How Much Do We Know about Adult-onset Primary Tics? Prevalence, Epidemiology, and Clinical Features

Introduction

Tics are brief, intermittent, sudden movements or sounds that occur in a stereotyped fashion. Diagnostic classification systems require the onset of tics prior to the age of either 18^1,2 or 21³ years for the diagnosis of Tourette syndrome (TS), persistent tic disorder, or provisional disorder.¹ This upper age limit is somewhat arbitrary and has varied from one classification to the next,⁴ as tics presenting after 21 have been long recognized. Tic disorders arising in adulthood are therefore categorized as “Tic disorder not otherwise specified”¹ or “Tic disorder, unspecified”.² By some estimates, tics that are due to a secondary cause such as drug use, brain insult or neurodegenerative disease constitute approximately one-half or one-third of adults with new-onset underlying tics.^5,6 The newest edition of the Diagnostic and statistical manual of mental disorders has added secondary and drug-induced tics as diagnostic categories in recognition of the significant number of patients described in the literature with secondary tics. There are a handful of reviews and larger clinical studies focusing on secondary tics.^7,8 Adults feature prominently in these descriptions, since they are more likely to have acquired neurologic disorders, experienced trauma, or been exposed to neuroleptics. The topic of adult-onset, primary tics however has garnered little attention in the literature. This review seeks to summarize our current understanding of adult-onset, primary tic disorders in terms of their epidemiology and clinical features. The differentiation of primary from secondary tics is given some attention.

Methods

The goal of the search was to be as comprehensive as possible in locating studies and reviews of research on any aspect of adult-onset tics. The following databases were searched on October 2016 without any time period limitations: PubMed, SCOPUS, and Web of Science using variations of the terms adult- and late-onset tics (“adult onset tics”, “adult onset” and tics, late onset tics, “adult tic disorders” and tics and late onset”). This resulted in 60 articles in PubMed, 64 articles in SCOPUS, and 73 articles in Web of Science, totaling 227 articles, or a pool of 120 unique articles. Duplicates were removed and the remainder were reviewed to make sure they were indeed relevant to the subject. Next the references and citing references were reviewed for each of the articles. Google Scholar was also used to help in finding citing references. Finally a total of 52 papers were found to be relevant and have been included in this review. No previous review paper was found.

Primary vs. secondary tics

The distinction between primary and secondary tics has been made in the literature; however, there is considerable overlap between the two groups. Primary tics are idiopathic tics that may share a common pathophysiology with childhood-onset tic disorders and TS. Secondary tics result from or are associated with another medical condition. In many cases, the causal relationship between the associated condition and the tics themselves has been adequately demonstrated either through a repeated association or through the recognition that common neurobiologic pathways are at play, such as those affecting the basal ganglia.^7,9,10 However, not all authors differentiate between causation and association,⁸ which creates confusion surrounding proper categorization.

The second issue that leads to overlap between these groups arises because TS is a complex, highly heritable disorder resulting from a poorly understood interplay between genetics and environment.¹¹ Over 85% of patients with TS suffer from one other psychiatric disorder, the most common being ADHD (attention deficit hyperactivity disorder), followed by OCD (obsessive compulsive disorder),¹² and almost 30% of patients with OCD suffer from tics; this suggests a role for shared genes in these conditions.¹³ Some individuals with a psychiatric comorbidity may therefore demonstrate a tic diathesis without manifesting tics, and they may be predisposed to developing tics in the setting of a particular event or illness. In children, physical and psychosocial stress, fatigue, pre- and perinatal adverse events, and Group A streptococcal infections have been linked to tics and to worsening of tics and related symptoms.^14,15 Biochemically, the relationship between psychosocial stress and tic disorders may be related to aberrations in the hypothalamic–pituitary–adrenal axis and its associated hormones and neurotransmitters that are critical to the stress response.^16,17 A triggering event such as physical trauma, a new medication, or the onset of a neurologic disorder could provoke tics in a predisposed individual who might otherwise never have developed tics. In such cases then the difference between primary and secondary tics becomes blurred, since the triggering event would not have resulted in tics in the absence of a genetic susceptibility to developing tics.

Adult-onset or childhood recurrence?

