Effect of Botulinum Toxin Therapy on the Sensorimotor Feedback Loop in Cervical Dystonia (IN6-1.009)

Abstract

Objective: To study the effects of botulinum toxin on intracortical inhibition and somatosensory organization. Background The cardinal manifestations of dystonia may be explained by excessive gain through a sensorimotor loop. Expanded overlapped receptor fields induce sustained, uncontrolled motor activity with co-contraction and overflow movements. There is a decreased cortical and spinal inhibition in dystonic patients. Increased motor and supplemental cortical excitability was demonstrated in trans-cranial magnetic stimulation studies. Somatosensory evoked potential studies have shown an increased sensory cortical excitability. Our group recently found synchronous (Coherent) neuronal oscillations to be higher in Epilepsy patients compared to controls which correlated with epileptogenic focus. The current study evaluated the alteration of neuroplasticity in dystonic patients treated with botulinum treatment (BTx). Design/Methods: Six patients with cervical dystonia were studied using MEG. Two MEG scans were obtained, one just prior to the Btx injections, and the second scan when patient felt maximum relief (at approximately 4 weeks). Tsui Torticollis Rating Scale (TTRS) was employed to evaluate treatment response. A whole head Neuromagnetometer (148 channel, Magnus 2500 system) was used. Spontaneous resting brain activity for Coherence (C) analysis was obtained. Somatosensory evoked field scans (SES) were obtained through sensory evoked responses to pressure tapping of the second digit. Results: All patients achieved significant improvement which corresponds to a reduction in their TTRS. Average pretreatment coherent rest values of 0.42 + 0.09 decreased to 0.38 + 0.07 after Btx. These were much higher than the resting state coherent values of normal controls of 0.17 +/-0.09 (p Conclusions: 1. Reduced Coherence values for resting brain activity indicate Btx restores intra-cortical inhibition. 2. Btx induced SES alteration modifies somatosensory processing contributing to the near normalization of dystonic posturing. Supported by: Research support from Allergan for the project : Effects of Botulinum on the Afferent Input Modulation of Neuronal Circuits Involved in Cervical Dystonia. Disclosure: Dr. Sripathi has nothing to disclose. Dr. Grover has nothing to disclose. Dr. Sidiropoulos has nothing to disclose. Dr. Bowyer has nothing to disclose.