Long-Term Follow-up of Patients with Tourette's Syndrome

Background

Tourette's Syndrome (TS) is a childhood-onset movement disorder marked by the chronic presence of motor and vocal tics. Research shows that tics associated with TS tend to fade in severity for some (but not all) affected youth, though psychiatric comorbidities that commonly accompany TS may be more persistent. The long-term outcomes of individuals with TS have not been well characterized.

Objective

To characterize long-term clinical outcomes of individuals with TS.

Method

We conducted a long-term (25-32 years) follow-up study of 45 patients with TS who presented to the Tourette's and Tic Disorders Clinic within the Department of Psychiatry at the University of California San Francisco Medical Center, which was staffed by the first author (Thomas L. Lowe, MD [T.L.L.]), between 1983 and 1990. Baseline data were obtained via chart review, and follow-up data were obtained by self-report surveys.

Results

Participants generally reported good psychosocial functioning, attainment of significant social milestones (academic attainment, gainful employment, marriage), and high subjective quality of life. The vast majority of participants (82%) reported improvement in their tics over time, though a significant minority continued to experience at least mild tic-related impairment (26%-40%, depending on metric). Lifetime rates of attention deficit hyperactivity disorder (ADHD) and anxiety disorders, including obsessive-compulsive disorder, were greater than in the general US population. Robust predictors of follow-up outcomes were not found.

Conclusions

These findings reflect a positive overall long-term prognosis for individuals with TS. Providing information about this prognosis at the time of diagnosis may decrease distress in affected individuals and their families. Future studies using planned longitudinal designs that address potential confounds of survey nonresponse are needed to detail long-term outcomes of individuals with TS more precisely.

Cross-disorder genome-wide analyses suggest a complex genetic relationship between Tourette's syndrome and OCD

OBJECTIVE

Obsessive-compulsive disorder (OCD) and Tourette's syndrome are highly heritable neurodevelopmental disorders that are thought to share genetic risk factors. However, the identification of definitive susceptibility genes for these etiologically complex disorders remains elusive. The authors report a combined genome-wide association study (GWAS) of Tourette's syndrome and OCD.

METHOD

The authors conducted a GWAS in 2,723 cases (1,310 with OCD, 834 with Tourette's syndrome, 579 with OCD plus Tourette's syndrome/chronic tics), 5,667 ancestry-matched controls, and 290 OCD parent-child trios. GWAS summary statistics were examined for enrichment of functional variants associated with gene expression levels in brain regions. Polygenic score analyses were conducted to investigate the genetic architecture within and across the two disorders.

RESULTS

Although no individual single-nucleotide polymorphisms (SNPs) achieved genome-wide significance, the GWAS signals were enriched for SNPs strongly associated with variations in brain gene expression levels (expression quantitative loci, or eQTLs), suggesting the presence of true functional variants that contribute to risk of these disorders. Polygenic score analyses identified a significant polygenic component for OCD (p=2×10(-4)), predicting 3.2% of the phenotypic variance in an independent data set. In contrast, Tourette's syndrome had a smaller, nonsignificant polygenic component, predicting only 0.6% of the phenotypic variance (p=0.06). No significant polygenic signal was detected across the two disorders, although the sample is likely underpowered to detect a modest shared signal. Furthermore, the OCD polygenic signal was significantly attenuated when cases with both OCD and co-occurring Tourette's syndrome/chronic tics were included in the analysis (p=0.01).

CONCLUSIONS

Previous work has shown that Tourette's syndrome and OCD have some degree of shared genetic variation. However, the data from this study suggest that there are also distinct components to the genetic architectures of these two disorders. Furthermore, OCD with co-occurring Tourette's syndrome/chronic tics may have different underlying genetic susceptibility compared with OCD alone.

