Objective: The aim of this study is to compare the efficacy of selecting target muscles for botulinum toxin injection by abnormal movement pattern and by SPECT combined with abnormal movement pattern.

Background: Cervical dystonia (CD) is caused by involuntary and excessive contraction of cervical muscles which leads to abnormal movement and posture. Botulinum toxin injection has become the first line treatment for CD, the critical step which decides the treatment efficacy is to accurately identify dystonic muscles. At present, dystonic muscles are selected by patients’ abnormal movement pattern. However, most patients have a combination of various patterns, and the same pattern may be caused by contraction of different muscles. SPECT imaging uses 99mTc-MIBI as a contrast agent, which can reveal abnormal contraction of the muscle. However, SPECT has not been reported to guide the treatment of CD.

Methods: Forty patients with idiopathic CD were enrolled. These patients had not received botulinum toxin injection for last 3 months.The first group: dystonic muscles were screened based on cervical dystonia pattern (n1=20). The second group: we analyzed cervical muscles with increased uptake of 99mTc-MIBI in cervical SPECT, the SPECT results combined with cervical dystonia pattern were used to determine dystonic muscles (n2=20). SPSS20.0 software was used to compare the results between the two groups after botulinum toxin injection. The TWSTRS score reduction rate and Tsui score reduction rate at the second week, the first month, the third month and the sixth month were compared.

Results: The number of botulinum toxin reinjection in 6 months was significantly higher in the first group than in the second group (13: 4). The interval between the first and the second injection of the second group was significantly longer than the first group (p < 0.05). There was no significant difference between TWSTRS score reduction rate and Tsui score reduction rate in the second week and the first month after treatment, p> 0.05. At the third month, TWSTRS score reduction rate and Tsui score reduction rate of the second group was significantly higher than the first group, p <0.05. At the 6th month, although the number of follow-up in was decreased in both groups because of repeat injection (n1 = 5: n2 = 14), the TWSTRS reduction rate and the Tsui reduction rate in the second group were significantly higher than the first group , P <0.05.

Conclusions: SPECT imaging can more accurately select the dystonic muscles and thus greatly improve the efficiency and remission rate of botulinum toxin treatment.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/the-clinical-value-of-spect-in-identifying-dystonic-muscles-of-patients-with-cervical-dystonia/