Elucidation Of The Mechanism Underlying Impaired Sensorimotor Gating In Patients With Primary Blepharospasm Using Prepulse Inhibition

Objective:This prospective study aimed to analyze the prepulse inhibition（PPI）impairment of the blink reflex in patients with primary blepharospasm（BSP）to investigate the neurophysiological mechanisms of impaired sensorimotor gating in BSP patients and to provide an objective basis for identifying biological markers,providing early diagnosis,guiding treatment,and assessing prognosis.Methods:30 BSP patients（17 patients with sensory tricks and 13 patients without sensory tricks）attending the Movement Disorders Clinic at The First Affiliated Hospital of Dalian Medical University from November 2021 to August 2022 were included consecutively,while 20 healthy volunteers randomly matched for age and gender of BSP patients were recruited as the control group.A structured interview was conducted with all subjects to obtain clinical data on their medical history,family history,and current medication and to record contraceptive use and menstrual cycle in females.In addition,all BSP patients completed the Jankovic Rating Scale（JRS）to assess the motor symptom severity.Two types of neurophysiological assessments were performed on the subjects using an electromyography（Oxford,UK,10-channel）.1.Baseline trials:Baseline blink reflexes were obtained by stimulating the subject’s right supraorbital nerve with an electrical stimulation intensity 10 times the sensory threshold;2.Prepulse trials:Weaker prepulse stimulation was applied to the subject’s right index finger at interstimulus intervals（ISIs）of 120 ms,200 ms and 300 ms before the supraorbital nerve stimulation using an electrical stimulation intensity 2 times the sensory threshold.In this way,the blink reflex curve after inhibition was acquired.Determined the ipsilateral R₁and R₂of each blink reflex as well as the contralateral R_2c.The areas under the curve were used to represent the magnitude of the R₂and R_2cresponses.For PPI analysis,the percentage change in R₂area after the baseline trials and prepulse trials was represented as the PPI size.Compared the PPI size between case and control groups,BSP patients with sensory tricks and those without sensory tricks.Analyzed the correlations of PPI with disease duration and JRS score.Compared within-group differences in ipsilateral R₁latency and peak-to-peak amplitude,as well as bilateral R₂latencies and areas at baseline and prepulse trials in the case and control groups,respectively.Compared inter-group differences in ipsilateral R₁latency and peak-to-peak amplitude,as well as bilateral R₂latencies and areas between the case and control groups at baseline and prepulse trials.Finally,explored the variability of PPI in the control group at different ISIs.Results:1.At ISI of 120 ms,200 ms and 300 ms,the PPI in the control group was 37.4%,49.8%and 40.5%,respectively,while the PPI in the case group was 13.3%,16.8%and13.1%,respectively,that is,the PPI in the case group was smaller than that in the control group,and the difference was statistically significant（p<0.01）.2.At ISI of 120 ms,200 ms and 300 ms,the PPI was 19.5%,21.4%and 16.9%in BSP patients with sensory tricks and 5.2%,10.8%and 8.1%in those without sensory tricks,respectively,that is,the PPI was greater in patients with sensory tricks compared to those without sensory tricks,and the difference was statistically significant（p<0.05）.3.Disease duration and JRS scores in BSP patients did not show a significant correlation with PPI.4.In the control group,R₂and R_2clatencies were longer at the prepulse trials compared to the baseline trials（p<0.01）,and the R₁peak-to-peak amplitude was higher at ISI of 120 ms（p<0.05）.However,in the case group,prepulse stimulation had no significant effect on R₂and R2_clatencies as well as R₁peak-to-peak amplitude.5.Although there was no statistical difference,the PPI of the control groupappeared to be greatest at 200 ms,with 49.8%.Conclusion:1.Compared with controls,BSP patients had impaired PPI.2.PPI was less impaired in BSP patients with sensory tricks compared to those without sensory tricks.3.PPI did not correlate with the motor symptom severity and disease duration.4.Compared to healthy subjects,the prolonging effect of prepulse stimulation on R₂and R_2clatencies and the increasing effect of prepulse stimulation on R₁peak-to-peak amplitude were absent in BSP patients.5.PPI in healthy Chinese population appeared to be more pronounced at ISI of 200ms.