Transcranial motor evoked potentials (Tc-MEPs) are a valuable intraoperative modality in spinal and spinal cord surgery for predicting postoperative paralysis. Arm Tc-MEPs are generally easily induced, but leg Tc-MEPs have a lower induction rate, and patients in whom leg Tc-MEPs cannot be induced are often encountered in spinal and spinal cord surgery in particular. Different hospitals use different cranial stimulation sites for leg Tc-MEPs, and an investigation of the optimal stimulation site will be helpful for preventing postoperative paralysis. In this study, the optimal stimulation site in the temporal direction was investigated, with the objective of improving the leg Tc-MEP induction rate. The subjects were 200 patients undergoing spinal cord or spinal surgery. The stimulation sites were determined by measuring lateral distances of 3 cm, 5 cm, 7 cm, 9 cm, and 11 cm from the vertex (Cz) and conducting stimulation at the five points 2 cm anterior to each of these points. The results showed that the induction rate was highest and the stimulus threshold was lowest at the stimulation site 2 cm anterior to the point 7 cm lateral to the vertex. A similar level of induction was also possible at the stimulation site 2 cm anterior to the point 9 cm lateral to the vertex, but the induction rates were significantly lower, and the stimulus thresholds were higher at the stimulation sites 2 cm anterior to the points 3 cm, 5 cm, and 11 cm lateral to the vertex. When positioning electrodes in the parietal direction to induce leg Tc-MEPs, leaving a greater distance between the electrodes may allow the stimulus to be transmitted deeper within the brain, thus improving the leg Tc-MEP induction rate.

In our hospital, electroencephalogram (EEG) Teaching conference was held weekly by face-to-face manner before March 2020 and completely replaced by the web after April 2020 due to COVID-19 pandemic. Here, we report the usefulness and points to be improved for EEG Teaching conference via a web meeting system based on the questionnaire survey to the participants. Methods: We analyzed the results of a questionnaire survey using the Internet system at the end of fiscal year of both 2020 and 2021. Results: The number of survey respondents/targeted individuals was 38/152 in 2020 and 75/179 in 2021, respectively. The percentage of all respondents participating in web conference after April 2020 was 37％ in 2020 and 55％ in 2021, respectively. Highly appreciated points for the web conference included the ability to join from anywhere, optimal display system of EEG waveforms, and comfortable situation for participation. Points to be improved included telecommunication trouble, secure protection of patients’ private information, less eager attention of participants. All respondents in both 2020 and 2021 expressed a preference for either web-only or a hybrid format combining web and face-to-face meetings. Conclusion: The evaluation for the web EEG conference was so high enough to continue, and several raised problematic points could be improved.

Motor unit number estimation (MUNE) and motor unit number index (MUNIX) are electrophysiological testing methods to assess functional motor unit number in neuromuscular diseases. In this study, we investigated the significance of assessing functional motor unit number using MUNIX and MUNE in patients with motor neuron disease (MND) and myopathy (MYO). MUNIX and MUNE were performed using the abductor pollicis brevis muscle as the test muscle, and the results were compared between 10 MND patients, 13 MYO patients, and 10 healthy subjects (CNT). MUNIX was lower for both MND and MYO compared to CNT, indicating that the motor unit size index (MUSIX), the exponential function alpha value used to calculate MUNIX, may be used to differentiate them. Furthermore, MUNE was also lower in MND and MYO than in CNT, and since MUNIX and MUNE are lower when the CMAP amplitude is low, it is important to confirm the motor unit size. Single motor unit potential (SMUP) amplitudes in MUSIX and MUNE, which are indices of motor unit size, were higher in MND, which may help differentiate MND from MYO.

The case was of a 26-year-old woman who worked in the poultry farming industry. Being concerned about the effect of her sedentary lifestyle on her health, she started going to a gym. One day, four months later, the gym was crowded, and her trainer was absent, so she performed only bench presses (10 kg, 20 sets, as usual) without doing warm-up exercises first, and then went home. The next morning, she experienced severe pain from her posterior neck to shoulder and lateral chest on the right. The pain gradually subsided, but the heaviness from the right shoulder to lateral chest persisted, especially when she raised her right arm. She visited our department seven months after the pain began. She had a right winged scapula and atrophy of the right serratus anterior muscle. Nerve conduction study of the long thoracic nerves revealed lower amplitude of compound muscle action potentials in the right serratus anterior muscle than in the left, and needle electromyography of the right serratus anterior muscle showed findings of early reinnervation. There were no notable abnormalities in other muscles. She was diagnosed with neuralgic amyotrophy presenting isolated right long thoracic nerve palsy and was treated conservatively. Even 27 months after the onset of pain, she still felt the heaviness from the right shoulder to lateral chest when she raised her right arm. Electrophysiological examinations were useful in confirming that neuralgic amyotrophy in our case presented isolated palsy of the right long thoracic nerve.

A 59-year-old man presented with progressive lower-limb weakness and abnormal lower limb sensation over 4 months. Nerve conduction studies showed ulnar nerve demyelination in the forearm of the and severe neuropathy in the lower extremities. Serum protein electrophoresis was unremarkable, but serum immunofixation electrophoresis revealed IgA-lambda gammopathy, leading to the diagnosis of POEMS syndrome. Characteristic neurophysiological findings should prompt immunofixation electrophoresis to diagnose POEMS syndrome.

In electroencephalography (EEG) interpretation, eye movement artifacts can sometimes be misinterpreted as frontal slow waves. The most reliable method to differentiate them is to check the electrooculogram (EOG) recorded simultaneously with the EEG. However, in routine EEG interpretation, it is common to differentiate them without using EOG, based on two points: 1) the amplitude decay of the waveform from the frontopolar to the frontal electrodes is steep, and 2) The slow wave components of eye movement potentials have unnatural waveforms compared with brain waves. In this case, we observed semirhythmic slow waves at both frontopolar electrodes (Fp1, Fp2), with poor distribution to adjacent frontal electrodes, which required differentiation from eye movement artifacts. The slow waves were confirmed to be brain waves by simultaneous EOG recording. This case illustrates the possibility of misinterpreting slow waves originating from the frontal lobe as eye movements when the dipole is tilted forward rather than perpendicular to the frontal electrodes, resulting in the negative potential predominance of frontopolar electrodes. It was reaffirmed that when there is a problem in differentiating between them, checking EOG recorded simultaneously with the EEG can enable accurate differentiation.

Magnetic field measurement has potential to evaluate biological current activity with high spatial resolution. Using a SQUID magnetometer designed to detect three-directional components of magnetic field and a spatial filter method, we attempted to evaluate the electrical activity of a hand muscle whose surrounding conductivity is not uniform. The estimated electrical currents of single motor unit in abductor pollicis brevis (APB) evoked by very weak electrical stimulation for the median nerve at the elbow was visualized. In the area the APB muscle was thought to be located, inward currents almost perpendicular to the direction of the muscle fibers and electrical currents in the distal and proximal direction parallel to the muscle fibers were simultaneously observed. These currents are considered to be activity near the neuromuscular junction and could be a quantitative indicator of the single motor unit activity. Therefore, magnetomyography could be another method replacing needle electromyography.