Monophasic-Quadripulse Theta Burst Magnetic Stimulation for Motor Palsy Functional Evaluation After Intracerebral Hemorrhage

Abstract

Transcranial magnetic stimulation (TMS) is commonly employed for diagnostic and therapeutic purposes to enhance recovery following brain injury, such as stroke or intracerebral hemorrhage (ICH). Single-pulse TMS, most commonly used for diagnostic purposes and with motor evoked potential (MEP) recordings, is not suitable for clinical use in patients with severe motor paresis. To overcome this problem, we developed a quadripulse theta burst transcranial magnetic stimulation (QTS) device that combines the output from 16 stimulators to deliver a train of 16 monophasic magnetic pulses through a single coil. High-frequency theta rhythm magnetic bursts (bursts of four monophasic pulses, at 500 Hz, i.e., with a 2-ms interpulse interval, repeated at 5 Hz) were generated via a set of 16 separate magnetic stimulators connected to a specially designed combination module. No adverse effects or electroencephalogram (EEGs) abnormalities were identified during or after the recordings. MEP amplification in the QTS during four-burst theta rhythm stimulations produced four independent MEPs 20 ms after each burst onset maximizing the final third or fourth burst, which exhibited significantly greater amplitude than those resulting from a single burst or pulse. Motor functional palsy grades after ICH and QTS-MEP parameters and resting motor threshold (RMT) and amplitudes were significantly correlated (r = −0.83/−0.81 and 0.89/0.87; R2 = 0.69/0.66 and 0.79/0.76, p < 0.001; anterior/posterior-stimulus polarity, respectively). In conclusion, QTS-MEPs enabled a linear functional evaluation in patients with various degrees of motor paresis. However, the benefits, safety, and limitations of this device should be further explored in future studies.

Monophasic-quadri-burst stimulation robustly activates bilateral swallowing motor cortices

“…These correlations were higher for amplitude than for RMTs, and linear correlations were observed for mylohyoid-MEPs after QBS5 alone. Although these correlations were relatively weak, they are clearly compatible with previous QTS results for FDI-MEPs ( Fujiki et al, 2022 ). Mylohyoid MEP facilitations after QBS5 conditioning and QTS amplification for FDI MEP relies on fundamentally different neuromodulations, this supports the hypothesis that presynaptic projections to pyramidal cells in the swallowing-related hyoid muscle group are less frequent than in the hand muscles and therefore less accessible to transsynaptic stimulation ( Guggisberg et al, 2001 ).…”

“…We analyzed data from the same 65 participants included in our previous study, which demonstrated the superiority of monophasic quadripulse theta-burst magnetic stimulation (QTS) in patients with hand motor paralysis following left hemisphere intracerebral hemorrhage (ICH) ( Fujiki et al, 2022 ). The original study included a control group of 10 healthy, right-handed men (age range: 40–68 years; mean ± SD: 58.5 ± 10.8 years) without any contraindications to TMS, as well as 65 patients with hypertension who had experienced putaminal ICH (5 women, 60 men; age range: 55–80 years; mean ± SD: 68.9 ± 11.8 years).…”

“…Control studies for healthy participants [under electroencephalographic (EEGs) monitoring for detection of subclinical abnormalities] were performed as described in our previous study ( Figure 1B ; Fujiki et al, 2022 ) to test three different configurations of the posterior- anterior directed induced current flow (i.e., monophasic single pulse [SP], 500 Hz [i.e., 2-ms interstimulus interval (ISI)-quadripulse single train stimulation (QPS)] and QBS5) were validated in both hemisphere in each modality. A 70-mm figure-8 coil was used to deliver magnetic pulses at 1.2 times the resting motor threshold (RMT) for MEP recording.…”

“…Monophasic magnetic flux data recorded using ossiloscope and pickup coil was originated from our previous publication ( Fujiki et al, 2022 ). (B) SP, QPS, or QBS5 was applied to the hand and mylohyoid muscle area of the left motor cortex with a PA directed monophasic magnetic QBS-induced MEPs device system, including a set of 16 separate magnetic stimulators (Magstim, 2002; The Magstim Co., Ltd., Wales, UK) connected with a specially designed combining module ( Fujiki et al, 2022 ; patent number 7189594). This device combines the outputs from the 16 stimulators to deliver a train of 16 monophasic magnetic pulses through a single coil.…”

“…To address this issue, we developed a system for measuring MEPs that relies on monophasic quadripulse theta-burst magnetic stimulation (QTS). In this system, the outputs of 16 stimulators ( Magstim 200 2 is a product by the Magstim Co., Ltd.) are combined using a specially designed module, following which four sets of four-monophasic magnetic pulses are transmitted via a single coil ( Fujiki et al, 2022 ; patent number 7189594). We applied a system for MEP conditioning that relies on a 5 ms interval-monophasic quadripulse magnetic stimulation (QPS5) paradigm ( Hamada et al, 2008 ), which is known to induce long-term potentiation (LTP) in the human hand motor cortex.…”