Isolated head tremor has been defined as a shaking of the head in yes‐yes, no‐no, or, variable directions. 1 Head tremor is frequent in the context of Essential tremor (ET) and it is also a common manifestation of tremulous dystonia. The relationship between isolated head tremors and focal tremulous cervical dystonia is controversial.
Botulinum toxin treatment has been frequently used in the management of head tremor. 2 However, the current evidence is unclear and ambiguous. The findings of previous studies were limited by the design of the study and the small sample size. Currently, the injections are based on tremor oscillations and doses are decided by clinical judgment.
In an attempt to address these questions, Marques et al published the findings of a multicenter, double‐blind, randomized trial of local injections of botulinum toxin for isolated or essential head tremors. 3 The study was supported by a grant from the French Ministry of Health. A total of 120 adult patients with essential or isolated head tremors were randomized in a 1:1 ratio to receive botulinum toxin or placebo. The primary outcome was measured by improvement by at least 2 points on the clinical global impression of change scale at 6 weeks after the second injection.
The authors reported that the botulinum toxin injection into bilateral splenius capitis muscle on day 0 and during week 12 was more effective than placebo in reducing the severity of isolated or essential head tremors at 18 weeks but not at 24 weeks. However, the primary outcome was met by 31% of patients in the treatment group compared with 9% of those in the placebo group. Adverse events occurred in a higher percentage of patients in the botulinum toxin group (47%) than in the placebo (16%) group (P < 0.001). The most common adverse events included head and neck pain, posterior cervical weakness, and dysphagia.
The study findings were limited by a higher incidence of loss of follow‐up of patients in the botulinum toxin group, and the influence of external physiological factors such as stress, anxiety, and profession increasing the amplitude of tremor in some patients. Also, there was partial unmasking due to higher doses in some patients owing to the lack of efficacy of the first dose and injecting physicians having access to electromyographic findings. Furthermore, the study findings may not be generalizable to patients with head tremors associated with cerebellar syndrome.
Despite these limitations, the trial findings are important considering the large sample size. However, future studies should include more muscles like obliquus capitis inferior which are frequently implicated in the head tremor, and injection into this deep muscle has improved the outcome. 4 Ultrasound‐guided injections may also be used in prospective studies which is likely to decrease the adverse events as it may help in better assessment of the depth and thickness of injected muscles. 5
Author Roles
(1) Research project: A. Conception, B. Organization, C. Execution; (2) Statistical Analysis: A. Design, B. Execution, C. Review, and Critique; (3) Manuscript: A. Writing of the first draft, B. Review, and Critique.
S.P.: 1A, 1B, 1C, 2A, 2B, 2C, 3A, 3B
Disclosures
Ethical Compliance Statement: We confirm that the approval of an institutional review board was not required for this work. We also 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: No specific funding was received for this work. The authors declare that there are no conflicts of interest relevant to this work.
Financial Disclosures for the Previous 12 Months: The authors declare that there are no additional disclosures to report.
Potential conflict of interest: None.
Funding agency: None.
References
- 1. Bhatia KP, Bain P, Bajaj N, et al. Deuschl G; Tremor Task Force of the International Parkinson and Movement Disorder Society. Consensus Statement on the classification of tremors. From the task force on tremor of the International Parkinson and Movement Disorder Society. Mov Disord 2018. Jan;33(1):75–87. 10.1002/mds.27121. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 2. Ferreira JJ, Mestre TA, Lyons KE, et al. MDS evidence‐based review of treatments for essential tremor. Mov Disord 2019;34(7):950–958. 10.1002/mds.27700. [DOI] [PubMed] [Google Scholar]
- 3. Marques A, Pereira B, Simonetta‐Moreau M, et al. Trial of botulinum toxin for isolated or essential head Tremor. N Engl J Med 2023;389(19):1753–1765. 10.1056/NEJMoa2304192. [DOI] [PubMed] [Google Scholar]
- 4. Pandey S, Kreisler A, Drużdż A, Biering‐Sørensen B, Sławek J, Tatu L, Jost WH. Tremor in idiopathic cervical dystonia‐possible implications for botulinum toxin treatment considering the col‐cap classification. Tremor Other Hyperkinet Mov (N Y) 2020;7(10):13. 10.5334/tohm.63. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 5. Hong JS, Sathe GG, Niyonkuru C, Munin MC. Elimination of dysphagia using ultrasound guidance for botulinum toxin injections in cervical dystonia. Muscle Nerve 2012;46(4):535–539. 10.1002/mus.23409. [DOI] [PubMed] [Google Scholar]