Copy number variation in obsessive-compulsive disorder and tourette syndrome: a cross-disorder study

OBJECTIVE

Obsessive-compulsive disorder (OCD) and Tourette syndrome (TS) are heritable neurodevelopmental disorders with a partially shared genetic etiology. This study represents the first genome-wide investigation of large (>500 kb), rare (<1%) copy number variants (CNVs) in OCD and the largest genome-wide CNV analysis in TS to date.

METHOD

The primary analyses used a cross-disorder design for 2,699 case patients (1,613 ascertained for OCD, 1,086 ascertained for TS) and 1,789 controls. Parental data facilitated a de novo analysis in 348 OCD trios.

RESULTS

Although no global CNV burden was detected in the cross-disorder analysis or in secondary, disease-specific analyses, there was a 3.3-fold increased burden of large deletions previously associated with other neurodevelopmental disorders (p = .09). Half of these neurodevelopmental deletions were located in a single locus, 16p13.11 (5 case patient deletions: 0 control deletions, p = .08 in the current study, p = .025 compared to published controls). Three 16p13.11 deletions were confirmed de novo, providing further support for the etiological significance of this region. The overall OCD de novo rate was 1.4%, which is intermediate between published rates in controls (0.7%) and in individuals with autism or schizophrenia (2-4%).

CONCLUSION

Several converging lines of evidence implicate 16p13.11 deletions in OCD, with weaker evidence for a role in TS. The trend toward increased overall neurodevelopmental CNV burden in TS and OCD suggests that deletions previously associated with other neurodevelopmental disorders may also contribute to these phenotypes.

Partitioning the heritability of Tourette syndrome and obsessive compulsive disorder reveals differences in genetic architecture

The direct estimation of heritability from genome-wide common variant data as implemented in the program Genome-wide Complex Trait Analysis (GCTA) has provided a means to quantify heritability attributable to all interrogated variants. We have quantified the variance in liability to disease explained by all SNPs for two phenotypically-related neurobehavioral disorders, obsessive-compulsive disorder (OCD) and Tourette Syndrome (TS), using GCTA. Our analysis yielded a heritability point estimate of 0.58 (se = 0.09, p = 5.64e-12) for TS, and 0.37 (se = 0.07, p = 1.5e-07) for OCD. In addition, we conducted multiple genomic partitioning analyses to identify genomic elements that concentrate this heritability. We examined genomic architectures of TS and OCD by chromosome, MAF bin, and functional annotations. In addition, we assessed heritability for early onset and adult onset OCD. Among other notable results, we found that SNPs with a minor allele frequency of less than 5% accounted for 21% of the TS heritability and 0% of the OCD heritability. Additionally, we identified a significant contribution to TS and OCD heritability by variants significantly associated with gene expression in two regions of the brain (parietal cortex and cerebellum) for which we had available expression quantitative trait loci (eQTLs). Finally we analyzed the genetic correlation between TS and OCD, revealing a genetic correlation of 0.41 (se = 0.15, p = 0.002). These results are very close to previous heritability estimates for TS and OCD based on twin and family studies, suggesting that very little, if any, heritability is truly missing (i.e., unassayed) from TS and OCD GWAS studies of common variation. The results also indicate that there is some genetic overlap between these two phenotypically-related neuropsychiatric disorders, but suggest that the two disorders have distinct genetic architectures.

CNV analysis in Tourette syndrome implicates large genomic rearrangements in COL8A1 and NRXN1

