Although various executive functions are thought to be subserved by different regions in the prefrontal cortex, the changes in the cerebral blood flow during the performance of problem-solving tasks involving reasoning (Crack-the-Code tasks) have not yet been investigated. In the present study, 28 healthy adults were asked to perform a total of eight tasks in four blocks, and NIRS measurements were taken from the frontal region. The results showed that as the difficulty level increased, the percentage of correct answers decreased, and the number of movements, reaction time, total time, and evaluation time increased. In terms of cerebral hemodynamics, the level of oxy-Hb in the left DLPFC in the block with higher difficulty, and in the left and right mPFC in the latter half of the two tasks within this block, increased significantly. These results suggest that, with increasing task difficulty, a trial-and-error approach is reflected in the problem solving performance; that the left DLPFC is involved throughout the problem solving process; and that, in complex problem solving, the right mPFC region is involved in the processing of the both prefrontal cortex.

Repetitive nerve stimulation study is one of the useful electrodiagnostic test in the evaluation of the patients with suspected neuromuscular junction disorders. The diagnostic yield increases with stimulation of proximal nerves. Although repetitive nerve stimulation for spinal accessory nerve is preferred, proximal stimulation has some technical problems. Isometric electrode position is essential for the test. Minimizing shoulder movement is difficult in upper trapezius muscle recordings. We use the middle trapezius muscle in repetitive nerve stimulation test for minimizing the effect of shoulder movements. The fluctuation of compound muscle action potential is evaluated by using the mean value of continuous difference (MCD). MCD is often used for calculating jitter in single fiber electromyography. Our method using the middle trapezius muscle recording without fixation of shoulder at sitting positon has lowest MCD values in the repetitive nerve stimulation test for spinal accessory nerve. This means middle trapezius muscle recording without fixation of shoulder for spinal accessory nerve stimulation is suitable for isometric electrode position, and is one of the useful methods.

We describe nerve ultrasound in the symptom-induced limb position for a patient with true neurogenic thoracic outlet syndrome (TNTOS). A 14-year-old girl presented atrophy of the right thenar eminence and increased numbness of the right forearm by the right upper arm elevation. She was diagnosed with TNTOS based on the abnormal results of a nerve conduction study. Nerve ultrasound of brachial plexus in the intercostal space revealed the fibrous band (FB) extending from the elongated transverse process of the right C7 vertebra. Additional observation while elevating the right upper limb to exacerbate symptoms revealed that the lower trunk was gradually pushed up by the medial edge of the middle scalene muscle and squeezed in contact with the FB. After surgical removal of the FB with the tip of the elongated transverse process of the right C7 vertebra, good functional recovery was obtained. We considered that nerve ultrasound in the symptom-induced limb position would be useful for detailed identification of the site and anatomical cause of nerve disturbance in TNTOS cases.

[Purpose] The magnetic field evoked from the cervical spinal nerve after median nerve stimulation at the elbow was measured by magnetoneurography (MNG), and the conduction of nerve activity in the upper cervical spinal cord could not be confirmed. In this study, we measured the evoked magnetic field of the upper cervical spinal cord after the axillary median nerve stimulation, and visualized the reconstructed current in healthy subjects. [Material & Method] The subjects were five healthy adults without limb neurological symptoms, five nerves, aged 26–60 years (average 41 years), four males and one female. The median nerve was stimulated between the biceps and triceps muscles 15–17 cm proximal from the medial epicondyle of the humerus, and the evoked magnetic field of the upper cervical nerve was measured by using MNG. We monitored the compound muscle action potential (CMAP) of the abductor digiti minimi muscle to avoid current spread to the ulnar nerve. The stimulus intensity was set at the supramaximal level of CMAP of the abductor pollicis brevis muscle (6.6–9.4 mA, average 7.68 mA), with a stimulus frequency of 5 Hz and a stimulus duration of 0.3 ms. The evoked magnetic fields were recorded by the MNG system using a 40-kHz sampling rate and 100–5000-Hz bandpass filter, and 4000 responses were averaged. [Result] In all five cases, the magnetic field data derived from nerve activity in the upper cervical spinal cord was observed. The intensity of magnetic fields evoked by median nerve stimulation at axillar were about 1.5–2 times stronger than at the elbow. In particular, the upward propagation of inward reconstructed current, which is thought to correspond to the depolarization point on the nerve membrane, was observed up to the C2 level in three of the five cases and up to the brainstem area in the remaining two cases. The average conduction velocity estimated from the reconstructed current was 72.8 m/sec (65–78 m/sec), and visualization of nerve activity was confirmed by superimposing simple cervical spine X-ray images. [Conclusion] Visualization of the evoked magnetic fields in the cervical spinal cord has already been reported by Sumiya et al. However, those in the upper cervical spinal cord could not be obtained by the conventional method due to the influence of temporal dispersion, but the axillary stimulation made recording and visualization of nerve activity in the upper cervical spinal cord possibility. In the future, MNG is expected to be a useful test for functional image evaluation of upper cervical spinal cord diseases.