Therapeutic Efficacy and Prediction of 18F-FDG PET/CT-Assisted Botulinum Toxin Therapy in Patients With Idiopathic Cervical Dystonia.

[PURPOSE] This study aimed to investigate the therapeutic efficacy of 18F-FDG PET/CT-assisted botulinum toxin (BTX) injection therapy and predictive PET findings in relation to a good response in patients with idiopathic cervical dystonia (ICD).

[MATERIALS AND METHODS] A total of 78 patients was enrolled from November 2007 to July 2018. The Toronto Western Spasmodic Torticollis Rating Scale (TWSTRS) score was determined at baseline and 4 weeks after BTX injection guided by electromyography and PET/CT. The number of hypermetabolic muscles, the highest SUVmax among hypermetabolic muscles, and the total SUVmax of hypermetabolic muscles were evaluated as pretreatment PET parameters. A good response was defined as a reduction rate ≥30% and a point decrease ≥15 of the TWSTRS total score.

[RESULTS] Half of the subjects showed a good response. Good responders had significantly higher baseline TWSTRS scores than poor responders (total score, P < 0.001; severity, P < 0.001; disability, P < 0.001; pain, P = 0.026). Good responders also had significantly higher numbers of hypermetabolic muscles and BTX-injected hypermetabolic muscles (P < 0.001, both). In multivariable analysis, the baseline TWSTRS disability subscale score and the number of BTX-injected hypermetabolic muscles were significant predictors for good response (P = 0.001 and P = 0.028). The aforementioned 3 PET parameters were positively correlated with the baseline TWSTRS scores. In addition, PET/CT well detected dystonic deep cervical muscles.

[CONCLUSIONS] FDG PET/CT-assisted BTX injection therapy showed good therapeutic efficacy in ICD patients. The numbers of hypermetabolic cervical muscles and BTX-injected hypermetabolic muscles may be helpful in predicting a good response.