Application of SPECT/CT muscle imaging in determining the involved muscles in cervical dystonia

PURPOSE: This study examines the efficacy of single photon emission computed tomography/computed tomography (SPECT/CT) guided BoNT-A injections for alleviating motor and non-motor symptoms in cervical dystonia (CD) patients. It also assesses the accuracy of SPECT/CT muscle imaging in identifying responsible muscles and analyzes the quantitative significance of the SUVmax index. METHODS: A total of 102 patients diagnosed with primary cervical dystonia (CD) were recruited and assessed at baseline, as well as at 2, 4, 8, 12, and 24 weeks post-botulinum toxin A (BoNT-A) injection. Among these patients, 79 underwent SPECT/CT imaging (SPECT/CT group), and 23 did not (control group). Both groups received BoNT-A injections guided by EMG, and their symptom improvements were compared. In the SPECT/CT group, the distribution of responsible muscles and its correlation with clinical phenotypes were analyzed. Furthermore, in a subset of 51 CD patients, overall and mean SUVmax of responsible muscles were quantified, and their correlation with the severity of motor symptoms was analyzed. RESULTS: In both the Tsui and TWSTRS scales, the SPECT/CT group (n = 69) showed significantly higher overall improvement rates compared to the control group (n = 23), with statistically significant differences. In 79 CD patients, SPECT/CT imaging showed that common responsible muscles were the splenius capitis (SPCa), levator scapulae (Lev), splenius cervicis (SPCe), semispinalis capitis (SmCa), obliquus capitis inferior (OCI), and semispinalis cervicis (SSc). The deflection in CD patients was mainly influenced by the ipsilateral SPCa, SPCe, Lev, OCI, longissimus cervicis (LGc), and contralateral sternocleidomastoid muscle (SCM). In 51 CD patients, significant positive correlations were found between overall SUVmax of responsible muscles and motor symptom scores, as well as between the mean SUVmax of responsible muscles and motor symptom scores. CONCLUSION: SPECT/CT muscle imaging significantly improves motor symptoms in CD patients when used for BoNT-A injections. It effectively identifies responsible muscles, and its SUVmax value serves as an objective indicator of motor symptom severity. SPECT/CT shows promise as a valuable tool for diagnosing and treating CD.