Eccentric figure-eight coils for transcranial magnetic stimulation.

Previously we proposed an eccentric figure-eight coil that can cause threshold stimulation in the brain at lower driving currents. In this study, we performed numerical simulations and magnetic stimulations to healthy subjects for evaluating the advantages of the eccentric coil. The simulations were performed using a simplified spherical brain model and a realistic human brain model. We found that the eccentric coil required a driving current intensity of approximately 18% less than that required by the concentric coil to cause comparable eddy current densities within the brain. The eddy current localization of the eccentric coil was slightly higher than that of the concentric coil. A prototype eccentric coil was designed and fabricated. Instead of winding a wire around a bobbin, we cut eccentric-spiral slits on the insulator cases, and a wire was woven through the slits. The coils were used to deliver magnetic stimulation to healthy subjects; among our results, we found that the current slew rate corresponding to motor threshold values for the concentric and eccentric coils were 86 and 78 A/µs, respectively. The results indicate that the eccentric coil consistently requires a lower driving current to reach the motor threshold than the concentric coil. Future development of compact magnetic stimulators will enable the treatment of some intractable neurological diseases at home.

Validity, reliability, and assessment sensitivity of the Japanese version of the short-form McGill pain questionnaire 2 in Japanese patients with neuropathic and non-neuropathic pain.

OBJECTIVE: The objective of this study was to define the validity, reliability, and assessment sensitivity of the Japanese version of the Short-Form McGill Pain Questionnaire 2 (SF-MPQ-2-J). DESIGN: This is a cross-sectional study. PATIENTS AND METHODS: The original SF-MPQ-2 was translated into Japanese to create the SF-MPQ-2-J, and the cross-cultural equivalence of assessment tool for Japanese patients was validated. The reliability of the SF-MPQ-2-J was assessed using internal consistency, reliability coefficients (Cronbach's α), and reproducibility coefficients (intraclass correlation coefficient) obtained using 234 patients with chronic pain. SF-MPQ-2-J validity was assessed based on associations identified between total and subscale scores compared with other assessment methods. A confirmatory factor analysis (CFA) was also performed to test the theoretical structure of the SF-MPQ-2-J. RESULTS: The internal consistencies calculated included continuous pain, α=0.893; intermittent pain, α=0.875; predominantly neuropathic pain, α=0.917; affective descriptors, α=0.857; and total score, α=0.907. The reproducibility coefficients calculated included continuous pain, ρ=0.81; intermittent pain, ρ=0.78; predominantly neuropathic pain, ρ=0.85; affective descriptors, ρ=0.75; and total score, ρ=0.83. The CFA showed that the model fit of the readily interpretable subscales was acceptable, and the goodness of fit index value was 0.917. In addition, the mean predominantly neuropathic pain subscale score was found to be significantly higher for patients with neuropathic pain vs non-neuropathic pain. CONCLUSION: These findings suggest that the reliability and validity of the SF-MPQ-2-J are excellent, and the SF-MPQ-2-J represents a cross-cultural equivalent to SF-MPQ-2. Consequently, the latter is suitable for research and clinical use, and for discriminating neuropathic pain from non-neuropathic pain.

Coil positioning system for repetitive transcranial magnetic stimulation treatment by ToF camera ego-motion.

Repetitive transcranial magnetic stimulation (rTMS) is a non-invasive method for treating various neurological and psychiatric disorders. With the growing demands of neuropathic pain patients and their increasing numbers, rTMS treatment tools are becoming more necessary. rTMS uses electromagnetic induction to induce weak electric currents by rapidly changing the magnetic field. Targeting the electric current to a specific part of the brain is one treatment for pain relief. This paper focuses on treatment for neuropathic pain caused by a lesion or disease of the central or peripheral nervous system, including stroke, trauma, or surgery. However, the current style of rTMS treatment is still developing and is so technically specialized that only a limited number of hospitals and only a handful of specialists can provide this therapy. The existing rTMS systems use an optical markerbased 3D sensing technique that positions the stimulation coil to target the small region of interest in the brain through coregistration with pre-scanned MRI data. This system requires the patient to be immobilized on a bed. The optical markers for 3D sensing are placed on the patient's head to maintain accurate positioning. We propose a constraints-free, markerless rTMS system, which employs ego-motion, a computation technique to estimate relative 3D motion of a camera to what the camera sees. We use a ToF sensor as a camera, which is capable of capturing shape information from a single viewpoint instantly. The markerless target spot is based on the shape features of the patient's face. This paper shows the process of a prototype system and its potential for achieving an easy-to-handle system framework.

Electrical or repetitive transcranial magnetic stimulation of primary motor cortex for intractable neuropathic pain.

OBJECTIVE: To assess the pain-relieving effects of motor cortex electrical stimulation (MCS) and the predictive factors retrospectively. METHODS: Thirty-four patients with intractable neuropathic pain underwent MCS; 19 patients had cerebral lesions, and 15 had non-cerebral lesions. In selected 12 patients, test electrodes were implanted within the central sulcus and on the precentral gyrus. Twelve patients received both MCS and repetitive transcranial magnetic stimulation (rTMS) of the primary motor cortex. RESULTS: Pain reduction of >50% was observed in 12 of 32 (36%) patients with >12 months follow-ups (2 patients were excluded because of short follow-up). In 10 of the 12 patients who received test electrodes within the central sulcus and on the precentral gyrus, the optimal stimulation was MCS within the central sulcus. In 4 of these (40%) patients, positive effects were maintained at follow-ups. The pain reduction of rTMS significantly correlated with that of MCS during test stimulation. CONCLUSIONS: The test stimulation within the central sulcus was more effective than that of the precentral gyrus. In the selected patients, chronic stimulation within the central sulcus did not significantly improve long-term results. Repeated rTMS seems to be same effective as MCS.

Fabrication of a prototype magnetic stimulator equipped with eccentric spiral coils.

The development of compact magnetic stimulators will enable us to treat some intractable neurological diseases at one's home. In this study, we propose eccentric spiral coils which induce sufficient eddy currents in the brain at lower driving currents for the stimulator circuit. Numerical simulations based on the finite element method showed the advantages of the proposed design. A prototype coil and driving circuit were fabricated. The coil generated a magnetic field of 1.41 T at the maximum output level of stimulator.