Evaluation of atrophy after botulinum toxin injection in cervical dystonia by MRI

Objectives: Cervical dystonia (CD) is one of the most common forms of dystonia seen clinically, Botulinum neurotoxin type A (BoNT) is known as the first-line therapy for CD. One of the most critical side effects of chronic exposure to BoNT is developing muscle atrophy which causes cosmetic issues and future injection difficulty. In this study, we examined the degree of atrophy caused by botulinum toxin injection, as the most effective treatment of CD, and the factors affecting it to reduce atrophy. Methods: Patients underwent treatment by injecting standard doses of BoNT for 12 months. Soft-tissue cervical MRI was performed for seven patients before treatment and 12 months later. Sternocleidomastoid and splenius capitis in the transverse cut in T1 MRI view were measured in MRIs for each patient, and muscle atrophy volume was calculated. Results: Two patients were male, five were female, and the mean age was 40 +/- 12.76 years. The amount of atrophy increased significantly with increasing injection dose and frequency. Muscular atrophy was significantly higher in people older than 50 years, but gender and body mass index (BMI) had no significant effect. Conclusion: Muscular atrophy is more likely in older patients, those treated with higher doses of BoNT, and those who received more frequent injections.