Localization of dystonic muscles using 18F-FDG PET/CT in idiopathic cervical dystonia

Chemodenervation with botulinum toxin (BT) is regarded as a first-line treatment for idiopathic cervical dystonia (ICD), sometimes referred to as spasmodic torticollis. Moreover, because effective treatment involves the injection of BT into most dystonic muscles, the accurate localization of dystonic muscles is clinically important. In this preliminary study, we investigated whether 18F-FDG PET/CT is useful for localizing dystonic cervical muscles in ICD by comparing disease severity after and before BT injection into muscles determined to be hypermetabolic by PET/CT. Six consecutive patients (all males; age 37 16 y) underwent 18F-FDG PET/CT once (n = 4) or twice (n = 2) in a supine (n = 5) or sitting position (n = 3) during the 18F-FDG uptake period. Dystonic muscles suitable for BT injection therapy were defined as those showing diffusely increased 18F-FDG uptake. To evaluate response to BT injection, the Tsui scale and the Toronto Western Spasmodic Torticollis Rating Scale (TWSTRS) were applied. On PET/CT, hypermetabolic cervical muscles were identified in all 6 patients (3 in a supine position and 3 in a sitting position during 18F-FDG uptake periods). In 2 patients who underwent PET/CT in a supine and in a sitting position during 18F-FDG uptake, abnormal hypermetabolic muscles were observed only by PET/CT in a sitting position with patients heads and necks in the assumed abnormal involuntary posture. Symptoms were significantly improved, according to the Tsui (10.0 2.9 to 1.8 1.3, 82% reduction) and TWSTRS scales (severity: 21.3 2.1 to 5.8 5.3, 73% reduction; disability: 19.8 1.9 to 3.8 3.8, 81 % reduction) in all 4 patients who underwent BT injection therapy guided by PET/CT and who were clinically follow-up. 18F-FDG PET/CT is potentially useful for identifying dystonic cervical muscles in patients with ICD