The concentrations of GABA, 5-HIAA and HVA in the cerebrospinal fluid of children with infantile spasms and the effects of ACTH treatment

IGF-1 impacts neocortical interneuron connectivity in epileptic spasm generation and resolution

Little is known about the mechanisms that generate epileptic spasms following perinatal brain injury. Recent studies have implicated reduced levels of Insulin-like Growth Factor 1 (IGF-1) in these patients' brains. Other studies have reported low levels of the inhibitory neurotransmitter, GABA. In the TTX brain injury model of epileptic spasms, we undertook experiments to evaluate the impact of IGF-1 deficiencies on neocortical interneurons and their role in spasms. Quantitative immunohistochemical analyses revealed that neocortical interneurons that express glutamic acid decarboxylase, parvalbumin, or synaptotagmin 2 co-express IGF-1. In epileptic rats, expression of these three interneuron markers were reduced in the neocortex. IGF-1 expression was also reduced, but surprisingly this loss was confined to interneurons. Interneuron connectivity was reduced in tandem with IGF-1 deficiencies. Similar changes were observed in surgically resected neocortex from infantile epileptic spasms syndrome (IESS) patients. To evaluate the impact of IGF-1 deficiencies on interneuron development, IGF-1R levels were reduced in the neocortex of neonatal conditional IGF-1R knock out mice by viral injections. Four weeks later, this experimental maneuver resulted in similar reductions in interneuron connectivity. Treatment with the IGF-1 derived tripeptide, (1-3)IGF-1, abolished epileptic spasms in most animals, rescued interneuron connectivity, and restored neocortical levels of IGF-1. Our results implicate interneuron IGF-1 deficiencies, possibly impaired autocrine IGF-1 signaling and a resultant interneuron dysmaturation in epileptic spasm generation. By restoring IGF-1 levels, (1-3)IGF-1 likely suppresses spasms by rescuing interneuron connectivity. Results point to (1-3)IGF-1 and its analogues as potential novel disease-modifying therapies for this neurodevelopmental disorder.

Biochemical mechanisms in pathogenesis of infantile epileptic spasm syndrome

The molecular mechanisms leading to infantile epileptic spasm syndrome (IESS) remain obscure. The only common factor seems to be that the spasms are restricted to a limited period of infancy, during a certain maturational state. Here the current literature regarding the biochemical mechanisms of brain maturation in IESS is reviewed, and various hypotheses of the pathophysiology are put together. They include: (1) imbalance of inhibitory (NGF, IGF-1, ACTH, GABA) and excitatory factors (glutamate, nitrites) which distinguishes the different etiological subgroups, (2) abnormality of the hypothalamic pituitary adrenal (HPA) axis linking insults and early life stress, (3) inflammation (4) yet poorly known genetic and epigenetic factors, and (5) glucocorticoid and vigabatrin action on brain development, pinpointing at molecular targets of the pathophysiology from another angle. An altered maturational process may explain why so many, seemingly independent etiological factors lead to the same clinical syndrome and frequently to developmental delay. Understanding these factors can provide ideas for novel therapies.

Ocular dysfunctions and toxicities induced by antiepileptic medications: Types, pathogenic mechanisms, and treatment strategies

INTRODUCTION

Ocular dysfunctions and toxicities induced by antiepileptic drugs (AEDs) are rarely reviewed and not frequently received attention by treating physicians compared to other adverse effects (e.g. endocrinologic, cognitive and metabolic). However, some are frequent and progressive even in therapeutic concentrations or result in permanent blindness. Although some adverse effects are non-specific, others are related to the specific pharmacodynamics of the drug. Areas covered: This review was written after detailed search in PubMed, EMBASE, ISI web, SciELO, Scopus, and Cochrane Central Register databases (from 1970 to 2019). It summarized the reported ophthalmologic adverse effects of the currently available AEDs; their risks and possible pathogenic mechanisms. They include ocular motility dysfunctions, retinopathy, maculopathy, glaucoma, myopia, optic neuropathy, and impaired retinal vascular autoregulation. In general, ophthalmo-neuro- or retino-toxic adverse effects of AEDs are classified as type A (dose-dependent), type B (host-dependent or idiosyncratic) or type C which is due to the cumulative effect from long-term use. Expert opinion: Ocular adverse effects of AEDs are rarely reviewed although some are frequent or may result in permanent blindness. Increasing knowledge of their incidence and improving understanding of their risks and pathogenic mechanisms are crucial for monitoring, prevention, and management of patients' at risk.

