Abstract
Objectives T2 relaxation times (T2RT) of muscles increase with physical exercise, however T2RT has not been studied in dystonic muscles with are in a state of constant activity. Major muscles involved in cervical dystonia (CD) include splenius capitis, semispinalis capitis, levator scapulae, sternocleidomastoid and trapezius which are also prime targets for botulinum toxin treatment. This study analysed the T2RTs in key neck muscles in CD, and compared them with normal subjects.
Methods 23 CD subjects underwent MRI and clinical assessment just prior to their next cycle of botulinum toxin treatment. 3 patients were excluded from data analysis due to significant muscle atrophy. Using T2 images, two circular regions of interest (ROIs) were drawn in two mutually exclusive regions within neck muscle fibres at two different levels and the values averaged. ROI values were translated into T2RTs. T2RTs were compared with the Toronto Western Spasmodic Torticollis Rating Scale (TWSTRS) and EMG activity score.
Results CD subjects showed higher T2RTs in different neck muscles compared to normal subjects. T2RTs correlated with TWSTRS scores, but not EMG scores. When clinically separated into simple torticollis and complex CD, there were no significant differences in neck muscle T2RTs.
Conclusion T2RT may be helpful in distinguishing dystonic vs normal neck muscles, allowing more accurate targeting of muscle groups for botulinum toxin treatment. T2RT may be supportive in the diagnosis of cervical dystonia. Future studies could compare qualitative EMG scoring and vs quantitative T2RTs in the identification and assessment of dystonic neck muscles.
