Frequency and significance of vocalizations in Sydenham's chorea

1. Introduction 

Sydenham's chorea (SC) remains the most common cause of acute chorea in children [1]. In addition to chorea, SC patients on neurological examination may display flaccidity, motor impersistence and hypometric saccades. Behavioral symptoms in SC include obsessions, compulsions, attention deficit and hyperactivity [1]. SC is thought to result from beta-hemolytic Streptococcus-induced antibodies which cross-react with basal ganglia antigens, the so-called anti-basal ganglia antibodies (ABGA) [2]. The combination of tics and behavioral abnormalities in some patients with Tourette's syndrome (TS) as well as reports of a high frequency of ABGA has led to the hypothesis that a subset of tic disorders may also be causally related to streptococcal infection [2], [3]. The authors of this proposal coined the acronym PANDAS (pediatric autoimmune neuropsychiatric disorders associated with streptoccocal infections) to label this particular group of disorders [3]. In light of the fact that the presence of vocal tics is an obligatory criterion for the diagnosis of TS, we decided to investigate vocalizations in patients with SC.

3. Results 

During the study period, we saw 89 subjects who met the diagnostic criteria of SC. They had a mean age±SD of 15.4±5.4 years; the majority were females (60/89). Their mean±SEM score on the USCRS was 9.2±1.4. Vocalizations were identified in seven subjects (7.8% of the cohort; 14.5±3.4 years; M/F, 4/3) whose USCRS score was 9.7±0.8. With the exception of an inversion of the gender distribution, there were no demographic or chorea severity significant differences between patients with and without vocalizations. These consisted of simple sounds, such as tongue clicking (4), throat clearing (2), and sniffing (1); in no case were they preceded by premonitory sensation; they were not situation- or stimulus-specific; and, with the exception of two subjects, the vocalizations were associated with facial chorea.

4. Discussion 

Vocal tics have been previously reported in seven patients with SC. The authors, however, did not give the percentage of their cohort of SC patients these subjects represent [5]. To our knowledge there are no other reports in the literature of abnormal vocalizations in SC. In this study we identified the presence of vocalizations in 7.8% of a large cohort (89) of subjects with SC. Caution is warranted in interpreting the statistical analysis of our data due to the small number of subjects with vocalizations. Nevertheless, patients with and without vocalizations did not differ in their demographic or clinical features, with the exception of the presence of a slight preponderance of males among those with vocalizations whereas females made up the largest proportion of the cohort as it is usually observed in SC [1]. We also demonstrated that the patients just produced simple sounds, which were neither preceded by premonitory sensations nor were they stimulus- or situation-specific; and in most instances they occurred in association with facial chorea.

It is of interest to discuss the comparison between the phenomenology of the vocalizations in our SC patients with that seen in subjects with TS. As in our patients with SC and vocalizations, in TS there is a male preponderance and simple vocal tics are the most commonly identified vocalizations in patients. However, complex tics such as coprolalia and echolalia are observed in about 25% of patients with TS. Moreover, premonitory sensations are present in at least 1/3 of subjects and, in contrast, there is no association between vocal tics and facial motor tics [6]. These discrepancies between the phenomenology of the vocalizations of patients with TS and SC suggest that the mechanism underlying the phenomenon in the two groups is distinct. We submit that in the majority of the cases the vocalizations produced by patients with SC represent sounds resulting from the involuntary choreic contraction of the pharynx and laryngeal muscles. Similar phenomena occasionally occur in Huntington's disease, Meige syndrome and tardive dyskinesia [7], [8], [9].

Our findings have several implications. (1) Because we have failed to find a high frequency of vocalizations in SC and, moreover, they do not share features with tics (such as, premonitory sensations and being stimulus- or situation-specific), our study casts doubt over the PANDAS hypothesis, i.e., that Streptococcus may play a role in the pathogenesis of tic disorders. (2) As our data suggest that vocalizations simply result from muscle contractions caused by chorea of upper respiratory muscles, the best approach to manage these findings in patients with SC is simply to optimize antichoreic treatment with measures such as valproic acid and neuroleptics. (3) Conversely, our findings do not support the use of antibiotics and/or immunosuppressive measures to manage tics in TS.

Conflict of interest 

The authors have no conflict of interest to disclose.