ADHD and epilepsy in children with Tourette syndrome: a triple comorbidity?

Improvement of Tourette syndrome symptoms after intractable temporal lobe epileptic surgery: a case report

BACKGROUND

The comorbidities of either epilepsy or Tourette syndrome (TS) are heterogeneous. However, the co-occurrence of epilepsy and TS conditions is rarely encountered, let alone effective treatments that address both neurologic disorders at the same time.

METHODS

We report a 24-year-old female patient who was diagnosed with TLE and TS. She presented for seizure control. After evaluation with stereo-electroencephalography and electrocorticography monitoring, the patient underwent a resective surgery treatment and was followed for 9 months.

RESULTS

At the last follow-up, the patient remained seizure free and unexpectedly showed great improvement in TS symptoms and its psychiatric comorbidities.

CONCLUSION

This anecdotal case highlights the close association between TLE and TS and we suggest that epilepsy and TS share some common pathophysiologic mechanisms.

Copy Number Variations in Children with Tourette Syndrome: Systematic Investigation in a Clinical Setting

Tourette syndrome (TS) is a neurodevelopmental disturbance with heterogeneous and not completely known etiology. Clinical and molecular appraisal of affected patients is mandatory for outcome amelioration. The current study aimed to understand the molecular bases underpinning TS in a vast cohort of pediatric patients with TS. Molecular analyses included array-CGH analyses. The primary goal was to define the neurobehavioral phenotype of patients with or without pathogenic copy number variations (CNVs). Moreover, we compared the CNVs with CNVs described in the literature in neuropsychiatric disorders, including TS, to describe an effective clinical and molecular characterization of patients for prognostic purposes and for correctly taking charge. Moreover, this study showed that rare deletions and duplications focusing attention on significant genes for neurodevelopment had a statistically higher occurrence in children with tics and additional comorbidities. In our cohort, we determined an incidence of potentially causative CNVs of about 12%, in line with other literature studies. Clearly, further studies are needed to delineate the genetic background of patients with tic disorders in a superior way to elucidate the complex genetic architecture of these disorders, to describe the outcome, and to identify new possible therapeutic targets.

Attention-deficit/hyperactive disorder updates

Background

Attention-deficit/hyperactive disorder (ADHD) is a neurodevelopmental disorder that commonly occurs in children with a prevalence ranging from 3.4 to 7.2%. It profoundly affects academic achievement, well-being, and social interactions. As a result, this disorder is of high cost to both individuals and society. Despite the availability of knowledge regarding the mechanisms of ADHD, the pathogenesis is not clear, hence, the existence of many challenges especially in making correct early diagnosis and provision of accurate management.

Objectives

We aimed to review the pathogenic pathways of ADHD in children. The major focus was to provide an update on the reported etiologies in humans, animal models, modulators, therapies, mechanisms, epigenetic changes, and the interaction between genetic and environmental factors.

Methods

References for this review were identified through a systematic search in PubMed by using special keywords for all years until January 2022.

Results

Several genes have been reported to associate with ADHD: DRD1, DRD2, DRD4, DAT1, TPH2, HTR1A, HTR1B, SLC6A4, HTR2A, DBH, NET1, ADRA2A, ADRA2C, CHRNA4, CHRNA7, GAD1, GRM1, GRM5, GRM7, GRM8, TARBP1, ADGRL3, FGF1, MAOA, BDNF, SNAP25, STX1A, ATXN7, and SORCS2. Some of these genes have evidence both from human beings and animal models, while others have evidence in either humans or animal models only. Notably, most of these animal models are knockout and do not generate the genetic alteration of the patients. Besides, some of the gene polymorphisms reported differ according to the ethnic groups. The majority of the available animal models are related to the dopaminergic pathway. Epigenetic changes including SUMOylation, methylation, and acetylation have been reported in genes related to the dopaminergic pathway.

Conclusion

The dopaminergic pathway remains to be crucial in the pathogenesis of ADHD. It can be affected by environmental factors and other pathways. Nevertheless, it is still unclear how environmental factors relate to all neurotransmitter pathways; thus, more studies are needed. Although several genes have been related to ADHD, there are few animal model studies on the majority of the genes, and they do not generate the genetic alteration of the patients. More animal models and epigenetic studies are required.