Tourette syndrome (TS) is a neuropsychiatric disorder with a strong genetic component. However, the genetic architecture of TS remains uncertain. Copy number variation (CNV) has been shown to contribute to the genetic make-up of several neurodevelopmental conditions, including schizophrenia and autism. Here we describe CNV calls using SNP chip genotype data from an initial sample of 210 TS cases and 285 controls ascertained in two Latin American populations. After extensive quality control, we found that cases (N = 179) have a significant excess (P = 0.006) of large CNV (>500 kb) calls compared to controls (N = 234). Amongst 24 large CNVs seen only in the cases, we observed four duplications of the COL8A1 gene region. We also found two cases with ∼400 kb deletions involving NRXN1, a gene previously implicated in neurodevelopmental disorders, including TS. Follow-up using multiplex ligation-dependent probe amplification (and including 53 more TS cases) validated the CNV calls and identified additional patients with rearrangements in COL8A1 and NRXN1, but none in controls. Examination of available parents indicates that two out of three NRXN1 deletions detected in the TS cases are de-novo mutations. Our results are consistent with the proposal that rare CNVs play a role in TS aetiology and suggest a possible role for rearrangements in the COL8A1 and NRXN1 gene regions.

Prevalence and clinical correlates of explosive outbursts in Tourette syndrome

The aim of this study was to examine the prevalence and clinical correlates of explosive outbursts in two large samples of individuals with Tourette syndrome (TS), including one collected primarily from non-clinical sources. Participants included 218 TS-affected individuals who were part of a genetic study (N=104 from Costa Rica (CR) and N=114 from the US). The relationships between explosive outbursts and comorbid attention deficit hyperactivity disorder (ADHD), obsessive-compulsive disorder (OCD), tic severity, and prenatal and perinatal complications were examined using regression analyses. Twenty percent of participants had explosive outbursts, with no significant differences in prevalence between the CR (non-clinical) and the US (primarily clinical) samples. In the overall sample, ADHD, greater tic severity, and lower age of tic onset were strongly associated with explosive outbursts. ADHD, prenatal exposure to tobacco, and male gender were significantly associated with explosive outbursts in the US sample. Lower age of onset and greater severity of tics were significantly associated with explosive outbursts in the CR sample. This study confirms previous studies that suggest that clinically significant explosive outbursts are common in TS and associated with ADHD and tic severity. An additional potential risk factor, prenatal exposure to tobacco, was also identified.

Tic symptom profiles in subjects with Tourette Syndrome from two genetically isolated populations

BACKGROUND

Tourette Syndrome (TS) has a complex etiology and wide variability in phenotypic expression. Identifying underlying symptom patterns may be useful for etiological and outcome studies of TS.

METHODS

Lifetime tic and related symptom data were collected between 1996 and 2001 in 121 TS subjects from the Central Valley of Costa Rica and 133 TS subjects from the Ashkenazi Jewish (AS) population in the US. Subjects were grouped by tic symptoms using an agglomerative hierarchical cluster analysis. Cluster membership was tested for association with available ancillary information (age of onset, tic severity, comorbid disorders, medication treatment and family history).

RESULTS

Cluster analysis identified two distinct groups in each sample, those with predominantly simple tics (cluster 1), and those with multiple complex tics (cluster 2). Membership in cluster 2 was correlated with increased tic severity, global impairment, medication treatment, and presence of comorbid obsessive-compulsive symptoms in both samples, and with family history of tics, lower verbal IQ, earlier age of onset, and comorbid obsessive-compulsive disorder and attention-deficit/hyperactivity disorder in the AS sample.

CONCLUSIONS

This study provides evidence for consistent and reproducible symptom profiles in two independent TS study samples. These findings have implications for etiological studies of TS.

Overrepresentation of rare variants in a specific ethnic group may confuse interpretation of association analyses

Rare sequence variants may be important in understanding the biology of common diseases, but clearly establishing their association with disease is often difficult. Association studies of such variants are becoming increasingly common as large-scale sequence analysis of candidate genes has become feasible. A recent report suggested SLITRK1 (Slit and Trk-like 1) as a candidate gene for Tourette Syndrome (TS). The statistical evidence for this suggestion came from association analyses of a rare 3'-UTR variant, var321, which was observed in two patients but not observed in more than 2000 controls. We genotyped 307 Costa Rican and 515 Ashkenazi individuals (TS probands and their parents) and observed var321 in five independent Ashkenazi parents, two of whom did not transmit this variant to their affected child. Furthermore, we identified var321 in one subject from an Ashkenazi control sample. Our findings do not support the previously reported association and suggest that var321 is overrepresented among Ashkenazi Jews compared with other populations of European origin. The results further suggest that overrepresentation of rare variants in a specific ethnic group may complicate the interpretation of association analyses of such variants, highlighting the particular importance of precisely matching case and control populations for association analyses of rare variants.