Often, primary adult-onset tics actually represent a recurrence of unrecognized childhood tics.⁵ While TS has been recognized since its original description in the 1890s as a lifelong disorder,¹⁸ the condition generally improves in early adulthood.¹⁹ Tics also tend to wax and wane over time.²⁰ Patients may therefore present as adults to medical providers during a period of tics recurrence, often to adult neurologists rather than the pediatric psychiatrists seen in childhood. These patients may be unaware that they suffered from tics as children,^6,21 or be unable to recall their own remote history especially if they were very young when tics were present. The largest study dedicated to adult-onset tic disorders identified 22 patients who presented for the first time to a movement disorders clinic with tic disorders;⁵ of these, nine patients (41%) were found to have a history of childhood transient tic disorder after detailed questioning. Of these nine patients, six were between the ages of 25 and 41 years at the time of recurrence, and three were in their early sixties. Tics may therefore recur in a patient with childhood tics 40 years or more after tics remitted.^22–24 Sadnyk and Awerbuch²³ present a woman who experienced recurrence of her motor and vocal tic disorder at the age of 73, and was successfully treated with opiates. Klawans and Barr²² present four patients, all of whom suffered from childhood tics that remitted by the age of 20 but recurred at the ages of 62, 63, 65, and 71. Tics were phenomenologically similar to those occurring in childhood, suggesting that these were indeed recurrences of previous tics rather than a new tic disorder. Based on the paucity of cases in the literature, recurrence of tics in late adulthood seems to be a rare occurrence. However, reported cases likely represent an underestimation of the true prevalence, as the proper identification of cases requires detailed questioning of both the patient and the family members.

Primary tics

Descriptions of adult-onset tics not attributed to any other neurologic disorder and not because of recurrence of childhood tics are few; these are presented in Table 1. Only three case series^4,5,25 and five case reports^26–30 are devoted to this topic. A study on the clinical characteristics of tics in adults with TS identified eight (of 46) patients who developed tics after the age of 18, but no individual data were presented on these cases.³¹ A number of cases that have been previously classified as adult-onset primary tics either by the author or citing authors, were not included either because there was insufficient information to determine whether they truly represented idiopathic tics,³² or because a secondary cause seemed more likely.^24,33 Eapen et al. discuss eight patients who developed tics at ages 23–50 and who are presented as having idiopathic tics.⁴ In all eight cases there was a potential triggering event for the tics; however, in five cases this event was more likely to play a causative role. In these five cases, one patient had prior exposure to a neuroleptic, three had preceding infections, and one suffered a motor vehicle accident, all of which have been associated with the development of tics.^8,34–37 In the remaining three cases in the series, one patient’s tics were preceded by exposure to benzodiazepine and alcohol, one had cerebrovascular disease, and one had a psychotic illness. These factors are less likely to be secondary causes of tics (were absent in a large series looking at factors associated with secondary tics),⁸ and therefore these cases are included in Table 1. Patients included in the only published case series of idiopathic adult-onset dystonic tics were reportedly screened for the presence of secondary tics,²⁵ although no further history is provided. These are also included in Table 1.

Prevalence

There have been no studies to date that have ascertained the prevalence or incidence of adult-onset tic disorders in the general population. This may be due to lack of interest on the part of the tics community, or the difficulties inherent in obtaining an accurate prevalence in this population. Patients and family members are often unaware that they have tics, and the waxing and waning nature of tics renders them a moving target for ascertainment.^19,38 There are a handful of prevalence studies involving adults with TS that could provide some idea of the prevalence of adult-onset tics, but even these are quite few in comparison to the number of prevalence studies done in children.^39–46 In three of these studies, the population consisted of adolescents aged 16–17 years who were undergoing health screening for military service in Israel,^39,40,46 and therefore not necessarily representative of the 18+ adult population. A few studies have looked at all tic disorders, thereby including secondary tics as well. One study of 50–89 year olds reported on the prevalence of all tic disorders⁴⁴ in a population-based survey of men and women in northern Italy, and found that three out of 706 individuals (0.4%) had tics.⁴⁴ One patient had TS, and two had simple motor tics. Schlander et al.⁴³ performed a retrospective review of outpatient claims data of 2.2 million individuals and calculated the prevalence of all tic disorders and TS. The prevalence of any tic disorders in both genders aged 19 years and above was 0.08%,⁴³ which was higher than the prevalence of TS (0.005%). One of the few studies providing an actual estimate of the prevalence of adult-onset tics was carried out on an inpatient psychiatric ward.⁴¹ Interestingly this study did not find an elevated rate of TS, which would be expected given the psychiatric comorbidity associated with TS; in fact no patients met the criteria for TS. However, 10 out of 200 (0.05%) patients reported in an interview that motor or vocal tics had been present for less than 1 year. Two patients demonstrated motor tics during the evaluation but did not provide a history of tics. These patients could either have had undiagnosed tics since childhood, or adult-onset tics. If these two patients are included, then the prevalence of adult-onset tics in this population is 0.06%. Most recently, a population-based survey study in Canada assessed prevalence in adults but focused on TS rather than tics in general; they report a prevalence of 0.09%.⁴⁵ An accurate estimation of the prevalence of adult-onset tics is therefore very difficult based on the available data, and would require a population-based study specifically addressing this question.

