties of the compounds used is essential not only for those involved in pharmacological research but also for those who treat Parkinson's disease patients, facing their still many unmet needs. AREAS COVERED: The review discusses the pharmacokinetic properties of levodopa (LD) and factors influencing them, the pharmacodynamics of LD and approaches with the aim of improving this, covering some of the other antiparkinson medications available. Among the non-dopaminergic agents, it focuses on research on kynurenines. A literature search was made in PubMed for Parkinson's disease treatment, LD, LD absorption, LD pharmacokinetics, continuous dopaminergic stimulation, LD-carbidopa intraintestinal gel therapy, dopamine agonists and monoamine oxidase-B inhibitors. EXPERT OPINION: Various factors can cause irregularities in the pharmacokinetics of LD, with interconnected consequences on its therapeutic effect. Its long-term use is associated with the development of motor complications; this is explained mostly by pharmacodynamic and also by pharmacokinetic properties, the latter gaining importance in the advanced stages of the disease.

[Experience with levodopa/carbidopa intestinal gel in the treatment of advanced Parkinson's disease in Hungary]. / A levodopa/carbidopa intestinalis gél kezelés magyarországi tapasztalatai elorehaladott Parkinson-kórban.

In the advanced Parkison's disease (PD) the late complications of levodopa therapy have to be considered: motor and/or non-motor fluctuations with or without disturbing dyskinesias. The non-motor fluctuations often influence the quality of life (QoL) in a much more negative way compared with the motor symptoms. In the treatment of advanced PD there are several device-aided methods - deep brain stimulation, apomorphine pump, levodopa/carbidopa intestinal gel (LCIG) - to improve the symptoms, the QoL, sometimes even in an individual, tailored custom form. The LCIG therapy was introduced in Hungary in 2011. Here we summarize the data of our patients: we have tested almost 60 patients and in 43 cases we have started this treatment. We analyze the duration of illness, levodopa therapy, motor and non-motor fluctuation of patients and present our experiences with the test phase and the chronic LCIG therapy via PEG/PEJ implantation. We paid attention to the surgery and device - depending side effects. Our experiences are similar to the international data. In patients selection ,,the right treatment, to the right patient, in the right time" is of importance.

[Inclusion body myositis--a rarely recognized disorder]. / Zárványtestes myositis--egy ritikán felismert betegség.

Inclusion body myositis is the most common disabling inflammatory myopathy in the elderly. It is more frequent in men and after the age of 50 years. Inflammatory and degenerative features coexist. There is a T-cell mediated autoimmunity driven by in situ clonally expanded cytotoxic CD8-positive T-cells invading non-necrotic muscle fibres expressing MHC-I antigen. The hallmarks of degeneration are the deposition of protein aggregates and the formation of vesicles. The course of the disease is slow and the diagnosis is usually set after several years. The muscle weakness and wasting is assymetric, affecting predominantly distal muscles of the upper extremity and proximal muscles of the legs. The signs and clinical course can be characteristic, but the diagnosis is established by muscle biopsy. There is currently no evidence based effective treatment for sIBM. Prednisone, azathioprine, methotrexate, cyclosporine and IFN-beta failed. Oxandrolon did not improve symptoms. Treatment with intravenous immunglobuline (IVIG) induced in some patients a transient improvement of swallowing and of muscle strenght, but the overall study results were negative. A T-cell depleting monoclonal antibody (alemtuzumab), in a small uncontrolled study slowed down disease progression for a six-month period. Repeated muscle biopsies showed the reduction of T-cells in the muscle and the suppression of some degeneration associated molecules. An effective therapeutic mean should act on both aspects of the pathomechanism, on the inflammatory and the degenerative processes as well.

Target identification for stereotactic thalamotomy using diffusion tractography.

BACKGROUND: Stereotactic targets for thalamotomy are usually derived from population-based coordinates. Individual anatomy is used only to scale the coordinates based on the location of some internal guide points. While on conventional MR imaging the thalamic nuclei are indistinguishable, recently it has become possible to identify individual thalamic nuclei using different connectivity profiles, as defined by MR diffusion tractography. METHODOLOGY AND PRINCIPAL FINDINGS: Here we investigated the inter-individual variation of the location of target nuclei for thalamotomy: the putative ventralis oralis posterior (Vop) and the ventral intermedius (Vim) nucleus as defined by probabilistic tractography. We showed that the mean inter-individual distance of the peak Vop location is 7.33 mm and 7.42 mm for Vim. The mean overlap between individual Vop nuclei was 40.2% and it was 31.8% for Vim nuclei. As a proof of concept, we also present a patient who underwent Vop thalamotomy for untreatable tremor caused by traumatic brain injury and another patient who underwent Vim thalamotomy for essential tremor. The probabilistic tractography indicated that the successful tremor control was achieved with lesions in the Vop and Vim respectively. CONCLUSIONS: Our data call attention to the need for a better appreciation of the individual anatomy when planning stereotactic functional neurosurgery.

Established therapies and novel targets in the treatment of Parkinson's disease.

Parkinson's disease affects more than 1% of individuals older than 60 years of age. The gold standard of its symptomatic treatment is levodopa therapy, which in time leads to motor fluctuations and dyskinesia due to noncontinuous receptor stimulation. Dopamine agonists and monoamine oxidase-B inhibitors are recommended as initial therapy, but they are less effective in the advanced stages of the disease. Treatment should be individualized for the patient, dependent on the stage, with attention to nonmotor symptoms. No effective neuroprotective therapy for Parkinson's disease is yet available, and there is currently substantial interest in the development of new nondopaminergic agents. Analogs of kynurenic acid and inhibitors of the enzymes involved in the synthesis of quinolinic acid may exert a neuroprotective effect.