Normal parameters for diagnostic transcranial magnetic stimulation using a parabolic coil with biphasic pulse stimulation

Abstract

Background TMS is being used to aid in the diagnosis of central nervous system (CNS) illnesses. It is useful in planning rehabilitation programs and setting appropriate goals for patients. We used a parabolic coil with biphasic pulse stimulation to find normal values for diagnostic TMS parameters. Objectives 1. To determine the normal motor threshold (MT), motor evoked potentials (MEP), central motor conduction time (CMCT), intracortical facilitation (ICF), short-interval intracortical inhibition (SICI), and silent period (SP) values. 2. To measure the MEP latencies of abductor pollicis brevis (APB) and extensor digitorum brevis (EDB) at various ages, heights, and arm and leg lengths. Study design Descriptive Study. Setting Department of Rehabilitation Medicine, Chiang Mai University, Thailand. Subjects Forty-eight healthy participants volunteered for the study. Methods All participants received a single diagnostic TMS using a parabolic coil with biphasic pulse stimulation on the left primary motor cortex (M1). All parameters: MT, MEP, CMCT, ICF, SICI, and SP were recorded through surface EMGs at the right APB and EDB. Outcome parameters were reported by the mean and standard deviation (SD) or median and interquartile range (IQR), according to data distribution. MEP latencies of APB and EDB were also measured at various ages, heights, and arm and leg lengths. Results APB-MEP latencies at 120% and 140% MT were 21.77 ± 1.47 and 21.17 ± 1.44 ms. APB-CMCT at 120% and 140% MT were 7.81 ± 1.32 and 7.19 ± 1.21 ms. APB-MEP amplitudes at 120% and 140% MT were 1.04 (0.80–1.68) and 2.24 (1.47–3.52) mV. EDB-MEP latencies at 120% and 140% MT were 37.14 ± 2.85 and 36.46 ± 2.53 ms. EDB-CMCT at 120% and 140% MT were 14.33 ± 2.50 and 13.63 ± 2.57 ms. EDB-MEP amplitudes at 120% and 140% MT were 0.60 (0.38–0.98) and 0.95 (0.69–1.55) mV. ICF amplitudes of APB and EDB were 2.26 (1.61–3.49) and 1.26 (0.88–1.98) mV. SICI amplitudes of APB and EDB were 0.21 (0.13–0.51) and 0.18 (0.09–0.29) mV. MEP latencies of APB at 120% and 140% MT were different between heights < 160 cm and ≥ 160 cm (p < 0.001 and p < 0.001) and different between arm lengths < 65 and ≥ 65 cm (p = 0.022 and p = 0.002). Conclusion We established diagnostic TMS measurements using a parabolic coil with a biphasic pulse configuration. EDB has a higher MT than APB. The 140/120 MEP ratio of APB and EDB is two-fold. The optimal MEP recording for APB is 120%, whereas EDB is 140% of MT. CMCT by the F-wave is more convenient and tolerable for patients. ICF provides a twofold increase in MEP amplitude. SICI provides a ¼-fold of MEP amplitude. SP from APB and EDB are 121.58 ± 21.50 and 181.01 ± 40.99 ms, respectively. Height and MEP latencies have a modest relationship, whereas height and arm length share a strong positive correlation.

Intermittent theta-burst stimulation combined with transcranial direct current stimulation once weekly for treatment-resistant depression: a case report

“…They found a decrease in PHQ-9 score from a mean score of 18.3 to 9.6 [ 29 ]. The clinical follow-up with a PHQ-9 score was congruent with the diagnostic TMS, which showed a more positive direction in hypoexcitability from the dominant hemisphere [ 14 ].…”

“…Before treatment, the diagnostic TMS demonstrated marked hypoexcitability of the left hemisphere due to a significant drop in motor-evoked potential [(MEP) 0.64 mV] and intracortical facilitation [(ICF) 1.43 mV] at 120% of motor threshold (MT), decreased short intracortical inhibition [(SICI) 1.02 mV], and a prolonged silent period (195 ms). Details of the normal diagnostic TMS parameters were described in our prior study [ 14 ]. Her PHQ-9 score was 23 out of 27, indicating severe depression.…”

Hebbian plasticity induced by temporally coincident BCI enhances post-stroke motor recovery

“…While sample size is an important consideration, given the small number of patients for whom MEP data were available, the approach taken to evaluating TMS should also be considered. C4 is considered to correspond with the hand area of the primary motor cortex 65,66 , and stimulation of C3/C4, with MEP measurement, is a standard evaluation approach [67][68][69] . While the precise, individual location of the motor hotspot corresponding to a particular muscle varies 66,70 , particularly after stroke 71 , measuring according to a fixed anatomical location allows a direct within-subject assessment of a change in MEP amplitude between time points.…”

Effectiveness and brain mechanism of multi-target transcranial alternating current stimulation (tACS) on motor learning in stroke patients: study protocol for a randomized controlled trial

“…Paired pulse TMS (pTMS, Xiang Yu Medical; China) will be used to measure short intracortical inhibition (SICI) and intracortical facilitation (ICF), both of which are important indicators for evaluating the plasticity of the cerebral cortex. Building upon the preceding procedures, SICI and ICF entail a stimulation at 80% of the resting threshold (RT), a second stimulation at 120% of RT, and an interstimulus interval (ISI) of 3 ms and 12 ms, respectively [ 38 ]. Similar to the MEP assessment, each parameter will be subjected to five stimulations to calculate the average value.…”