Comorbidities

The prevalence of comorbidities in adult-onset tics has not been systematically studied. In TS, ADHD is the most common comorbidity and affects up to 60% of patients, particularly boys, and its presence is associated with earlier tic onset.⁴⁷ The prevalence of OCD in TS varies between 19% and 66%, depending on whether obsessive compulsive traits or behaviors are included.⁴⁷ A Japanese study of 31 adults with childhood-onset tic disorders found that 16.1% had ADHD, 74.2% had obsessive compulsive symptoms, 12.9% had anxiety, and 35.5% had self-injurious behaviors.⁴⁸ Chouinard and Ford⁵ report that of their 22 patients with adult-onset tics, which includes both childhood recurrence and secondary tics, 41% of patients had a history of OCD, which was the most common psychiatric comorbidity in this group. In Eapen et al.’s⁴ report of eight patients with adult-onset idiopathic tics (this includes five patients who may have secondary tics depending on interpretation), four displayed OCB or obsessive traits, two had no psychiatric comorbidity, one had depression, one post-traumatic stress disorder, and one anxiety.

Of the 26 adult-onset primary tic disorders displayed in Table 1, 12 (46%) had no comorbidity, six (23%) had OCD or OCB (obsessive compulsive behavior), five (19%) had depression, five (19%) had anxiety or panic attacks, and four (15%) had other psychiatric disorders (psychosis, paranoia, hyperactivity, and drug addiction). The frequency of comorbidities is lower in this group than in TS or the above-described previous reports. Obsessive compulsive behavior was the most common comorbidity in this group, similar to the adult cases discussed above, and in contrast with children, where ADHD is the most common. This supports the possibility that adult-onset primary tics are a different entity with a separate pathophysiology from childhood-onset tics, as the associated comorbidities would be expected to differ.

Risk factors

A number of risk factors have been associated with TS including gestational and perinatal factors, drug abuse, streptococcal infections, psychologic trauma, family history of tics, and co-existent medical and psychological disorders.⁴⁹ Some of these factors would be expected to serve as risk factors in adult-onset idiopathic tics as well, such as psychiatric comorbidity, whereas perinatal factors would be expected to play less of a role. Large-scale studies have not been conducted to assess risk factors in adult-onset tics, and the past medical history is often incomplete even in individual case reports. Of the 26 adult-onset primary tics patients presented here (Table 1), 10 (38%) had a family history of tics or an associated comorbidity, and 15 (58%) had a personal history of a psychiatric disorder (OCD or obsessive compulsive trait, anxiety, panic attacks, depression, hyperactivity, psychotic symptoms, or drug addiction). This is lower than the percentage of TS patients who suffer from another psychiatric disorder (80–90%) and similar to the number who have a family history of tics (56%).⁵⁰ These comorbidities however may impact adults differently, and some have suggested that comorbidities such as anxiety and depression may be more important determinants for overall quality of life in adults with new-onset tics than in children.⁵ The biggest risk factor for tics in childhood is male sex, occurring in 77–80% of cases.^51,52 After the age of 30, the sex difference may become less pronounced.⁴³ In the adult-onset cases presented here, only 8% were female. Interestingly, the male gender preponderance endures in the case of secondary adult-onset tics. Obsessive compulsive trait and male gender are therefore probable risk factors for the development of adult-onset tics, but there are too few data to quantify the risk.

Disease course

The disease course of TS is not well delineated past early adulthood as studies have not followed patients past their late twenties, and usually not that long.^19,53,54 In the case of adults, there are no long-term follow-up studies of primary or secondary adult-onset tics. Often, patients have been followed for a number of years and in these cases, tics tend to wax and wane as they do in TS (Table 1). Chouinard and Ford⁵ found that in their adult-onset cases, duration of disease was on average 10.5 years, tics tended to wax and wane, and never completely remitted. While we lack enough information for more substantial conclusions on this topic, it seems likely that adult-onset tic disorders would follow a different disease course than that of childhood onset tics, which tend to improve with age.

