Are Cognitive Symptoms Part of the Phenotypic Spectrum of Idiopathic Adult-Onset Dystonia? Summary of Evidence from Controlled Studies

BACKGROUND

Cognitive dysfunction has been reported in idiopathic adult-onset dystonia (IAOD), but whether this is a primary or secondary component of the disorder remains uncertain.

OBJECTIVE

Here, we aimed to analyze the key domains of abnormal cognitive performance in IAOD and whether this is associated with motor or mood changes.

METHODS

Article selection for our critical review was guided by PRISMA guidelines (mesh terms "dystonia" and "cognitive," publication period: 2000-2022). Only peer-reviewed, English-language original case-control studies involving patients with IAOD who were not exposed to dopamine- or acetylcholine-modulating agents and validated cognitive assessments were included.

RESULTS

Abstract screening ultimately yielded 22 articles for full-text review and data extraction. A greater proportion of studies (17 of 22, 82%) reported abnormal cognitive performance in IAOD. Most of these studies focused on blepharospasm (BSP) and cervical dystonia (10 and 14, respectively). Most studies reporting cognitive impairment (11 of 17) identified multidomain impairment in cognition. Executive functions were the domain most frequently explored (14 of 22 studies), 79% of which detected worse performance in people with dystonia. Results related to other domains were inconclusive. Cognitive abnormalities were independent of motor symptoms in most studies (7 of 12) that explored this relationship and independent of mood status in all 8 that investigated this.

CONCLUSIONS

Within IAOD, cognitive dysfunction (in particular, executive dysfunction) has been documented mainly in BSP and cervical dystonia. More comprehensive testing is warranted to assess abnormalities in other domains and in other forms of IAOD, as well as to evaluate longitudinal progression of cognitive disturbances in this condition.

Adult-Onset Primary Dystonic Tics: A Different Entity?

Based on their phenomenology, tics can be classified as clonic, dystonic, and tonic. Although tic syndromes are considered to be childhood disorders, there are reports on (clonic) tics developing late in life. Literature on dystonic tics is sparse, and it is unclear whether adult-onset dystonic tics are part of the same disorder spectrum that includes Tourette's syndrome or represent a discrete entity. We describe here 11 patients with adult-onset primary dystonic tics. Ten patients (90.1%) were males. Mean age at onset was 42.2 ± 14.9 years. More than 60% had both motor clonic and dystonic tics. Dystonic tics most frequently involved the cranial-cervical region and the shoulders and, less frequently, the limbs. Psychiatric comorbidities were present in 5 patients. Family history for any movement disorder or for psychiatric disorders was present in 2 cases. One patient showed a sensory geste, which allowed him to partially control his tics, whereas another developed overt dystonia 3 years after his first assessment. The hyperkinesias exhibited by these patients were likely consistent with tics. However, other clinical features would allow us to argue that adult-onset dystonic tics may represent a discrete entity, which is intermediate between tics and dystonia.