Abstract: Background and Purpose: We report decremental responses to repetitive nerve stimulation (RNS) in 11 patients diagnosed with X-linked spinobulbar muscular atrophy (X-SBMA). Methods: The compound muscle action potential (CMAP) of the right abductor digiti minimi (ADM) and trapezius (TZ) in response to a 3-Hz stimulation of the ulnar nerve at the wrist and accessory nerve at the neck were recorded by surface electrodes. Results: A decremental response to RNS was observed in 90.9% of the TZ muscle and 27.2% in the ADM muscle of patients with X-SBMA. Conclusion: These electrophysiological features of X-SBMA are considered to be useful for diagnosis of X-SBMA. Furthermore, the waning phenomena that mostly appeared in the TZ muscle and increment of CMAP in RNS after the exercise also suggest a unique manifestation in X-SBMA.
Abstract: A simple and reliable method for recording sensory nerve action potentials (SNAPs) of the medial plantar nerve is described. Medial plantar SNAPs were recorded by placing surface electrodes on the sole. Ring electrodes were used for orthodromic stimulation at the big toe. Sixty-four healthy subjects ranging in age from 13 to 81 years were examined to establish normal values. Mean amplitude for the medial plantar SNAP was 4.7 +/- 2.8 microV and mean maximum conduction velocity was 43.5 +/- 6.4 m/s. The normal values for amplitude obtained for the medial plantar SNAPs were higher than those obtained by the method of Guiloff and Sherratt, and the sensitivity of our method for diagnosis of early sensory neuropathy was relatively higher. The method should therefore be useful in the diagnosis of early sensory neuropathy.
Abstract: We studied the effect of injecting botulinum toxin A (BTX-A) into the pars ciliaris--also known as Riolan's muscle--of patients with eyelid apraxia (ELA). Six patients with ELA were treated with injections of BTX-A into the region of Riolan's muscle at the medial and lateral portions of the upper and lower pretarsal orbicularis oculi. Clinical benefit was seen in all 6 patients, 2 of whom had previously been treated with conventional pretarsal injections of BTX-A and had not improved. BTX-A injections into Riolan's muscle are effective as treatment for ELA. The proposed mechanism is not that of muscle relaxation but rather modulation of the somatosensory cortex, similar to that of a 'sensory trick' in patients with dystonia.
Abstract: We used electric median nerve stimuli to elucidate the functional properties of neurons in the human secondary somatosensory cortex during exploration of small objects and muscle contraction. Somatosensory evoked fields were recorded from nine healthy subjects with a 204-channel neuromagnetometer. Electrical stimuli were applied once every 3 s to the left median nerve at the wrist. The conditions during the stimulation were rest (control session), exploration of small objects (exploration session) and clenching the hand while the wrist was being electrically stimulated (clench session). The strengths of equivalent current dipoles of evoked fields from the secondary somatosensory cortex were increased during the exploration session, but those of evoked fields were decreased by the clench session.
Abstract: We recently recorded somatosensory evoked fields (SEFs) elicited by compressing the glabrous skin of the finger and decompressing it by using a photosensor trigger. In that study, the equivalent current dipoles (ECDs) for these evoked fields appeared to be physiologically similar to the ECDs of P30m in median nerve stimulation. We sought to determine the relations of evoked fields elicited by mechanically stimulating the glabrous skin of the great toe and those of electrically produced P40m. We studied SEFs elicited by mechanical and electrical stimulations from the median and tibial nerves. The orientations of dipoles from the mechanical stimulations were from anterior-to-posterior, similar to the orientations of dipoles for P30m. The direction of the dipole around the peak of N20m from median nerve electrical stimulation was opposite to these directions. The orientations of dipoles around the peak of P40m by tibial nerve stimulation were transverse, whereas those by the compression and decompression stimulation of the toe were directed from anterior-to-posterior. The concordance of the orientations in ECDs for evoked fields elicited by mechanical and electrical stimulations suggests that the ECDs of P40m are physiologically similar to those of P30m but not to those of N20m. The discrepancy in orientations in ECDs for evoked field elicited by these stimulations in the lower extremity suggests that electrical and compression stimulations elicit evoked fields responding to fast surface rubbing stimuli and/or stimuli to the muscle and joint.
Abstract: We studied the variation in the human median nerve activity during ischemia by measuring compound nerve action magnetic fields (CAFs). Temporal increases in the CAF during ischemia were successfully visualized on isofield contour maps. Intense paresthesias were induced after 29 +/- 5 s (mean +/- SD) of ischemia, which consistently reached a maximum after 4 min 55 +/- 12 s. The variations in CAFs were consistent with changes in sensory perception. The hyperexcitability in large myelinated axons can be visualized as temporary increases in CAF. These results are the first to demonstrate the efficacy of magnetic-recording techniques, which allow monitoring of changes in neural activity.