Does vigabatrin treatment for infantile spasms cause visual field defects? An international multicentre study

AIM

The aim of this study was to examine whether vigabatrin treatment had caused visual field defects (VFDs) in children of school age who had received the drug in infancy.

METHOD

In total, 35 children (14 males, 21 females; median age 11y, SD 3.4y, range 8-23y) were examined by static Humphrey perimetry, Goldmann kinetic perimetry, or Octopus perimetry. The aetiologies of infantile spasms identified were tuberous sclerosis (n=10), other symptomatic causes (n=3), or cryptogenic (n=22).

RESULTS

Typical vigabatrin-attributed VFDs were found in 11 out of 32 (34%) children: in one out of 11 children (9%) who received vigabatrin for <1 year (group 1), in three out of 10 children (30%) who received vigabatrin for 12 to 24 months (group 2), and in seven out of 11 children (63%) who received vigabatrin treatment for longer than 2 years (group 3). VFDs were mild in five and severe in six children. Patients with tuberous sclerosis were at higher risk of VFDs (six out of 10 children). The mean cumulative doses of vigabatrin were 140.5, 758.8, and 2712g in group 1, 2, and 3, respectively.

INTERPRETATION

VFDs were found in 34% of the cohort of children in this study. The rate of VFD increased from 9% to 63% as duration of treatment increased. The results of this study showed that the risk-benefit ratio should always be considered when using vigabatrin.

Cerebrospinal fluid alterations of the serotonin product, 5-hydroxyindolacetic acid, in neurological disorders

Although patients with low cerebrospinal fluid (CSF) serotonin metabolite levels have been reported, inborn errors of the rate-limiting enzyme of serotonin synthesis (tryptophan hydroxylase, TPH) have not been described so far. In this study we aimed to evaluate CSF alterations of the serotonin metabolite 5-hydroxyindolacetic acid (5-HIAA) in patients with neurological disorders and to explore a possible TPH deficiency in some of them. A total of 606 patients (286 males, 320 females, mean age 4 years and 6 months, SD 5 years and 7 months) underwent CSF analysis of neurotransmitter metabolites by reverse phase high performance liquid chromatography. Results were compared with values established in a control population. Patients' medical records were reviewed to determine diagnosis and clinical features. A primary defect of biogenic amines was genetically investigated in indicated patients. Low 5-HIAA was seen in 19.3%. Of these, 22.2% showed inborn errors of metabolism (mitochondrial disorders being the most frequent at 10.2% of low 5-HIAA patients) and neurogenetic conditions. Other relatively frequent conditions were pontocerebellar hypoplasia (4.3%), Rett syndrome (4.3%), and among congenital nonetiologically determined conditions, epilepsy including epileptic encephalopathies (26.4%), leukodystrophies (6.8%), and neuropsychiatric disturbances (4.2%). Mutational analysis of the TPH2 gene, performed in five candidate patients, was negative. Although frequency of secondary alteration of 5-HIAA was relatively high in patients with neurological disorders, this finding was more frequently associated with some neurometabolic disorders, epileptic encephalopathies, and neuropsychiatric disturbances. No inborn errors of TPH were found. Due to serotonin's neurotrophic role and to ameliorate symptoms, a supplementary treatment with 5-hydroxytriptophan would seem advisable in these patients.

Favourable prognostic factors with infantile spasms

The following aspects are reviewed: Does the aetiology influence the outcome of infantile spasms? Does the treatment influence the outcome? Can the outcome be predicted? Can we improve the prognosis? Favourable factors are the following: cryptogenic aetiology, age at onset > or =4 months, absence of atypical spasms and partial seizures, and absence of asymmetrical EEG abnormalities, short treatment lag, and an early and sustained response to treatment. Not only patients with a cryptogenic aetiology have a favourable outcome. We can already at the first clinical evaluation tell the parents if the prognosis looks favourable. The final goal of the treatment is improved mental outcome. Steroids and vigabatrin are the first-line drugs for infantile spasms in Europe. In a prospective study from the United Kingdom short-term outcome was better with hormonal than with vigabatrin therapy (tuberous sclerosis excluded). However, the numbers of patients who were seizure-free at 3-4 months in different studies have been very similar. Moreover, an early response to treatment seems to be of predictive value for the cognitive outcome in children with cryptogenic spasms. The long-term outcome is known only after hormonal therapy. The side effects of steroids are usually treatable and reversible. In Finland ACTH therapy is given at the minimum effective dose and for the minimum effective time with minimal side effects. The risks of VGB are irreversible visual field defects. As of yet there is no method to examine the visual fields in patients with infantile spasms. Early treatment of infantile spasms seems to be important. Prevention of infantile spasms with some aetiological groups might be possible.

