澁谷 和幹

Objective: Previous studies have shown that age, gender, and body mass index (BMI) affect amplitude of sensory nerve action potentials (SNAP), but the total effects of multiple factors or the most prominently affected nerves have not been elucidated. This study systematically investigated effects of these factors. Methods: Amplitude of SNAP of the median, ulnar, superficial radial, superficial peroneal, and sural nerves was measured in 105 healthy subjects. The effects of age, gender, and BMI on each nerve were estimated by multivariate linear regression analysis. Results: SNAP amplitude decreased with age in all five nerves. Women had greater SNAP amplitude than men in the upper limb nerves (median, ulnar, and radial), but not in the lower limb nerves (peroneal and sural). Similarly, greater BMI was associated with smaller amplitudes in the upper limb nerves, but not in the lower limb nerves. Multivariate analyses showed the three factors explained 50% of the variation in the median nerve, 46% in the ulnar nerve, and 22-32% in the remaining nerves. Conclusions: The effects of age, gender, and BMI on SNAP amplitudes are not identical in different sensory nerves. Age was strongly correlated with SNAP amplitude in the nerves tested, whereas gender and BMI affect amplitudes only in the upper limb nerves. Significance: Age, gender, and BMI should be taken into account in clinical practice, but the extent of influence depends on the sensory nerves examined. (C) 2009 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.

To assess the significance of distal compound muscle action potential (CMAP) duration for diagnosis of demyelinating neuropathies, electrophysiologic data were reviewed from 471 subjects, including 145 normal controls, 60 patients with chronic inflammatory demyelinating polyneuropathy (CIDP), 205 with other neuropathy, and 61 with amyotrophic lateral sclerosis (ALS). The duration of distally evoked CMAP was measured in the median, ulnar, tibial, and peroneal nerves. Optimal cut-off values were calculated with receiver-operating characteristic (ROC) curves. In comparison of normal controls and CIDP patients, ROC analyses showed the sufficient area under the curves (82-93%). When the cut-off values in the detection of demyelination were determined as the point with 98% specificity vs. normal on the ROC curves (median, 6.6 ms; ulnar, 6.7 ms; peroneal, 7.6 ms; tibial, 8.8 ms), the sensitivity was 77% for CIDP, with a specificity of 90% vs. ALS and 95% vs. diabetic neuropathy. The distal CMAP duration is a useful index for the detection of distal demyelination. We suggest the above cut-off values for each nerve as one of the electrodiagnostic criteria for demyelinating neuropathies, preferentially affecting the distal nerve terminals, such as CIDP.

Objective: The threshold tracking technique is a new approach to non-invasively assess biophysical properties of axonal membrane in human subjects. The aim of this study was to evaluate the effects of age and gender on excitability properties of human motor axons. Methods: Computerized threshold tracking was used to measure multiple excitability indices in median motor axons of 93 normal subjects (50 men; age, 20-86 years). Results: Regression analyses showed that the higher age was associated with longer strength-duration time constant (p = 0.03), smaller threshold changes in depolarizing threshold electrotonus (p = 0.02), smaller super-normality (p = 0.01), and steeper slope of the current-threshold relationship for hyperpolarizing currents (p < 0.001). There were slight sex differences in rheobase, threshold electrotonus, supernormality, late subnormality, and current-threshold slope, though they were significant only in the subgroup with age <50 years. Conclusions: Aging may increase persistent sodium cut-rents, inward rectification, and possibly, outward potassium currents. The combination of changes raises the possibility of slight membrane depolarization in elderly people. For the sex-related differences, further studies will be required with the evaluation of sex hormonal effects. Significance: Age-related effects on excitability properties are subtle, but should be taken into consideration in the clinical application of nerve excitability testing, particularly in elderly subjects. (c) 2008 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.

The potential therapeutic role of repetitive transcranial magnetic stimulation (rTMS) in epilepsy has been increasingly recognized. We investigated the effects of low-frequency rTMS in a patient with epilepsia partialis continua (EPC) due to cortical dysplasia. A 31-year-old female patient experienced EPC in the right upper and lower extremities, which had lasted for 15 years without generalized seizures. MRI showed focal megaencephaly around the motor cortex suggestive of cortical dysplasia. A figure of eight magnetic coil was placed over the hand motor area, and 100 stimuli with an intensity at 90% of motor threshold were given at 0.5 Hz. Immediately after rTMS, EPC was nearly abolished. The effects had continued approximately for 2 months, and the second trial resulted in the similar effects and time-course. Low-frequency rTMS was safe and well tolerated in this patient. These findings support the concept that rTMS decreases cortical excitability, and may be an effective treatment for focal partial seizures. (c) 2005 Elsevier B.V. All rights reserved.

Cortical dysplasia has been increasingly recognized as a cause of epilepsy. We describe herein a 31-year-old female patient with epilepsia partialis continua (EPC) in the right extremities, which had lasted for 15 years without generalized seizures and other neurological deteriorations. MRI showed a focal thickening around the left motor area, indicative of cortical dysplasia, with adjacent subcortical abnormal T2 high intensity, suggestive of dysmyelination. Transcranial magnetic stimulation revealed low motor thresholds and markedly prolonged latencies of motor-evoked potentials (MEP) of the affected side, consistent with hyperexcitability of the cortical motoneurons accompanied by dysmyelination. This case demonstrates that motor cortex dysplasia can result in a mild and non-progressive form of epilepsia partialis continua, associated with the characteristic MRI and MEP abnormalities. (C) 2004 Elsevier B.V. All rights reserved.