Adult‐Onset Primary Dystonic Tics: A Different Entity?

Patients and Methods

From our database of 253 patients with tics, we found 21 with dystonic tics. Ten patients were excluded because tic onset preceded 18 years of age. The remaining 11 (52.4%) reported tic onset in adulthood. We included only patients in whom tics were the only movement disorder clinically observed at first assessment, thus excluding those in whom there was also a suspicion of concurrent dystonia at first assessment (i.e., patients with a combination of motor tics and dystonia, already published11). All patients were examined by the same experienced movement disorder specialist (K.P.B.). Secondary tic causes were excluded by clinical interview and appropriate investigations (all patients underwent brain MRI, and further investigations, including extensive blood tests, acanthocytes, electromyography, genetics and others, have been pursued according to the discretion of the supervising physician). Clinical data, including clinical presentation and age at symptoms onset, phenomenology of tics and their localization, and coexistent psychiatric disorders, were collected from medical records. Treatment, follow‐up, and family history were also ascertained.

Results

Of 11 patients with dystonic tics, 10 (90.1%) were males. Mean age at onset was 42.2 ± 14.9 years (range, 25–70). All 11 patients stated that tics developed after 18 years of age, and this was confirmed by at least one relative. Demographics and clinical characteristics of these patients are detailed in Table 1. The majority (63.6%) had both motor clonic and dystonic tics. These patients were not able to subjectively differentiate between such two types of tics, and thus the age at onset reported here refers to the first appearance of either dystonic or clonic tics. The 2 patients (cases 10 and 11) who showed only phonic, along with dystonic, tics stated that both types of tics developed at the same time.

Dystonic tics most frequently involved the cervical region (90.1%; tilting, turning, or flexion of the head), the cranial region (45.5%; eye closure or jaw involvement), shoulders (36.4%; shrugging or rotation), and, less frequently, limbs (9%; leg flexion). Seven patients (63.6%) also had clonic motor tics, whereas 5 (45.5%) also had phonic tics. Premonitory urges and suppressibility were present in 72.7% of cases. There was no gross phenomenological difference of either dystonic or clonic/phonic tics between patients with and without urges/suppressibility. All patients reported fluctuations in the intensity and frequency (waxing and waning) of their tics. Regarding the waxing and waning nature of their disorder, all patients but 2 were eventually bothered by their tics to seek medical attention. Of interest, one patient (case 1) also had a sensory geste, which allowed him to partially control his tics (see Video).

Psychiatric comorbidities were present in 5 patients (45.5%). In 3 patients, psychiatric issues developed after onset of tics. Two patients were suffering from mild depression and 1 from a mild anxiety disorder, for which no pharmacological treatment was commenced; 1 patient had a panic disorder and a suggestion of paranoid psychosis before the onset of tics, but had been treated only with benzodiazepines; finally, 1 patient had multiple psychiatric comorbidities comprising substance use disorder, anxiety, and depression, all with onset after the first appearance of tics, treated with antidepressants and antipsychotics. Family history for any movement disorder or for psychiatric disorders was present in only 2 cases (18.2%), 1 with a family history of depression and the other with a family history of benign tremor. After a mean follow‐up of 3.5 years (range, 3 months to 7 years), tics did not significantly worsen over time in 10 of the 11 patients (90.1%). One patient (case 10) never required any treatment for his tics; 1 patient (case 5) also reported not being disturbed by his tics and did not pursue further treatments after an initial disappointing response to botulinum toxin (BoNT) injections; all other patients showed partial (1 of 9) to excellent (8 of 9) response to BoNT injections. One patient (case 7) developed overt cervical dystonia 3 year after his first assessment.