Association between maternal smoking and increased symptom severity in Tourette's syndrome

OBJECTIVE

Substantial evidence suggests that both environmental and genetic factors contribute to the development and clinical expression of Tourette's syndrome. Although genetic studies of Tourette's syndrome are common, studies of environmental factors are relatively few and have not identified consistent risk factors across studies. This study examines in a large cohort of subjects (N=180) the relationship between prenatal/perinatal adverse events with Tourette's syndrome severity as determined by tic severity and rates of commonly comorbid disorders such as obsessive-compulsive disorder (OCD), attention deficit hyperactivity disorder (ADHD), and self-injurious behavior.

METHOD

Tic severity, OCD, ADHD, self-injurious behavior, and exposure to a variety of prenatal/perinatal events were systematically assessed in all subjects enrolled in three genetic studies of Tourette's syndrome. Using linear and logistic regression, a best-fit model was determined for each outcome of interest.

RESULTS

Prenatal maternal smoking was strongly correlated with increased tic severity and with the presence of comorbid OCD in these Tourette's syndrome subjects. Other variables, such as paternal age and subject's birth weight, were significantly but less strongly associated with increased symptom severity. The authors found no association between symptom severity and hypoxia, forceps delivery, or hyperemesis during pregnancy, which have been previously identified as risk factors.

CONCLUSIONS

This study identifies prenatal maternal smoking as a strong risk factor for increased symptom severity in Tourette's syndrome.

Genetic studies of neuropsychiatric disorders in Costa Rica: a model for the use of isolated populations

The importance of genetics in understanding the etiology of mental illness has become increasingly clear in recent years, as more evidence has mounted that almost all neuropsychiatric disorders have a genetic component. It has also become clear, however, that these disorders are etiologically complex, and multiple genetic and environmental factors contribute to their makeup. So far, traditional linkage mapping studies have not definitively identified specific disease genes for neuropsychiatric disorders, although some potential candidates have been identified via these methods (e.g. the dysbindin gene in schizophrenia; Straub et al., 2002; Schwab et al., 2003). For this reason, alternative approaches are being attempted, including studies in genetically isolated populations. Because isolated populations have a high degree of genetic homogeneity, their use may simplify the process of identifying disease genes in disorders where multiple genes may play a role. Several areas of Latin America contain genetically isolated populations that are well suited for the study of neuropsychiatric disorders. Genetic studies of several major psychiatric illnesses, including bipolar disorder, major depression, schizophrenia, Tourette Syndrome, alcohol dependence, attention deficit hyperactivity disorder, and obsessive-compulsive disorder, are currently underway in these regions. In this paper we highlight the studies currently being conducted by our groups in the Central Valley of Costa Rica to illustrate the potential advantages of this population for genetic studies.

Self injurious behaviour in Tourette syndrome: correlates with impulsivity and impulse control

BACKGROUND

Self injurious behaviour (SIB), the deliberate, repetitive infliction of self harm, is present in a wide variety of neuropsychiatric disorders, including Tourette syndrome (TS). Although SIB occurs in up to 60% of individuals with TS, and can cause significant clinical impairment and distress, little is known about its aetiology.

OBJECTIVE

This study examined the relationship between SIB and other behavioural features that commonly co-occur with TS in nearly 300 subjects with TS participating in three genetic studies. SIB, obsessions, compulsions, tic severity, attention deficit hyperactivity disorder related impulsivity, risk taking behaviours, and rages were systematically assessed in all subjects.