Abstract: We studied the cortical evoked fields elicited by the examiner's touch on glabrous skin of the subject's index finger. Two main components of evoked fields were elicited, and these dipoles were located in the primary somatosensory cortex contralateral to the side of the subject's index finger touched by the examiner. When the timing of removal of the examiner's finger triggered the data acquisition using the photosensor, the strength of the dipole from early evoked fields was stronger than that from late ones. We showed that these evoked fields were elicited by removal and touch of the examiner's finger respectively in response to the mechanical compression and decompression of the skin.
Abstract: We have summarized the history of electroencephalography(EEG) since 1875, when a paper by Richard Caton was published describing the first EEG recordings in animals. Somatosensory evoked potentials (SEPs) were recorded by George Dawson in 1951. Thereafter, SEPs were developed for clinical use with other evoked potentials such as auditory evoked potentials(VEPs). To understand evoked potentials, related mechanism of induction of far-fields-potentials(FFP) following stimulation of the median nerve has been discussed. SEPs consisted of P9, N9, N10, P11, N11, N13, P13, P14, N18, N20 and P20/P22. Scalp recorded P9 FFP arises from the distal portion of the branchial plexus as reflected by N9 stationary negative potential recorded over the stimulated arm. Cervical N11 and N13 arise from the root entry zone and dorsal horn, respectively. Scalp recorded P13, P14 and N18 FFP originate from the brainstem. In this communication, magnetoencephalography(MEG) and results of one of our recent studies on somatosensory evoked fields(SEFs) are also discussed. One of the important features of MEG is that magnetic signals detected outside the head arise mainly from cortical currents tangential to the skull. Since the net postsynaptic current follows the orientation of cortical pyramidal cells, the MEG signals mainly reflect activity of the fissural cortex, whereas radial current may remain undetected. In our study, we demonstrated SEFs elicited by compression and decompression of a subject's glabrous skin by a human operator. Their dipoles were tangentially oriented from the frontal lobe to parietal lobe.
Abstract: OBJECTIVE: To determine whether patients with cervical dystonia have electrophysiological signs of disinhibition in the somatosensory cortex by recording high-frequency oscillations (HFOs) in somatosensory evoked potentials (SEPs). METHODS: HFOs were recorded in 13 patients and 10 age-matched control subjects, and the data were analyzed statistically by paired comparison and by Pearson's correlation. RESULTS: In patients with cervical dystonia, the early part of HFOs showed a significant decrease in amplitude, and the amplitude ratios of both early and late parts of HFOs/N20 potential were also significantly decreased. The amplitudes of HFOs and N20 potential were linearly correlated in the control subjects but not in dystonia patients. CONCLUSIONS: Patients with cervical dystonia may suffer from a disturbance of inhibition in the sensory cortex. This disturbance is reflected by decreased HFO amplitude, representing decreased activities of inhibitory interneurons in area 3b.
Abstract: The authors describe a 16-year-old boy with severe muscular atrophy and signs of peripheral neuropathy compatible with Charcot-Marie-Tooth disease. Abnormalities in the cerebellum and central somatosensory pathway were also noted. Gene analysis revealed a novel gross insertion mutation in exon 2 of the connexin32 gene along with a 21-base pair duplication resulting in a seven-amino acid insertion in the first extracellular loop of the protein.
Abstract: OBJECTIVES: To elucidate the functional properties of neurons in the human primary (SI) and ipsilateral and contralateral secondary (iSII or cSII) cortices in response to stimuli during finger movement.METHODS: We measured somatosensory evoked fields (SEFs) produced by electric stimuli delivered to the median nerve at 0.2 Hz in 6 healthy subjects.RESULTS: The amplitudes of evoked fields from both iSII and cSII were gradually attenuated with time. Consecutive blocks of trials were obtained to assess the habituation of each evoked field. Complex finger movements with attention (gating session) increased the amplitude of evoked fields from the iSII cortices but reduced the amplitudes of evoked fields from the cSII cortices (P<0.01). In contrast, the amplitude of P30 m from the SI did not show habituation effects but decreased significantly in the gating session (P<0.01).CONCLUSIONS: The enhanced iSII as well as suppressed cSII cortices during complex finger movements with attention are not only considered to be result of gating effect but also attention.
Abstract: Somatosensory evoked fields were recorded to determine the effects of movement and attention on high-frequency oscillations during active finger movements of the ipsilateral and contralateral sides in response to electrical stimulation of the median nerve. A whole-scalp neuromagnetometer was used to record somatosensory evoked fields from eight subjects following electric median nerve stimulation at the wrist. The following three sessions were performed: (1). rest, (2). movement of fingers on the ipsilateral in response to stimulation and (3). movement of fingers on the contralateral in response to stimulation. The somatosensory evoked fields with a wide-bandpass (0.1-1000 Hz) were recorded. High-frequency oscillations and N20m were separated by subsequent high-pass (> 300 Hz) and low-pass (< 300 Hz) filtering. The maximum amplitude of high-frequency oscillations decreased during finger movements accompanying a decrease in somatosensory N20m dipole strength. Activation of the motor cortex appeared to suppress both the amplitude of high-frequency oscillations and the N20m dipole strength.