Discussion

There are few descriptions of adult‐onset tics in the literature6, 7, 11 and thus their true prevalence remains unknown, because the phenomenon has not been systematically assessed. It has been estimated that approximately half of the reported cases represent recurrences of childhood tic disorders, whereas other cases have been reported to be secondary to several underlying conditions.12 As such, primary tics manifesting during adulthood have been occasionally described. As far as we know, 32 patients with adult‐onset primary tic disorders have been described to date, including the 12 patients with tics and dystonia that we have previously published reports on.6, 7, 11 According to the described phenomenology, all of them had clonic motor tics, whereas no report exists on dystonic tics manifested during adulthood.

We are aware that the diagnosis of adult‐onset tics is problematic because some patients may have recurrence of childhood tic disorders and be unaware of previous tics. However, all our patients affirmed having onset of their tics after the age of 18 years, and this information was confirmed by a relative. Given their characteristics (i.e., relatively slow movements, causing a briefly sustained abnormal posture) and their localization (i.e., cranial and cervical regions), the diagnosis of dystonic tics can be challenging because they may mimic other involuntary movements in the spectrum of dystonia. However, a number of clinical features, including duration, premonitory urges relieved by performing the movement, suppressibility, growing inner tension during suppression, waxing and waning, and co‐occurrence of clonic and phonic tics, support the view that the hyperkinesias exhibited by these patients were consistent with the classical description of tics. Moreover, we carefully selected patients with no overt dystonia at the time of first assessment. Furthermore, in our series, approximately 90% were males, which would be very unusual for adult‐onset cranial‐cervical dystonia,13 but is common for primary tic disorders.14 Table 2 highlights similarities and differences between our patients and the classical description of tics and dystonia.

In a comparison of our patients to the series of adult‐onset tic disorders by Chouinard and Ford6 and Eapen et al.,7 we note that the male/female ratio is similar (10:1 vs. 7:0 and 7:1, respectively), whereas our patients were older at tics onset (42  vs. 36.6 and 33.7 years, respectively). In both of these series, there was a positive family history for either psychiatric conditions or tics in approximately 50% of reported cases, whereas only 2 patients in our series (18.2%) reported a family history of neurological or psychiatric illnesses (depression and tremor).

Concomitant psychiatric disorders were present in 5 patients (45.5%), of whom 3 developed their psychiatric symptoms after the tics onset, which is comparable to previous reports.6, 7 However, whereas the most common psychiatric comorbidity in the 2 previous series was obsessive‐compulsive disorder, our patients reported mainly depression and anxiety.6, 7 Furthermore, all the patients described by Eapen et al. had a possible trigger event, including infections or drug exposure,7 which instead was not observed in our cases. The observed clinical differences between our series of adult‐onset dystonic tics and previous series of patients with adult‐onset tics led us to speculate that adult‐onset dystonic tics may represent a discrete entity that does not fall within the spectrum of TS. Of interest, 1 patient had also a sensory geste, which allowed him to partly suppress his tics, whereas another patient further developed dystonia 3 years after his first assessment. Sensory gestes have been occasionally described in patients with tics, but, interestingly, all the 16 patients previously reported on were affected by dystonic tics.8, 9 Moreover, it is also noteworthy that, in our series, all patients who did not report a classic premonitory urge associated with their tics also did not exhibit any psychiatric comorbidities, which is the case in only a minority of patients with chronic tics who seek medical attention.15 This suggests that dystonic tics might either belong to the dystonia spectrum or represent a phenomenon that is intermediate between tics and dystonia. However, it is remarkable that for such an apparently rare entity as adult‐onset idiopathic tics, so many patients manifest dystonic tics (11 patients of the 43 cases described in the literature [25.6%]) or co‐occurrence of dystonia (12 of 43 cases [27.9%]).11

There are, of course, a number of features in these patients that do not entirely fit with the classical description of tics. Given that adult‐onset tics are quite rare, one would consider the diagnosis of a primary tic disorder only if all clinical tic characteristics other than age were to be fulfilled, which was not entirely the case here. On the other hand, we have a long‐standing experience of hyperkinetic movement disorders, including tics and dystonia, and we feel reluctant to label these patients as having classical dystonia. In fact, age at onset, male preference, the intermittent and stereotyped nature of the hyperkinesias, their suppressibility, the presence of a premonitory feeling, and the phenomenology of the hyperkinesias exhibited (which were relatively fast) are all against the classical presentation of dystonia. Also, another condition, which one would keep in mind in the differential diagnosis, is that of functional (psychogenic) tics. Baizabal‐Carvallo and Jankovic have recently described 9 such patients,16 and there are a number of reasons, including female preference, absence of premonitory feeling, and presence of other psychogenic movement disorders, for which we believe this diagnosis is rendered unlikely in our patients.

