Median nerve stimulation (MNS) at 10-12 Hz was recently proposed as a potential treatment for tics in Tourette syndrome and other chronic tic disorders (TS/CTD). Here we report on 31 people ages 15-64 with TS/CTD who participated in a 4-week open label study of MNS, 27 of whom completed the final survey. They reported tic frequency and intensity each time they began or ended stimulation, and twice daily at random times between 09:00 and 21:00 when prompted by a text message. They also reported tolerability of stimulation when the device was on. Reported MNS use was 50 minutes per day used (median; interquartile range [IQR] =93 minutes) with the average participant using the device 1.5 days per week (median, IQR=1.4). Tic frequency improved during MNS (1.0 mean difference on a 0-5 scale, p <0.001), as did tic severity (0.9 mean difference, p <0.001). Mean discomfort during stimulation was 1.2, signifying mild discomfort. 78% of participants reported they planned to continue using the device after the study ended. Participants’ results in this study did not correlate significantly with their results in the preceding blinded, randomized, controlled trial. However, improvement in tic frequency on ratings performed during the study period did correlate with participants’ perception of overall therapeutic benefit at the conclusion of the study (R=−0.58, p=0.005). Symptom improvement did not clearly persist after a stimulation session ended. We did not detect significant differences between participants who reported overall therapeutic benefit during the study period and those who did not. One of the most common suggestions by participants was for a more unobtrusive form factor. We provide individual participant data.

A prior study showed that rhythmic, but not arrhythmic, 12 Hz stimulation of the median nerve (MNS) entrained the sensorimotor cortex EEG signal and found that 10 Hz MNS improved tics in Tourette syndrome (TS). However, no control condition was tested, and stimulation blocks lasted only 1 min. We set out to replicate the TS results and to test whether tic improvement occurs by the proposed cortical entrainment mechanism. Preregistration was completed at ClinicalTrials.gov, under number NCT04731714. Thirty-two people with TS, age 15–64, completed two study visits with repeated MNS on and off blocks in random order, one visit for rhythmic and one for arrhythmic MNS. Subjects and staff were blind to order; a video rater was additionally blind to stimulation and to the order of visits and blocks. Rhythmic MNS at 10 Hz improved tics. Both rhythmic and arrhythmic 12 Hz MNS improved tic frequency, intensity, and urges, but the two treatments did not differ significantly. Participant masking was effective, and there was no carryover effect. Several participants described a dramatic benefit. Discomfort was minimal. There was no evidence that the MNS benefit persisted after stimulation ended. These results replicate the tic benefit from MNS but show that the EEG entrainment hypothesis cannot explain that benefit. Another electrophysiological mechanism may explain the benefit; alternatively, these data do not exclude a placebo effect.

Recent years have seen a dramatic increase in new “tic” cases in teens and young adults. These individuals often present with fulminant onset of distinct symptoms not commonly seen in Tourette syndrome (TS), and are often diagnosed with Functional Neurological Disorder (FND-tic). Some have questioned whether this illness truly differs from typical Provisional Tic Disorder (PTD) and Tourette syndrome. Here we address this concern by providing for the first time substantial data on clinical features during the first year after symptom onset in 89 patients with PTD who later were diagnosed with TS. Several clinical features dramatically distinguish the rapid-onset FND-tic patients from patients with typical PTD. For example, coprophenomena are reported at or shortly after symptom onset in over half of FND-tic patients, whereas we observed coprophenomena at presentation in only 1 of 89 children with PTD. A handful of clinical features have a positive predictive value (PPV) over 90%. These new data provide strong evidence supporting the diagnostic validity of FND-tic as distinct from TS.

Background: Recent years have seen a dramatic increase in new “tic” cases in teens and young adults. These individuals often present with fulminant onset of symptoms not commonly seen in Tourette syndrome (TS) and are often diagnosed with Functional Neurological Symptom Disorder (FND-tic). However, some authors have questioned whether this illness truly differs from typical Provisional Tic Disorder (PTD) and TS. Previous studies have compared FND-tic, usually a few months after symptom onset, to patients with TS, usually years after symptom onset. We sought to test whether the presenting symptoms of FND-tic differ substantially from those in patients at a similar duration of symptoms who are later diagnosed with TS. Methods: This comparative study examines clinical features summarized from published reports of FND-tic with novel data from a longitudinal study of PTD. This study came from a referral center for TS and tic disorders and included 89 children with tics whose first tic occurred a median of 3.6 months earlier, nearly all of whom were diagnosed with a chronic tic disorder at follow-up. Specifically, we examine clinical features identified in a recent literature review as supporting a diagnosis of FND-tic, including symptom characteristics, course, severity and comorbidity. Results: Several clinical features dramatically distinguish the patients diagnosed with FND-tic from those diagnosed with typical PTD. For example, coprophenomena are reported at or shortly after symptom onset in over half of FND-tic patients, whereas even several months after onset, coprophenomena had occurred in only 1 of 89 children with PTD. Six clinical features each have a positive predictive value over 90% for FND-tic diagnosis if prior probability is 50%. Conclusions: These new data provide strong evidence supporting the diagnostic validity of FND-tic as distinct from TS.

Median nerve stimulation (MNS) at 10–12 Hz was recently proposed as a treatment for Tourette syndrome and other chronic tic disorders (TS/CTD). We report on 31 participants ages 15–64 with TS/CTD in an open-label, comparative (within-group, several time points) study of MNS (ClinicalTrials.gov registration number NCT05016765). Participants were recruited from completers of a randomized controlled trial (RCT) of MNS and were given a transcutaneous electrical nerve stimulation (TENS) unit to use as desired for 12 Hz MNS for 4 weeks. Participants were instructed to complete surveys regarding tic symptoms and stimulation discomfort before and after stimulation, as well as twice daily when randomly prompted by text message. Participants also completed an extensive final survey. Twenty-seven participants completed the study. Median device use was 1.5 days per week and 50 min per day used. Tic frequency improved during MNS (mean improvement: 1.0 on a 0–5 scale, p < 0.001), as did tic intensity (mean improvement: 0.9, p < 0.001). Mean discomfort was mild (1.2 on a 3-point scale). In total, 21 participants (78%) planned to continue using the device. Participants’ results in this study did not correlate significantly with their results in the blinded RCT. We found MNS to improve tic frequency and intensity with minimal side effects.