Potential for diagnosis versus therapy monitoring of attention deficit hyperactivity disorder: a new epigenetic biomarker interacting with both genotype and auto-immunity

In view of the need for easily accessible biomarkers, we evaluated in ADHD children the epigenetic status of the 5'-untranslated region (UTR) in the SLC6A3 gene, coding for human dopamine transporter (DAT). We analysed buccal swabs and sera from 30 children who met DSM-IV-TR criteria for ADHD, assigned to treatment according to severity. Methylation levels at six-selected CpG sites (among which, a CGGCGGCGG and a CGCG motif), alone or in combination with serum titers in auto-antibodies against dopamine transporter (DAT aAbs), were analysed for correlation with CGAS scores (by clinicians) and Conners' scales (by parents), collected at recruitment and after 6 weeks. In addition, we characterized the DAT genotype, i.e., the variable number tandem repeat (VNTR) polymorphisms at the 3'-UTR of the gene. DAT methylation levels were greatly reduced in ADHD patients compared to control, healthy children. Within patients carrying at least one DAT 9 allele (DAT 9/x), methylation at positions CpG2 and/or CpG6 correlated with recovery, as evident from delta-CGAS scores as well as delta Conners' scales ('inattentive' and 'hyperactive' subscales). Moreover, hypermethylation at CpG1 position denoted severity, specifically for those patients carrying a DAT 10/10 genotype. Intriguingly, high serum DAT-aAbs titers appeared to corroborate indications from high CpG1 versus high CpG2/CpG6 levels, likewise denoting severity versus recovery in DAT 10/10 versus 9/x patients, respectively. These profiles suggest that DAT 5'UTR epigenetics plus serum aAbs can serve as suitable biomarkers, to confirm ADHD diagnosis and/or to predict the efficacy of treatment.

Increased risks of tic disorders in children with epilepsy: A nation-wide population-based case-control study in Taiwan

Both epilepsy and tic disorders may share common mechanisms with the involvement of abnormal cortical-basal ganglion circuit connection and dopaminergic dysfunction. However, the association between epilepsy and tic disorders has never been studied. This study investigated the risks of developing tic disorders among children with epilepsy using databases of a universal health insurance system in Taiwan. The data analyzed in this study were retrieved from the National Health Insurance Research Database in Taiwan. The study cohort included children with epilepsy between 2001 and 2007 (n=2629) and a three-fold age- and gender-matched controls (n=7887). All subjects were followed up for 3 years from the date of cohort entry to identify their admissions due to tic disorders (ICD-9-CM codes 307.2, 307.20-307.23). Cox hazard regression analysis was performed to estimate the effect of epilepsy on the occurrence of tics. The epilepsy cohort had a higher prevalence of tics (1.7% vs. 0.2%), and a 8.70-fold increased risk of developing a tic disorder compared with the controls (adjusted hazard ratio (AHR) 8.70, 95% confidence interval (CI) 4.26-16.37, p<0.001). Male patients were observed to have a higher risk of developing a tic disorder (AHR 1.90, 95% CI=1.04-3.46, p<0.001) compared to female individuals. Patients with multiple antiepileptic drugs treatment also exhibited higher crude OR for developing tic disorders. This nationwide population-based cohort study, for the first time, demonstrated that there is a significantly increased risk for tic disorders among children with epilepsy. We also found males, attention deficit disorder and the use of multiple AEDs to be independent risk factors of tic disorders. Closely evaluating possible tic disorders would be crucial for improving the outcome and life quality in children with epilepsy.

