Objective: To assess improvement in hand function following therapy with botulinum toxin in patients with dystonic tremor (DT).

Background: Treatment of dystonic tremor (DT) with botulinum toxin (BT) injections, although often performed, still does not have an approved indication, and evidence of its effectiveness is limited [1]. Current methods of assessment of BT efficacy are mostly based on clinical scales, thus suffering from a lack of objectivity. Device-led evaluation includes the use of surface electromyography and accelerometry. However, DT often lacks a clear frequency peak, thus making their use difficult. Moreover, these methods do not fully take into account actual hand function, which is an important item when assessing therapeutic efficacy of BT.

Method: We recruited nine patients (4 female, age 70.5±8.2, disease duration 16.2±14.1 years) with DT, which were assessed the same day of their BT injections in forearm muscles, and at the peak of the effect (42.2±10.9 days). Assessment included the nine-hole peg test, the box and blocks test and the Fahn-Tolosa-Marin tremor scale (FTMTS). Additionally, manual dexterity was assessed by a strength-dexterity (SD) task [2,3]. This entails the use of force transducers mounted on a compliant and slender spring prone to buckling at very low forces. The maximal level of sustained compression is informative of the greatest instability the person can control, and thus is indicative of the sensorimotor mechanisms for dexterous manipulation [3]. Comparisons between variables measured at baseline and at the peak effect were made by means of paired t-tests.

Results: Scores in the box and blocks test and the nine-hole peg test were not affected by BT (respectively 26.4±8.1 vs 26.1±3.9 blocks, t8 = 0.154, p = 0.082, and 40.0±15.2 vs 39.1±14.9 s, t8 = 0.439, p = 0.674). By contrast, the sum of the items of the FTMTS related to the treated hand was significantly lower after BT (21.6±6.0 vs 15.1±3.9, t8 = 3.182, p = 0.015). This effect was confirmed by the SD test, which showed a significant increase in sustained compression force (0.73±0.03 vs 0.89±0.03 N, t8 = -5.136, p = 0.001).

Conclusion: The current results provide strong evidence in favour of a positive effect of BT injections in DT, confirmed by clinical assessment and supported by objective testing of sensorimotor function for hand dexterity.

References: 1 Mittal SO, Lenka A, Jankovic J. Botulinum toxin for the treatment of tremor. Parkinsonism Relat Disord. 2019 Jan 26. pii: S1353-8020(19)30023-9. doi: 10.1016/j.parkreldis.2019.01.023. [Epub ahead of print] 2 Ko NH, Laine CM, Fisher BE, Valero-Cuevas FJ. Force Variability during Dexterous Manipulation in Individuals with Mild to Moderate Parkinson’s Disease. Front Aging Neurosci. 2015 Aug 10;7:151. doi: 10.3389/fnagi.2015.00151. eCollection 2015. 3 Lawrence, E. L., Dayanidhi, S., Fassola, I., Requejo, P., Leclercq, C., Winstein, C. J., & Valero-Cuevas, F. J. (2015). Outcome measures for hand function naturally reveal three latent domains in older adults: strength, coordinated upper extremity function, and sensorimotor processing. Frontiers in aging neuroscience, 7, 108.

« Back to 2019 International Congress

MDS Abstracts - https://www.mdsabstracts.org/abstract/botulinum-toxin-injections-reduce-the-symptoms-of-dystonic-tremor-and-improve-sensorimotor-function-for-hand-dexterity/