In summary, we have here described a cohort of patients who exhibit a phenomenon that, by way of its characteristics, is an overlap of tics and dystonia, set in an intermediate terminological position between the two. Whether this indicates shared pathophysiological underpinnings between tics and dystonia remains, however, unknown, because it is difficult to draw conclusive parallels between the two hyperkinesias.

Tic disorders and some forms of focal dystonia (e.g., blepharospasm and cervical dystonia) might share pathophysiological mechanisms. It has been, in fact, reported that in both there is enhanced excitability of brainstem interneurons, evidenced by abnormal blink reflex recovery cycles.17, 18 However, there are currently no conclusive models for any of the two disorders and the study of heterogeneous populations characterizes reported results in both.19, 20 Finally, no study addressing the pathophysiology of primary tic disorders has explicitly focused on patients with a preponderance of dystonic tics.

We acknowledge some limitations. First, this is a retrospective study, and, as such, some information may have been missed. For instance, many of our patients did not undergo any formal psychiatric assessment. However, major psychiatric disturbances were evaluated for all patients at bedside interview and further psychiatric assessment was pursued in appropriate cases. We also acknowledged that the diagnostic workup to exclude symptomatic tics has been different among our patients. We relied on the clinical history and our experience to pursue the appropriate investigations for each patient, and in this context, we also note that there were a number of clinical features in our patients that were highly suggestive of a primary disorder. Finally, as also demonstrated in the submitted video, phenomenological heterogeneity characterized the hyperkinetic movements, thus rendering their conclusive clinical categorization. In the absence of markers for the diagnosis of movement disorders, clinical experience plays a pivotal role. We feel that, although heterogeneous, these patients best fit the clinical label of dystonic tics for the reasons extensively described above, but this remains, of course, open to discussion. Adult‐onset dystonic tics may be under‐reported. On the other hand, we acknowledge that this phenomenon might have been over‐reported in our clinical series from a tertiary referral center, where there is increased probability of referral of more severe, diagnostically challenging cases. Despite this, we here provide a characterization of the main clinical features of adult‐onset dystonic tics, which supports the rationale for a more systematic exploration of this unusual phenotype in larger clinic‐ and service‐based series of patients with chronic tics.

Financial Disclosures

R.E. is partly supported by COST Action BM1101 (reference: ECOST‐STSM‐BM1101‐160913‐035934). C.G. academic research support from Deutsche Forschungsgemeinschaft (MU1692/2‐1 and GA 2031/1‐1) and European Science Foundation; commercial research support: travel grants by Actelion, Ipsen, Pharm Allergan, and Merz Pharmaceuticals. K.P.B. receives royalties from the publication of Oxford Specialist Handbook Of Parkinson's Disease and Other Movement Disorders (Oxford University Press, 2008) and of Marsden's Book of Movement Disorders (Oxford University Press, 2012) and received funding for travel from GlaxoSmithKline, Orion Corporation, Ipsen, and Merz Pharmaceuticals.

Author Roles

(1) Research Project: A. Conception, B. Organization, C. Execution; (2) Statistical Analysis: A. Design, B. Execution, C. Review and Critique; (3) Manuscript: A. Writing of the First Draft, B. Review and Critique.

R.E.: 1A, 1B, 1C, 3A, 3B

D.M.: 1A, 3A, 3B

C.G.: 1C, 3A, 3B

J.D.: 1C, 3B

A.B.: 1C, 3B

K.P.B.: 1A, 3B

Supporting information