METHODS

Using logistic regression, a best fit model was determined for both mild to moderate SIB and severe SIB.

RESULTS

Mild/moderate SIB in TS was correlated with the presence of obsessive and compulsive symptoms such as the presence of aggressive obsessions or violent or aggressive compulsions, and with the presence of obsessive-compulsive disorder and overall number of obsessions. Severe SIB in TS was correlated with variables related to affect or impulse dysregulation; in particular, with the presence of episodic rages and risk taking behaviours. Both mild/moderate and severe SIB were also correlated with tic severity.

CONCLUSIONS

This study suggests that mild/moderate and severe SIB in TS may represent different phenomena, which has implications for clinical management of these symptoms.

Structure-function relationships for inhibitors of beta-amyloid toxicity containing the recognition sequence KLVFF

Beta-amyloid (Abeta), the primary protein component of Alzheimer's plaques, is neurotoxic when aggregated into fibrils. We have devised a modular strategy for generating compounds that inhibit Abeta toxicity. These compounds contain a recognition element, designed to bind to Abeta, linked to a disrupting element, designed to interfere with Abeta aggregation. On the basis of this strategy, a hybrid peptide was synthesized with the sequence KLVFF (residues 16-20 of Abeta) as the recognition element and a lysine hexamer as the disrupting element; this compound protects cells in vitro from Abeta toxicity [Pallitto, M. M., et al. (1999) Biochemistry 38, 3570]. To determine if the length of the disrupting element could be reduced, peptides were synthesized that contained the KLVFF recognition element and a sequence of one to six lysines as disrupting elements. All compounds enhanced the rate of aggregation of Abeta, with the magnitude of the effect increasing as the number of lysines in the disrupting element increased. The greatest level of protection against Abeta toxicity was achieved with compounds containing disrupting elements of three or more lysines in sequence. A peptide with an anionic disrupting element, KLVFFEEEE, had activity similar to that of KLVFFKKKK, in both cellular toxicity and biophysical assays, whereas a peptide with a neutral polar disrupting element, KLVFFSSSS, was ineffective. Protective compounds retained activity even at an inhibitor:Abeta molar ratio of 1:100, making these some of the most effective inhibitors of Abeta toxicity reported to date. These results provide critical insight needed to design more potent inhibitors of Abeta toxicity and to elucidate their mechanism of action.

Cultural influences on diagnosis and perception of Tourette syndrome in Costa Rica

BACKGROUND AND OBJECTIVES

Tourette syndrome (TS) is a neuropsychiatric disorder in which the pattern of symptom presentation can vary greatly between individuals. Although globally described, TS has not been well characterized in many parts of the world. Differences in individual and cultural perceptions of TS may impact its expression and recognition in some countries, confounding the identification of affected individuals. This study examines the phenomenology and presentation of TS in Costa Rica.

METHOD

Clinical data on 85 Costa Rican subjects with TS (aged 5-29 years) initially recruited for a genetic study between 1996 and early 2000 were obtained by direct interview and review of medical records.

RESULTS

The clinical characteristics of TS were similar to that found elsewhere. The gender ratio was 4.6:1, the mean age of onset was 6.1 years, and 20% of subjects had coprolalia. However, the perceived impact of TS was different. Many subjects denied that their TS caused impairment or distress, even when objective evidence of impairment was available.

CONCLUSIONS

TS in Costa Rica is phenomenologically similar to TS seen in other parts of the world, but differs in perceived impairment. In other countries where cultural forces affect disease definition, close scrutiny of symptom expression and possible adjustment of phenotype definition may be important.

