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Introduction
Sensory tricks, defined as ‘episodic and specific manoeuvres that temporarily improve dystonia in a manner that is not easily physiologically perceived as necessary to counteract the involuntary movement’, are well-recognised features of organic dystonia.1 The term ‘alleviating manoeuvres’ (AlM) has been proposed as a more appropriate term because ‘sensory trick’ suggests that only sensory input is required, and the word ‘trick’ wrongly implies that is ‘fake’.2 ‘Reverse sensory trick’ is the term used when a manoeuvre worsens dystonia, the latter can also be called ‘aggravating manoeuvres’ (AgM). AlMs are usually internally generated and rarely effective when applied by another person. However, patients with functional (psychogenic) movement disorders (FMDs) may show improvement or aggravation with stimuli applied by another person, that is, examiner manoeuvre (EM). In this study, we aimed to assess the frequency and characterise the clinical features of EMs in a large cohort of patients with FMDs.
Patients and methods
We reviewed medical records and video recordings of all cases of FMDs evaluated at Baylor College of Medicine Movement Disorders Clinic during a 2-year period. We assessed the stimuli type that improved or worsened the movements and which FMDs they influenced; in some cases patients reported such tricks, in other cases, they were discovered during the clinical examination. Additionally, in a proportion of these patients, we assessed the effect of a vibrating tuning fork placed on the body part involved in the ‘involuntary’ movement or some other body area if there was no ongoing movement, as in paroxysmal FMDs. Before applying the tuning fork, the patients were told that ‘sometimes vibration may improve or worsen these type of movements’ avoiding potentially deceiving statements such as ‘my tuning fork has magic powers…’, etc. All patients or their legal guardian signed written informed consent for videotaping approved by our Institutional Review Board for Human Research.
Results
We studied 184 consecutive patients with FMDs. From this cohort, we identified 55 patients (30%) with an effect of EM; 22 (12%) patients had AlM, 36 (20%) patients had AgM; 3 of these patients had both types of manoeuvres. Tremor and dystonia were the most common FMDs for which both types of manoeuvres were effective, but EM did not influence more frequently any particular FMD. A variety of stimuli were present in AlM and AgM including vibratory, proprioceptive, tactile, auditory, kinetic, nociceptive and complex stimuli (table 1). The effect of vibration by means of a 128 Hz tuning fork on the FMDs was recorded in 49 patients, in which 9 (18.4%) showed improvement or resolution, in 27 (55%) there was worsening or the movement was triggered by the vibrating stimulus (see online supplementary videos 1 and 2). No clear effect was noted in 13 (26.5%) of patients.
Clinical features of AlM and AgM from this series
supplementary video
supplementary video
No differences in gender distribution (p=0.686), and age at onset (p=0.136) was observed between patients with FMDs affected or not by EM. Patients with functional hemifacial spasm distributed more frequently among patients with AgM than those without it (p=0.004).
Discussion
In this study, we examined the frequency and characteristics of EM in patients with FMDs. Although the pathophysiology of EM in patients with FMDs is unknown, such pathophysiology is likely different to organic dystonia, with a possible role of suggestibility. Contrasting features of AlM/AgM between organic dystonia and FMDs are summarised in the online supplementary table.
supplementary table
We recorded the effect of EM on FMDs, interestingly several types of stimuli alleviated or aggravated the movements; furthermore, we assessed the effects of a vibrating tuning fork to either trigger/worsen or abolish/improve the movement. The primary goal of this intervention was to better characterise the movement disorder. We took precautions not to deceive or appear to deceive our patients by explaining to them that the use of the tuning fork helps us to better understand the nature of the movement disorder.3 The tuning fork was also used to trigger the movement in patients with intermittent or paroxysmal FMDs who did not manifest the movement while in the clinic and in whom we would otherwise have no opportunity to observe the described movement. Moreover, the EM helped us to support the diagnosis of FMD, a diagnosis that should be based on positive clinical findings. The EM helps patients to understand the nature of the movements when the manoeuvre is explained increasing the diagnostic certainty without necessarily producing a permanent placebo effect and thus the technique has a potential therapeutic role.4 For example, patients in whom a vibrating tuning fork alleviates the abnormal movement may benefit from transcutaneous electrical nerve stimulation.5
Our study has limitations, including the retrospective nature of the search for cases in our database that had EM; however, we included all patients reporting EM within the study period recorded on videos. Further studies should include standardised administration of the EM to patients with FMD in order to explore their sensitivity, specificity and potential therapeutic role in FMDs.
Conclusions
In conclusion, EMs are observed in organic movement disorders, and also in patients with FMDs, although less frequently and with contrasting features compared with organic dystonia. EM may help characterise the underlying FMDs.
Footnotes
Contributors JFB-C gathered the data, made the statistical analysis, conceptualised and wrote the first draft of the manuscript. JJ gathered the data, conceptualised and reviewed the manuscript.
Competing interests None declared.
Patient consent Obtained.
Ethics approval This is a retrospective, observational study, but patients signed written informed consent to be videotaped and release of specific health information for research and educational purposes such as publishing in professional journals.
Provenance and peer review Not commissioned; internally peer reviewed.