Objective: To prospectively assess the outcome of patients receiving botulinum toxin (BoNT) injections for upper limb tremor refractory to oral medications.

Background: Upper limb tremor is one of the most common neurological symptoms. However, depending on the aetiology, oral medications may only be of limited efficacy. Deep brain stimulation (DBS) is only appropriate in select refractory cases. BoNT for upper limb tremor has not been extensively studied, and outcomes have shown mixed results. A possible reason for this may be due to the highly variable nature of tremor between patients, and individualised approach that is required with respect to muscle and dose selection.

Methods: Patients with medically refractory upper limb tremor were assessed over a 12-month period. An individual injection plan was formulated based on both proximal and distal upper limb tremulous movements. BoNT injections were given at months 0, 3, 6, 9 and 12. To assess clinical outcomes, each patient was reviewed 6 weeks following each injection cycle. Rating scales used include the modified FTM-Tremor Rating Scale (Part A, B and C), the tremor component of UPDRS part III (3.15 – 3.18), and a quality of life (QUEST) questionnaire. Grip strength was assessed with a dynamometer.

Results: 22 patients (15 male:7 female) were assessed. The mean age was 73 years (60-85 years), with the majority of patients having had a tremor for >10 years. The main diagnoses were either dystonic (55%) or essential tremor (36%). The average dose injected per upper limb was 50 units onabotulinumtoxin A. In most cases, both limbs were injected. There was a global improvement in FTM-TRS-A, -B and -C scores following BoNT (50%, 33% and 60% reduction respectively). All domains of the QUEST questionnaire also improved. Patients reported a mean reduction in tremor during the day of 4.4 hours. 60% of patients reported that they were satisfied with tremor control. Grip strength was reduced by a mean of 24%, and was generally very well tolerated. Seven patients were discharged during the assessment period, due to poor response in four cases, excessive weakness in one, whilst two patients were lost to follow up.

Conclusions: Botulinum toxin therapy is an effective and well-tolerated treatment option for upper limb tremor that is refractive to oral medications. A careful, individualised and dynamic assessment of tremor is required for muscle and dose selection.

References: 1. Mittal Shivam, et al. A Randomized, Double-Blind, Placebo-Controlled Study With a Customized Injection Approach. Mayo Clin Proc. September 2017;92(9):1359-1367. 2. Jankovic J, Schwartz K. Botulinum toxin treatment of tremors. Neurology. 1991;41(8):1185-1188.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/botulinum-toxin-injections-in-upper-limb-tremor/