Biochemical diagnosis of dopaminergic disturbances in paediatric patients: analysis of cerebrospinal fluid homovanillic acid and other biogenic amines

Homovanillic acid (HVA) is a major catabolite of dopamine. Its concentration in cerebrospinal fluid (CSF) provides insight into the turnover of dopamine. Our main purpose in this review was to analyze the role played by HVA determination in CSF as a diagnostic and prognostic tool in diseases that directly or indirectly affect the dopaminergic pathway in paediatric patients. There are several rare genetic diseases related with dopamine metabolism disturbances, both in the biosynthesis and catabolism of this neurotransmitter, so that diagnosis is often a major challenge. Decreased concentrations of CSF HVA, together with defects in other biogenic amine metabolites, are the hallmark of dopamine deficiency, and they may provide not only a clue for diagnosis but also information about prognosis and treatment monitoring. Concerning secondary deficiencies, genetic and non-genetic conditions have been identified as the cause of low CSF HVA concentrations, and the variability of clinical presentation and pathophysiological mechanisms is wide. As to CSF HVA analysis, lumbar puncture following a strict protocol has been applied for diagnosis of paediatric neurotransmitter diseases. Among laboratory methods developed for the analysis of CSF HVA and other biogenic amines, high pressure liquid chromatography with electrochemical detection is the most reliable procedure for clinical laboratories. Reference values should be established in each laboratory since there is a strong association between age and biogenic amine concentrations in CSF.

Cerebrospinal fluid pterins and neurotransmitters in early severe epileptic encephalopathies

Early-onset epileptic encephalopathies are devastating conditions. Little is known about pathophysiology and biological markers. We aimed to identify a relationship between the type and prognosis of epileptic encephalopathies starting in infancy and the cerebrospinal fluid profile of pterins and neurotransmitters. Cerebrospinal fluid samples of 23 infants with epileptic encephalopathies were analysed for biogenic amine metabolites (homovanillic and 5-hydroxyindoleacetic acids), and pterins (neopterin and biopterin). West syndrome, early-infantile epileptic encephalopathy with suppression-bursts or Ohtahara syndrome, severe epilepsy with multiple independent spike foci and partial epilepsy with multiple independent spike foci were the four types of epileptic encephalopathy studied. We report clinical, electroencephalographic, neuroimaging and follow-up data. Among the 23 patients studied, 7 had high neopterin levels. Four of them had partial epilepsy with multiple independent spike foci. High neopterin values were associated with mortality (chi square = 7.304, p = 0.007). 5-Hydroxyindoleacetic acid levels were above reference values in three patients, two with partial epilepsy with multiple independent spike foci and one with West syndrome. Homovanillic acid was normal in almost all infants studied. In conclusion, high neopterin levels suggest a cellular immune activation in the central nervous system of these infants, with apparent prognosis implications.

Are early myoclonic encephalopathy (EME) and the Ohtahara syndrome (EIEE) independent of each other?

BACKGROUND

Early myoclonic encephalopathy (EME) and the Ohtahara syndrome are currently listed as two separate syndromes in the classification of epilepsies. The most prominent differentiating points are the observations that patients with Ohtahara syndrome experience predominantly tonic seizures; their seizures evolve to infantile spasms and the prognosis is often worse than patients with EME.

SUMMARY POINTS

We performed a literature review of published cases. Although syndromes may have distinct courses, the differentiation early on may be impossible as both myoclonus and tonic seizures may coexist. There is also an overlap in the etiologies. Tonic seizures are considered a manifestation of brainstem dysfunction and it is possible that this is more prominent in Ohtahara syndrome. To date, there are 17 autopsy cases (12 presumed to be Ohtahara cases and 5 EME). Evidence of hindbrain pathology was present in all. Tonic seizures or tonic posturing was a feature of all cases. We suggest that the two syndromes may represent a continuum and that the prominence of tonic seizures in the Ohtahara syndrome may be an indication of brainstem dysfunction which may play an important role in the subsequent transition to infantile spasms.

