Botox for Cervical Dystonia Following EMG Mapping

The most common type of primary late-onset dystonia is cervical dystonia. Botulinum toxin A (BTX-A) injections are a safe and effective treatment for cervical dystonia in a majority of patients, however, a significant minority of patients (between 15 and 25%) have a suboptimal response to Botulinum toxin therapy. It is unclear why some patients do not respond maximally to neurotoxin therapy.

Studies using needle electromyographic "mapping" in the evaluation of cervical dystonia have revealed that clinical examination alone is insufficient for determining which muscles contribute to the dystonic movement. When compared to needle electromyography (EMG) "mapping studies", experienced movement disorders specialists correctly identify only 59% of active muscles and believe that 25% of muscles which upon EMG evaluation are found to be quiescent, are involved in the dystonia. The selection of incorrect muscles for injection of Botulinum toxin may explain why some patients have a sub-optimal response.

This study seeks to measure outcomes when the muscles involved in dystonia are identified using "mapping" via an 8-12 channel EMG. In the proposed study, the most involved/active dystonic muscles will be correctly identified through simultaneous 8-12 channel mapping resulting in a more informed injection strategy, which may improve response to Botulinum toxin A treatment as compared to single lead EMG based injections. This study changes routine clinical care only by adding the step of studying the muscles of the neck with simultaneous EMG mapping to allow a more objective injection strategy.

Inclusion criteria

• Male or female subjects, 18 to 75 years of age.
• Ability to follow study instructions and complete all required visits.
• Subject meets diagnostic criteria for idiopathic primary cervical dystonia.
• Subject has at least moderate severity Cervical Dystonia, with a baseline rating of at least 30 on the total TWSTRS and at least 15 on the TWSTRS motor severity subsection.
• Patients have had a suboptimal response to 2 previous Botulinum toxin injections at an outside facility.
• Patients will not have received Botulinum toxin within 16 weeks of the start of the study.
• In order to not confound the clinical response to BTX-A injections, all patients enrolled must have been on a stable medication regimen for 30 days. If they are not on medication at the initiation of the study, they will not be started on medication. Patients must be on the same medication regimen through the entire study including assessment of both single lead EMG based injections and "mapping" based injections. Medications cannot be stopped during the study to avoid confounding the clinical response to BTX-A.

Exclusion criteria

• Known allergy or sensitivity to any of the components in BTX-A.
• Uncontrolled clinically significant medical condition other than the condition under evaluation
• Females with a positive pregnancy test, or who are breast-feeding, planning a pregnancy during the study, who think that they may be pregnant at the start of the study or females of childbearing potential who are unable or unwilling to use a reliable form of contraception during the study.
• Participation in another medication or device study or within 3 months of enrollment in this study.
• Patients know to have a positive frontalis test or have previously tested positive for the presence of BTX-A antibodies will be excluded.
• Any known evidence of cervical contractures or significant spinal deformity.