The Need to Tic.

Abstract

Botulinum toxin (BoNT) injections are commonly used to treat focal motor and vocal tics. However, rigorous studies on BoNT efficacy and tolerability in this field are lacking.1 In our experience, BoNT is effective and well-tolerated in the treatment of tics, and the discontinuation rate due to inefficacy is very low. Importantly, the mechanism of BoNT-related tic improvement remains unclear. Kwak et al.2 suggested that BoNT injections might lead to a reduction in both the intensity of premonitory urges and tics in patients with Tourette syndrome (TS), as noted in 21/25 of their cases. In contrast to this observation, we report 3 patients with TS who decided to discontinue BoNT because the resulting muscle paralysis prevented tic occurrence and the subsequent relief of their premonitory urges. Patient 1 is a 27-year-old female presenting with simple and complex motor tics as well as a history of simple vocal tics (coughing, sniffing). The current phenomenology includes head jerks and eye movements to the left, eye winking, eyebrow raising, frowning, and pushing the tongue up in her mouth. She also reported to have an obsessive personality with superstitious beliefs. We treated her with BoNT injections only once, delivering a total dose of 60 U of AboBoNT/A to the frontalis, the corrugator and the orbicularis oculi muscles bilaterally. Patient 2 is a 43-year-old male with simple motor tics involving his neck (side-to-side head jerks) and shoulder since early childhood and occasional vocal tics (coughing). He describes himself as a perfectionist but denies obsessive–compulsive features. He was treated once with a total dose of AboBoNT/A 100 U, 50 U in each splenius capitis. Patient 3 is a 25-year old female who shows simple (e.g. eyebrow movements, eye rolling) and complex (e.g. stomping legs on the floor) motor tics, and simple phonic tics (e.g. repetitive coughing). She received BoNT injections only once in both orbicularis oculi and frontalis muscles, for a total dose of 36 MU of IncoBoNT/A. Although BoNT led to a substantial improvement of the targeted tics in all 3 patients, they declined to pursue BoNT treatment due to increased salience of premonitory urges. They felt frustrated for still experiencing the need to tic in the treated areas, without being able to do so due to BoNT-induced muscle weakness. The pathophysiology of sensory symptoms associated with tic disorders is poorly understood. The negative reinforcement hypothesis views tics as operant behaviors to alleviate the aversive experience of premonitory urges.3 BoNT prevents tics by inducing a certain degree of paralysis in the injected muscles. It might also play a role in disrupting the impaired sensory feedback in tic disorders, therefore reducing the intensity of premonitory sensations, as previously reported.2 However, not all patients may share this improvement, and indeed the only randomized control study previously performed to assess BoNT efficacy for treating tics in primary tic disorders also documented a case where there was an increase of premonitory urges, despite the reduction of motor tics.4 Of note, a similar dissociation between tic improvement and persistence of aversive somatic experiences (“sense of inner tension”) was also previously reported in an adult who was treated with bilateral deep brain stimulation of the internal globus pallidus.5 Taken together, our cases highlight the substantial heterogeneity of tic disorders, particularly with regard to treatment response, and characteristically illustrate that in some patients we can successfully treat the tic, but not the need to tic. (1) Research Project: A. Conception, B. Organization, C. Execution; (2) Statistical Analysis: A. Design, B. Execution, C. Review and Critique; (3) Manuscript Preparation: A. Writing of the First Draft, B. Review and Critique. G.D.L.: 1B, 1C, 3A F.M.: 1B, 1C, 3A C.G.:1B, 3A, 3B K.B.: 1A, 3B Dr. Di Lazzaro and Dr. Magrinelli contributed equally to this work. Ethical Compliance Statement: The authors confirm that the approval of an institutional review board was not required for this work. We confirm that we have read the Journal's position on issues involved in ethical publication and affirm that this work is consistent with those guidelines. Funding Sources and Conflicts of Interest: The authors report no sources of funding and no conflicts of interest. Financial Disclosures for Previous 12 Months: Giulia Di Lazzaro and Francesca Magrinelli are supported by the EAN research fellowship 2020. Christos Ganos holds research grants from the VolkswagenStiftung (Freigeist Fellowship) and the German Parkinson Society and was also supported by the Deutsche Forschungsgemeinschaft (GA2031/1-1and GA2031/1–2). Kailash P. Bhatia holds research grants from EU Horizon 2020 and has received honoraria to speak at meetings or to attend advisory boards from Ipsen, Cavion, Allergan, Teva Lundbeck, and Bial pharmaceutical companies. He also receives royalties from Oxford University Press and a stipend for MDCP editorship.