Reduced visual function associated with infantile spasms in children on vigabatrin therapy

PURPOSE

To use visual evoked potential (VEP) testing to determine whether visual deficits are present in children with a history of vigabatrin use.

METHODS

Contrast sensitivity and visual acuity were assessed by visual evoked potential testing and compared between 28 children (mean age, 4.90 +/- 4.92 years) with seizure disorders who had taken vigabatrin and 14 typically developing children (mean age, 3.14 +/- 1.70 years). Exclusion criteria were heritable eye disease, suspected cortical visual impairment, nystagmus, and prematurity >2 weeks. The effects of the following factors on contrast sensitivity and visual acuity were examined: type of seizure (infantile spasms versus other), ERG result, duration of vigabatrin therapy, cumulative dosage of vigabatrin, and other seizure medications (other versus no other medication).

RESULTS

Contrast sensitivity and visual acuity were reduced in vigabatrin-treated children with infantile spasms compared with vigabatrin-treated children with other seizure disorders and typically developing control subjects. The other factors examined had no significant effect on contrast sensitivity or visual acuity, with adjustment for seizure type.

CONCLUSIONS

Children with infantile spasms on vigabatrin may have compromised visual function, even in the absence of suspected cortical visual impairment. The children tested in the present study have reduced vision, probably associated with infantile spasms rather than vigabatrin.

Difficulties in establishing reference intervals for special fluids: the example of 5-hydroxyindoleacetic acid and homovanillic acid in cerebrospinal fluids

Biochemical measurements in “special fluids” are complicated with the problem of reference intervals. Reference intervals are difficult to establish for these types of samples since they are usually only collected in patients with clinical suspicion of disease. Determination of neurotransmitter metabolites in cerebrospinal fluid illustrates this difficulty. This paper will review the factors and circumstances that have been identified or are suspected to modifythe concentration of 5-hydroxyindoleacetic acid (5-HIAA) and homovanillic acid (HVA) in cerebrospinal fluid. In addition to obvious parameters such as age-related variation that can affect the concentration of 5-HIAA and HVA in cerebrospinal fluid, a varietyof other factors can explain the wide range of “control” group sizes reported in the literature. Reference intervals must take into account the purpose of cerebrospinal fluid examinations, whether they be prospective studies to explore physio-pathologic relationships or for diagnostic purposes. In the latter case, certain neurological disorders cannot be excluded if a single measured value is within the reference interval.

Role of subcortical structures in the pathogenesis of infantile spasms: what are possible subcortical mediators?

Infantile spasms present a constellation of symptoms and laboratory findings that suggest a role of subcortical circuits in the pathogenesis of this illness. The clinical features of spasms and the influence of subcortical circuits in the regulation of the electroencephologram, along with frequent abnormalities in subcortical structure and functional anatomy, brain stem electrophysiology, sleep regulation, and subcortical neurotransmitter levels, point to the importance of subcortical circuits in the generation of spasms. Furthermore, laboratory evidence shows that modulation of subcortical nuclei may attenuate and ameliorate seizures. We review clinical evidence indicating abnormal function in subcortical circuits and present a hypothesis that the development of infantile spasms requires dysfunction in both cortical and subcortical circuits. The confluence of evidence suggesting a role of subcortical structures in the origin of spasms and laboratory data indicating an anticonvulsant role on some subcortical nuclei raise the possibility of novel approaches to the treatment of infantile spasms.