Increased risk of epilepsy in children with Tourette syndrome: A population-based case-control study

The association between epilepsy and Tourette syndrome has rarely been investigated. In this retrospective cohort study, we analyzed a dataset of 1,000,000 randomly sampled individuals from the Taiwan National Health Insurance Research Database to determine the risk of epilepsy in children with Tourette syndrome. The study cohort consisted of 1062 patients with Tourette syndrome aged ≤ 18 years, and the control group consisted of three times the number of age- and sex-matched patients without Tourette syndrome, who were insurants, from the same database during the same period. The Tourette syndrome group had an 18.38-fold increased risk of epilepsy than the control group [hazard ratio=18.38, 95% confidence interval (CI)=8.26-40.92; P<0.001]. Even after adjusting for the comorbidities, the risk of epilepsy in the Tourette syndrome group with comorbidities remained high (hazard ratio=16.27, 95% CI=6.26-18.46; P<0.001), indicating that the increased risk was not associated with comorbidities. This population-based retrospective cohort study provides the first and strong evidence that Tourette syndrome is associated with a higher risk of epilepsy. A close follow-up of children with Tourette syndrome for the development of epilepsy is warranted.

Detection of auto-antibodies to DAT in the serum: interactions with DAT genotype and psycho-stimulant therapy for ADHD

Interest is rising for auto-immune contribution in neuro-psychiatry. We evaluated the auto-antibodies against dopamine transporter (DAT aAbs) in 61 children (46 ADHD who met DSM-IV-TR criteria, 15 healthy controls).

METHODS

ADHD patients were assigned, according to severity, either to a non-pharmacological therapy (NPT, N=32) or to a pharmacological treatment (PT, N=14) with methylphenidate (MPH). In ADHD children, blood samples were withdrawn twice, at recruitment (T0 basal) and after 6 weeks (T1); following 16 excluded subjects, DAT genotype was characterized (9-repeat or 10-repeat alleles; N=15 each). After 18 months of NPT or PT, some patients (carrying at least one 9-repeat allele) were blood sampled again (T2), for comparison with healthy controls (final n=8) RESULTS: Compared to NPT, basal DAT aAbs titers were higher within most severe patients (then assigned to PT), specifically if carrying a DAT 10/10 genotype. DAT aAbs levels of NPT group resulted highly correlated with distinct subscales of Conners' Parent/Teacher Scales (Rs>0.34), especially within DAT 10/10 genotype (Rs>0.53). While T1 titers were elevated over T0 baseline for NPT children, such an increase was not observed in PT patients carrying at least one 9-repeat allele, who also showed behavioral response to subchronic MPH. After 12-24 months of MPH exposure, DAT aAbs titers in PT subjects were comparable to those of healthy controls, while titers remained significantly elevated in NPT patients. Data warrant further research on serum DAT aAbs, which could be used to confirm ADHD diagnosis and/or to monitor therapeutic efficacy of MPH.

Tourette Syndrome and comorbid ADHD: current pharmacological treatment options

BACKGROUND

Attention Deficit Hyperactivity Disorder (ADHD) is the most common co-morbid condition encountered in people with tics and Tourette Syndrome (TS). The co-occurrence of TS and ADHD is associated with a higher psychopathological, social and academic impairment and the management may represent a challenge for the clinicians.

AIM

To review recent advances in management of patients with tic, Tourette Syndrome and comorbid Attention Deficit Hyperactivity Disorder.

METHODS

We searched peer reviewed and original medical publications (PUBMED 1990-2012) and included randomized, double-blind, controlled trials related to pharmacological treatment for tic and TS used in children and adolescents with comorbid ADHD. "Tourette Syndrome" or "Tic" and "ADHD", were cross referenced with the words "pharmacological treatment", "α-agonist", "psychostimulants", "selective norepinephrine reuptake inhibitor", "antipsychotics".

RESULTS

Three classes of drugs are currently used in the treatment of TS and comorbid ADHD: α-agonists (clonidine and guanfacine), stimulants (amphetamine enantiomers, methylphenidate enantiomers or slow release preparation), and selective norepinephrine reuptake inhibitor (atomoxetine). It has been recently suggested that in a few selected cases partial dopamine agonists (aripiprazole) could be useful.

CONCLUSION

Level A of evidence supported the use of noradrenergic agents (clonidine). Reuptake inhibitors (atomoxetine) and stimulants (methylphenidate) could be, also used for the treatment of TS and comorbid ADHD. Taking into account the risk-benefit profile, clonidine could be used as the first line treatment. However only few studies meet rigorous quality criteria in terms of study design and methodology; most trials have low statistical power due to small sample size or short duration. Treatment should be "symptom targeted" and personalized for each patient.