Objective: To investigate if cervical dystonia (CD) patients show structural grey matter changes and if these changes may be associated with previous botulinum neurotoxin (BoNT) treatment.

Background: CD is not characterized by overt, but subtle (heterogeneous) structural brain changes using newer MRI techniques. Whether these changes are disease- or therapy-specific is not known.

Method: We examined 2 groups of 11 female CD patients each, one without previous (BoNT-naïve; age 53±8 years (y); disease duration 2±3y) and one with previous BoNT injections (age 56±11y; disease duration 17±14y, BoNT-treatment for 10±7y). Both patient groups underwent structural 3 Tesla MRI on 3 occasions: Before (BoNT-naïve group) and 12-14 weeks after their last BoNT treatment (BoNT-treated), respectively, 4 weeks and ~12 weeks following BoNT therapy. Furthermore 11 age-matched neurologically healthy female controls were included (age 58±10 y). Morphometric analyses (VBM) were performed using SPM12 and the CAT12 Toolbox with non-parametric and permutation-based tests (TFCE; dbm.neuro.uni-jena.de).

Results: The 3 groups did not differ with respect to cognitive test performance (MoCA: BoNT-naïve 27.0±2.6 vs. BoNT-treated 25.8±3.2 vs. controls 27.7±2.2; p=0.26). No significant differences were found between the 2 patients groups with respect to CD severity (TWSTRS 39.8±11.8 vs. 34.0±7.9; p=0.10). VBM showed significant group differences FWETFCE<0.05) with smaller grey matter volume (GMV) in frontotemporal regions in the 2 CD groups compared to controls. However, changes were much more widespread in the BoNT-treated compared to the BoNT-naïve group and depended from longer BoNT treatment (or disease) duration. Both CD groups strongly differed in bilateral mesiotemporal GMV (BoNT-naïve>BoNT-treated). No short-term effects of BoNT were present.

Conclusion: This study shows widespread structural brain changes in CD patients compared to controls. Our data suggest that frontotemporal changes may be associated with the dystonic phenotype, however, the observation of bilateral mesiotemporal GMV reduction in BoNT-treated vs. BoNT-naïve CD patients indicates distinct central long-term effects of continuous BoNT therapy. Alternatively, disease duration may be responsible for these mesiotemporal changes.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/central-effects-of-botulinum-neurotoxin-injections-in-cervical-dystonia-a-longitudinal-structural-mri-study/