Prolactin levels in cerebrospinal fluid of patients with infantile spasms

Infantile spasms are an age-related epileptic syndrome of infancy and are characterized by the combination of clusters of epileptic spasms and specific electroencephalographic findings. The etiology and the pathogenesis of the disease is still unclear. Prolactin has been thought to be specifically related to epileptic seizures. To investigate the possible mechanism of prolactin secretion in infantile spasms cerebrospinal fluid prolactin levels were examined. Fifteen patients with infantile spasms (10 females and five males), 3-16 months of age, were evaluated and compared with age- and sex-matched control subject. Cerebrospinal fluid samples for prolactin were obtained before and after treatment. The mean prolactin levels in the cerebrospinal fluid of the patients before therapy (3.25 +/- 1.48 ng/mL) was higher than the control group (2.38 +/- 0.89 ng/mL), and the difference between the two groups was statistically significant (P < 0.001). The mean prolactin level in the cerebrospinal fluid of the patients after therapy (4.69 +/- 1.47 ng/mL) was demonstrated to be higher than the mean prolactin level before therapy (3.25 +/- 1.48 ng/mL) and the difference between the two groups was statistically significant (P = 0.037). Elevation of cerebrospinal fluid prolactin levels before and after treatment in patients with infantile spasms provided evidence that the cerebrospinal fluid prolactin level is related with neuronal injury.

ACTH therapy of West syndrome: Finnish views

To provide up-to-date information on adrenocorticotropic hormone (ACTH) therapy in the treatment of West syndrome, a review of the Finnish studies was made in answer to the questions: what are (1) its efficacy: doses and comparison with vigabatrin (VGB), (2) its tolerability, (3) its mechanism of action? Why do some patients respond, but others do not? No other drugs have been shown to be more effective than ACTH. High doses were not more effective than low doses. Synthetic derivatives were associated with more frequent side effects. Individualized therapy was developed on the basis of etiology and response. With therapy consisting of ACTH 3-6IU/kg/day, all the cryptogenic and half of the symptomatic spasms could be controlled within over 2-3 weeks therapy and with minimal risk of side effects. In a Finnish study, 26% of the patients responded to VGB as the first-line drug. Some of the non-responders responded to ACTH. In tuberous sclerosis, the initial response rate to ACTH was high (73%) and did not differ from the response rate to VGB in other series. Both drugs have severe side effects. The visual field defects caused by VGB occur even in children (in 18/91 Finnish children). The patients with cryptogenic spasms, who responded well to ACTH, differed in their biochemical parameters from the patients with symptomatic spasms. The therapeutic action of ACTH may be mediated by potentiation of nerve growth promoting activity. Neurodegeneration may be due to imbalance between nerve growth factors and nitrate/nitrite in the brain. ACTH should be used as the first choice for treatment of West syndrome (at the minimal effective dose and for shortest effective time). The side effects of steroids, unlike VGB, are well known, treatable, and reversible.

Analysis of CSF amino acids in young patients with generalised refractory epilepsy during an add-on study with lamotrigine

The effect of add-on administration of lamotrigine (1-12 mg/kg per day, 2-12 months) on the levels of neurotransmission related amino acids including gamma-aminobutyric acid (GABA), glutamate, aspartate, glycine and antiepileptic drugs (AEDs) in lumbar cerebrospinal fluid (CSF) was studied in 22 children and young adults with generalised therapy resistant epilepsy. Two lumbar punctures were performed, one prior to, and one following a mean of 5 months (2-12 months) of lamotrigine treatment. Lamotrigine decreased seizure incidence and severity in 12 of the 22 patients without influencing CSF GABA, glutamate, aspartate or glycine levels. Lamotrigine did not alter the concentrations of AEDs in CSF or plasma. However, CSF GABA levels were 86% higher in those patients also treated with gamma-vinyl-GABA (vigabatrin, GVG) compared with patients treated with other combinations and this was not altered by co-medication with lamotrigine. The proposed mechanism of action of lamotrigine, namely that it may inhibit glutamate release in the CNS, is not reflected by changes in CSF glutamate levels. The present findings indicate that CSF GABA, glutamate, aspartate and glycine levels may not be useful as in vivo neurochemical markers in young patients responding to the therapeutic dose of lamotrigine used in this study.

How do cryptogenic and symptomatic infantile spasms differ? Review of biochemical studies in Finnish patients

Infants with cryptogenic infantile spasms seem to differ from those with symptomatic spasms in having a higher cerebrospinal fluid corticotropin content, different levels of corticotropin release after exogenous vasopressin, higher serum levels of progesterone, higher dehydroepiandrosterone: androstenedione ratio (during corticotropin therapy), a higher cerebrospinal fluid gamma-aminobutyric acid content, and higher cerebrospinal fluid nerve growth factor concentrations. It remains to be seen whether the biochemical differences between the two groups are specific or only happen to correlate with the early brain damage. However, these differences would explain many pathophysiologic features of infantile spasms.