3. An effect of video-assisted motor imagery on F waves during motor imagery after volitional relaxation

Abstract

Listen

Translate article

s of the 41th Annual Meeting of Japanese Society of Clinical Neurophysiology, Shizuoka, Japan, November 10–12, 2011 Akio Kimura , Koichi Hirata b,⇑ Koishikawa Building 4F, 5-3-13 Otsuka, Bunkyo-ku, Tokyo 112-0012, Japan, Department of Neurology, Dokkyo Medical University, 880 Kitakobayashi, Mibu, Shimotsuga, Tochigi 321-0293, Japan 1. Altered axonal excitability and ‘‘split hand’’ in amyotrophic lateral sclerosis—Kazumoto Shibuya, Kazuaki Kanai, Sonoko Misawa, Saiko Nasu, Yukari Sekiguchi, Satsuki Mitsuma, Minako Beppu, Yumi Fujimaki, Shigeki Ohmori, Satoshi Kuwabara (Department of Neurology, Chiba University, Chiba, Japan) In amyotrophic lateral sclerosis (ALS), muscle wasting preferentially affects abductor pollicis brevis (APB) compared with abductor digit minimi (ADM). This phenomenon is termed ‘split hand’ and considered to be specific to ALS. To elucidate the pathophysiology of ‘split hand’, we prospectively studied excitability properties at the wrist in the median-APB and ulnar-ADM motor axons in 19 ALS patients and 16 normal controls. In patients with ALS, there were longer strength duration time constant, larger threshold changes in depolarizing threshold electrotonus, greater supernormality, and greater late subnormality both in the median-APB and ulnar-ADM motor axons, compared with normal controls. The above findings suggest motor axonal hyperexcitability in ALS and the extent of excitability changes were more remarkable in the median-APB axons than in the ulnar-ADM axons. Differences in motor axonal excitability could lead to the different extent of glutamate excitotoxicity or metabolic demand spinal motoneurons. Excessive membrane excitability, which is prominent in the median-APB axons, could facilitate motor neuronal loss and this might correlate pathophysiology of ‘split hand’ in ALS. doi:10.1016/j.clinph.2012.02.002 2. Neuromagnetic evoked field measurements in the lumbar spine after tibial nerve stimulation at the popliteal fossa—Dai Ukegawa, Shigenori Kawabata, Shoji Tomizawa, Senichi Ishii, Kyohei Sakaki, Hiroyuki Inose, Toshitaka Yoshii, Tsuyoshi Kato, Atsushi Okawa (Tokyo Medical and Dental University, Tokyo, Japan) We previously reported successfully measuring neuromagnetic evoked fields in the lumbar spine (Cauda Equina Action Fields; CEAFs) of healthy subjects after tibial nerve stimulation at the ankle. The objective of this study was to measure larger CEAFs after tibial nerve stimulation at the level of the popliteal fossa in 3 healthy subjects. Neuromagnetic fields were measured over the surface of the lower back with a Superconducting Quantum Interference Device (SQUID) fluxmeter. A spatial filter method (UGMN) was applied to the magnetic field data obtained. Neuromagnetic fields propagating from the intervertebral foramina into the spinal canal were measured in each healthy subject by stimulation at each site. The magnetic fields were approximately 4 times larger after electrostimulation at the level of the popliteal fossa than at the ankle. The latencies of the magnetic fields corresponded to the physiological nerve conduction velocity. Isomagnetic field maps of the CEAFs showed a quadrupolar pattern propagating in a caudal to cranial direction along the lumbar spine in response to stimulation at both sites. We succeeded in measuring large CEAFs in healthy subjects by using the new stimulation method. Improving this method may allow diagnostic testing of spinal nerve function by a completely non-invasive technique. doi:10.1016/j.clinph.2012.02.003 3. An effect of video-assisted motor imagery on F waves during motor imagery after volitional relaxation—Shinichirou Taniguchi, Toshikazu Tani, Kenji Ishida, Takahiro Ushida, Tatsunori Ikemoto, Noritsuna Nakajima, Nobuaki Tadokoro, Takanori Saito, Jun Kimura (Kansai Medical University, Takii Hospital, Osaka, Japan) To investigate the effect of video-assisted motor imagery during volitional relaxation, we recorded 100 F waves from APB, during continuous motor imagery of thumb abduction, before and after the relaxation in 9 healthy volunteers. In experiment (1), the subjects were immobilized with bandage and instructed to relax for 3 h. In experiment (2) and (3), the subjects were repeated the same sequence but instructed to periodically image muscle contraction, without any aids in experiment (2) or with the aid of video in experiment (3), during the 3-h relaxation period. F-wave persistence and baseline-to-peak amplitude were statistically analyzed (ANOVA). Results: In experiment (1), both F-wave persistence and amplitude (mean) declined from the baseline value of (50.2% and 140.5 lV) to (38.7% and 92.5 lV) after volitional relaxation, showing a statistical difference (P < 0.05). The corresponding sequence consisted of ⇑ Corresponding author. Tel.: +81 282 87 2152; fax: +81 282 86 5884. E-mail address: hirata@dokkyomed.ac.jp (K. Hirata). Clinical Neurophysiology 123 (2012) e87–e100