Depressed mood during pregnancy and the puerperium: clinical recognition and implications for clinical practice

Mild to moderate depression is common among women during the first 3 months postpartum. The authors studied 20 normal pregnant women in the hope of finding valid predictors of postpartum mood disorder. The subjects rated their level of emotions and various depressive symptoms at 26 and 36 weeks of pregnancy and filled out a brief questionnaire about the emotional circumstances of their pregnancy. The mood scales were repeated at 2 days and 6 weeks postpartum, along with a clinical interview. The antepartum mood scale identified women with postpartum depression and differentiated this condition from the more common, transient postpartum blues. Certain psychosocial variables also predicted postpartum distress. The authors discuss the implications of these findings, emphasizing the feasibility and necessity of routine screening for mood disturbances in prenatal and puerperal women.

Stimulant medications precipitate Tourette's syndrome

Following treatment with stimulant medications for symptoms of attention deficit disorder, Gilles de la Tourette's syndrome occurred in 15 patients. Early signs of Tourette's syndrome may be difficult to distinguish from hyperactive and attention disordered symptoms, leading the clinician to consider treatment with stimulants. In these Tourette's-susceptible patients, stimulants may exacerbate severe motor and phonic tics, requiring discontinuation of administration of stimulants and institution of haloperidol therapy for tic control. Clinical evaluation for tics and Tourette's syndrome in children and their families should precede and dictate use of stimulant medications in children.

Stimulant medications precipitate Tourette's syndrome

Following treatment with stimulant medications for symptoms of attention deficit disorder, Gilles de la Tourette's syndrome occurred in 15 patients. Early signs of Tourette's syndrome may be difficult to distinguish from hyperactive and attention disordered symptoms, leading the clinician to consider, treatment with stimulants. In these Tourette's-susceptible patients, stimulants may exacerbate severe motor and phonic tics, requiring discontinuation of administration of stimulants and institution of haloperidol therapy for tic control. Clinical evaluation for tics and Tourette's syndrome in children and their families should precede and dictate use of stimulant medications in children.

Thyroid hormone in autistic children

Thyroid hormone plays an important role in the pre- and postnatal development and function of the central nervous system. Disturbances in thyroid hormone regulation have been hypothesized in childhood autism. We evaluated blood indices of thyroid function, including serum thyroxine, triiodothyronine, and thyroid-stimulating hormone, in a large population of autistic children. No differences were found between autistic and normal children.

Detection of phenylketonuria in autistic and psychotic children

Sixty-five children with pervasive developmental disturbance (autism and atypical childhood psychosis) were screened by standard urinary amino acid detection testing methods. Three of the children showed abnormalities in these screening tests, leading to the diagnosis of phenylketonuria. This was verified by repeated urinary testing and blood phenylalanine determinations. The children with phenylketonuria were treated with low-phenylalanine diets and have shown improvement in functioning and developmental level since treatment. Urinary genetic screening should be a standard test for all children being evaluated for serious developmental disturbances of childhood.

Quantitation of Neisseria gonorrhoeae from women with gonorrhea

The number of infecting organisms has been shown to be an important variable in animal models of infection with Neisseria gonorrhoeae. This variable may also be important in the natural transmission of gonorrhea in humans. The number of gonococci in the cervicovaginal area of women with gonorrhea is unknown, as are the effects of certain physiologic or therapeutic variables on the number of gonococci. In this study a semiquantitative technique for the enumeration of N. gonorrhoeae was used; 10 ml of phosphate-buffered saline was directed against the cervix and vaginal wall, and the number of colony-forming units (cfu) of N. gonorrhoeae in the aspirate was determined. The number of N. gonorrhoeae recovered ranged from 4.0 X 10(2) to 1.8 X 10(7) cfu. The geometric mean number was 1.45 X 10(5) cfu, with a standard deviation of 1.04 X 10(1) cfu. Statistical analyses showed that the number of gonococci was not influenced by the use of oral contraceptives, concurrent infection with Trichomonas vaginalis and/or Corynebacterium (Haemophilus)vaginalis, time of douche prior to examination, or phase of the menstrual cycle at which the women were examined. The results indicated a wide range in the number of N. gonorrhoeae recoverable by vaginal irrigation but failed to define the reason for this variability.