Clinical features

Adult-onset tics can display a similar range of clinical features that have been seen in children. What is less well established is how they might differ in terms of anatomical location, type (clonic vs. phonic vs. dystonic), or severity. The phenomenology of tics in adults has been compared to that of children without much consensus. One study comparing the characteristics of tics in adults with children concluded that the phenomenology of adults with childhood-onset tics was similar to that of children.⁵⁵ Eapen et al.⁴ however reported that adult-onset tics were more severe, while Chouinard and Ford⁵ thought they were milder in adults than children. In a case series of tics associated with dystonia, the adult-onset group was found to have more severe tics.⁵⁶ The clinical features of previously reported adult-onset primary tics are shown in Table 1. Eleven of 26 patients (42%) displayed motor tics, 13 (50%) displayed motor and phonic tics, and (8%) had phonic tics only. As in childhood cases, the face followed by the neck and arms were the most common anatomical locations for tics.²⁰ Detailed descriptions of the appearance of tics are often lacking in published reports,^25,28 but are similar to those of childhood-onset tics. Complex vocal tics (coprolalia, palilalia, echolalia), which can be among the most impairing types of tics, are seen in adult-onset primary tics as well. In adult-onset idiopathic tics, motor and phonic tics are the most common types of tics, followed by motor tics and, lastly, phonic-only tics. As phonic tics, especially coprolalia, may lead to greater social stigmatization than motor tics,^57,58 the prevalence of these among the adult-onset cases reviewed here raises the concern that many adults suffer considerable morbidity from their tics.

Treatment

The treatment of adult-onset tics has not been given particular attention in the neurologic literature. What we know about the treatment of tics stems largely from trials involving children with TS. Tics are usually treated with one or more of the following approaches: education, medication, behavior therapy, botulinum toxin, and, rarely, deep brain stimulation surgery.^59,60 In adults with primary tics, medication has been the primary treatment method employed (Table 1). Of the 26 cases summarized in this review, two responded to verapamil, one to diazepam, one to neuroleptic, one to clonidine, one to tetrabenazine, and eight to botulinum toxin. Two were untreated. One case had incomplete treatment information. The group treated with botulinum toxin had a favorable response rate, possibly because dystonic tics are potentially more responsive to botulinum toxin than clonic tics. Botulinum toxin offers the advantage of causing no systemic side effects, which in the case of neuroleptic-induced tardive syndromes can be severe, embarrassing, and debilitating. Despite evidence of its efficacy in tics,⁶¹ and low risk of tardive dyskinesia compared with neuroleptics^62,63 tetrabenazine was not utilized often, possibly because of its cost and side-effect profile (mainly depression and somnolence). The related compounds deutetrabenazine and valbenazine show promise as alternatives to tetrabenazine with fewer adverse effects and decreased dosing frequency.^64,65 Overall, the treatment of adult-onset tics remains a challenge because of poor and unsustained response rates, and the risks and benefits of medication need to be weighed in relation to the impairment caused by the tics themselves.

Conclusion

The current review constitutes the first comprehensive review of the literature of adult-onset primary tic disorders. Adult-onset tics can be roughly categorized into three groups: primary or idiopathic tics, secondary tics, and childhood-recurrent tics. A rigorous distinction between these groups has not been made in the literature, which produces some challenges for this subject. In addition, tics themselves are quite heterogeneous in terms of their phenomenology, and even specialists may find it difficult to agree on whether to classify certain movements as tics or a different hyperkinetic movement. What is clear from this review is that the descriptions of adult-onset tics remain few, and longer-term or epidemiologic studies are completely absent. While the lack of data suggests that adult-onset tics are a rare occurrence, there have been no systemic studies to evaluate this. The paucity of studies devoted to adult-onset tics may stem in part from the rarity of the disorder, but there are numerous examples of rare diseases that have benefitted from in-depth clinical research. The conception of tics as a childhood condition, and the consequent cognitive bias, may be part of the reason that there has been less interest in the adult population. The recognition that tics do occur in adults, and may even start in adulthood, is important for the proper triage and treatment of patients. It may be useful to formally recognize “adult-onset tourettism” as a diagnostic category in order to ensure this group is not overlooked. Epidemiologic studies assessing adult populations that are not combined with pediatric data would allow us to better understand the prevalence, risk factors, disease course, and comorbidities of adult-onset tics. Clinical reports that seek to better characterize the clinical factors and appearance of tics in adults would perhaps provide us with a clearer picture of their clinical manifestations. Ultimately, further research into the best treatments for adult-onset tics will help us tailor pharmacologic and non-pharmacologic therapies to this population, which until now have been mostly guided by research on children.