Study On Electromyography And Coherence Of Spasmodic Neck Surface

Background and AimsCervical dystonia(CD, Spasmodic torticollis) is the most common form among primary dystonia, characterized by involuntary contractions of cervical muscles leading to increases of head and neck movement, sustained or intermittent abnormal postures and impairment of sensory function. Its etiology is unclear and the pathophysiology involves multiple structures, including cortex, subcortex, brain stem and spinal cord. The clinical manifestation of cervical dystonia is complex and the diagnosis mainly depends on determination by physicians. The electromyograpic (EMG) feature of cervical dystonia is inconclusive, while researchers found low-frequency coherence between EMG activity of SCM and SPL among torticollis patients, which is not found in normal individuals, suggesting that EMG has potential in diagnosis. This research aims at:1. Investigating surface EMG features in cervical dystonia;2. Contracting muscular 4-7Hz coherence between torticollis patients and healthy people;3. Investigating diagnostic value of the coherence.MethodsIn total,41 patients with diagnosis of primary spasmodic torticollis were involved. Questionnaires were used for all subjects. EMG during abnormal posture and voluntary contraction is performed and recorded in 19 subjects who had never received botulinum toxin injection.8 healthy controls were involved. The coherence of EMG was assessed.Results1. The duration of disease is longer, while Tsui score and TWSTRS score were lower among patients with remission than those with progression (p<0.05). TWSTRS score was higher among patients with BTX-A treatment than those without BTX-A treatment.2. Fourteen patients were found to have tonic pattern of EMG activity while the remaining 5 patients have a mixture of tonic and bursting pattern complicated by tremor. EMG revealed more abnormal muscles than physical examination.No significant difference of the number of abnormal muscles was found among CD subtypes.3. Coherence analysis between 8 patients and 8 controls revealed 4-7Hz coherence during dystonic task. In comparison with the control group, the disease group had significant higher number of coherent muscle pairs (p<0.05), however, the median of coherent coefficient is significantly lower (p<0.05). No significant difference of numbers of coherent muscle pairs and coherent coefficient was found among each CD subtypes.Compared with the control group, the disease group had significant higher number of muscle pairs at 4-7Hz (p<0.05), while no significant difference between median of coherent coefficient was found during rotation task (dystonic direction and opposite-dystonic direction). No significant difference between the numbers of coherent muscle pairs was found during rotation task (dystonic direction and opposite-dystonic direction) in patients.4. Considering the examination of physicians as the reference standard, the sensitiviy of coherence analysis was 87.1%, and the specificity was 18.8%.Conclusion1. Cervical dystonia patients have a more pervasive and complicated EMG manifestation than physical examination. EMG shows tonic and bursting pattern, the latter often complicated by tremor. Co-contration、abnormal activities or no activity were observed among CD patients when they were doing voluntory exercises.2. In patients,4-7Hz coherence does exist among muscles, not limited to SCM and SPL. However, such coherence also exists among healthy people.also the specificity of coherence analysis is low. Therefore, it cannot be used for the diagnosis of spasmodic torticollis.