Clinical Characteristics Of Sensory Tricks In Cervical Dystonia And The Relationship Between Sensory Tricks And Spatial Discrimination Threshold

Background:Cervical dystonia (CD) is one of the most common forms of focal dystonia. It manifests itself as abnormal movement and posture of neck and head caused by involuntary cervical muscle contraction. Sensory trick is a kind of trick or maneuver that enable patients to alleviate dystonic movements by touch some area of the head or neck, which is one of the most interesting phenomena of cervical dystonia. According to its dependence on force, sensory tricks can be divided into two different types, classical sensory trick (CST) and forcible sensory trick (FST). It is still unknown whether the laterality of sensory tricks relates to head deviation direction. The mechanism of sensory tricks has not been elucidated so far and little is known about the difference between CST and FST. Besides sensory tricks, increasing evidence suggests there are different kind of abnormality in sensory system of dystonia patients, like spatial and temporal discrimination. Is these sensory abnormalities relate to the effect of sensory tricks? Evidence so far seems controversy.Objective:Investigate clinical characteristics and relevant factors of sensory tricks in cervical dystonia and compare CST and FST. Investigate the relationship between sensory tricks and spatial discrimination threshold (SDT).Method:We use standard questionnaire and clinical evaluation to collect data from patients of cervical dystonia who visit neurology department of Peking Union Medical College Hospital for diagnosis and treatment. The collected data includes demographic characteristics, disease onset age, duration, factors aggravate or alleviate symptoms and the features of sensory tricks. We use TSUI score to evaluate the severity of the disease.We use J.V.P Domes to determine the SDT of healthy controls and patients. Compare the SDT of healthy controls, patients with complete relief by sensory tricks, patients with partial relief by sensory tricks and patients with no relief by sensory tricks.All data were input into a database and analyzed using statistical software IBM SPSS22.0.Result:We included240cervical dystonia patients into our study,75%of which had effective sensory tricks when investigated. One patient could have several kinds of sensory tricks. Most patients feel sensory tricks are less effective than botulinum toxin. Compared with patients who use FST, patients with CST are younger and had the disease at a younger age. They also have shorter disease duration and lower TSUI score (p<0.05). Most of the FST patients (55%) feel that sensory tricks ipsilateral to the head deviation are more effective. But there are some patients in both CST group and FST group who feel the effect of sensory tricks is equal on both side. In FST patients group, the effective rates of approach but no touch, imagine sensory tricks and lift both hands are lower than CST patient group (p<0.05). There is no significant difference of SDT between healthy controls and cervical dystonia patients, nor among patients with different effect of sensory tricks (p>0.05).Conclusion:Most of the cervical dystonia patients have sensory tricks. Patients with CST has less severe dystonia and the effect and duration of sensory tricks is better than FST patients. FST use not only counter pressure to relieve the symptoms. But compared with CST, FST is more dependent on tactile stimulation. The mechanism of sensory tricks is complex, it may act in a2-phase way. First make the head return to normal position and then maintain the normal position. The difference between FST and CST may be in the first phase. For patients with more severe dystonia, pressure is needed for the correction of head posture, so they need FST. We believe in the second phase, the mechanism of FST and CST are similar. Besides tactile stimulation, proprioceptive stimulation, movement stimulation, thermal stimulation, visual and auditory stimulation and even imagination of sensory tricks can alleviate dystonic symptoms. It means that sensory tricks may change the activation pattern of cortex and decrease abnormal intracortical facilitation by integrating different kind of sensory stimulation, and therefore alleviate dystonic symptoms. Sensory tricks may help the treatments of dystonia, but more research are needed.