Abstract: When stimulating the mixed nerve to record evoked potential, both sensory and motor fibers are activated before entering the spinal cord. The N10 potential has been described as an antidromic motor evoked potential based on results obtained by recording at the anterior midneck. In the present study, we examined the changes in latencies of Erb's potential, N10, and N13 by stimulating the median nerve distally at the wrist and proximally at the elbow. The conduction velocity of N10 calculated by the difference between N10 latencies at the two stimulation points was consistent with motor conduction velocity, although N13 conduction velocity estimated by the same method reflected a sensory conduction velocity. A positive relation was also observed between the indirect latency from the stimulation point to the anterior root as calculated using the equation (F - M - 1) / 2 (ms) and the direct latency to the negative peak of the N10 potential. Our data support the notion that N10 represents antidromic motor potential originating in the spinal entry zone of the anterior root.
Abstract: We studied the effect of stimulus intensity on latencies of short-latency somatosensory evoked potentials (SSEP) by measuring both onset and peak latencies individually. The latencies of N9, N13, N20 and N9-N13 peripheral conduction time (PCT) of median nerve (MN) SSEP, and N8, N23, P37 and N8-N23 PCT of tibial nerve (TN) and sural nerve (SN) SSEP significantly shortened with increasing stimulus intensity by onset latency measurement. However, those latencies by peak latency measurement were less significantly shortened or had only a trend of latency shortening without statistical significance. In contrast to PCT, N13-N20 central conduction time (CCT) of MN-SSEP and N23-P37 CCT of TN- or SN-SSEP showed no latency changes with the increased stimulus intensity by both onset and peak latencies measurement. As peak latencies had greater interindividual variability than onset latencies shown by larger standard deviation, shortening of onset latencies were more consistent than that of peak latencies. We think shortening of onset latencies indicates the recruitment of faster conduction fiber along with increased stimulus intensity. As the degree of latency shortening was less if stimulus intensity was above 2.5 times sensory threshold, the stimulus intensity greater than 2.5 times the sensory threshold should be used for clinical application.
Abstract: We report a 10-year-old boy with cholinergic urticaria associated with epileptic seizure and abnormalities on electroencephalogram. In March 1999, many red wheals developed over the entire body during exercise and at increased body temperature. In April, systemic red wheals developed during exercise. Simultaneously, loss of consciousness was noted for 2 to 3 minutes. After the patient's body was cooled, consciousness improved, and these exanthemas disappeared. In the Department of Dermatology, his illness was diagnosed as cholinergic urticaria. Neurologically, a heat tolerance and mental strain induced cholinergic urticaria, followed by generalized epilepsy(clonic seizure). In addition, electroencephalography revealed high voltage polyspikes and 14 Hz positive spikes. The mechanism involved in cholinergic urticaria associated with epileptic seizure was assumed as follows: sweat-promoting stimuli, such as heat, exercise and tension, stimulate the autonomic center in the diencephalon or brain stem, and excitation in the autonomic center is transmitted to the efferent sympathetic nerve, causing cholinergic urticaria; when the intensity of stimulation is high, the autonomic center exhibits abnormal activities and causes epileptic seizure.
Abstract: High-frequency oscillations (HFOs) and the underlying P37 primary somatosensory response evoked by posterior tibial nerve stimulation were recorded in patients with Parkinson's disease (PD) and in those with multiple system atrophy (MSA), as well as in normal controls. In order to increase the signal-to-noise ratio, we averaged a large number of responses (9998 epochs) with a high sampling rate (20 kHz per channel). HFOs were extracted by filtering the wide band-pass recording of the P37 potential with a 600-900 Hz band-pass filter. High-amplitude HFOs were observed in both the PD and MSA patients. Furthermore, the duration of illness was positively correlated with the amplitude of HFOs. The results suggest that HFOs are enhanced by dysfunction of the basal ganglia.
Abstract: We describe a 16-year-old female patient affected by photo-induced temporal lobe epilepsy. During intermittent photic stimulation she showed a photoparoxysmal response in the EEG. This case was diagnosed from clinical symptoms, single photon emission computer tomography, and EEG data. The clinical symptoms were relieved by the administration of carbamazepine. As these photoparoxysmal responses were observed not only during photic stimulation, but also when patient was closing her eyes during an eye-opening test in complete darkness, we propose the existence of an alternative pathway such as from the extraocular muscles or orbicularis oculi, or activation of cortical activity due to the change of consciousness by closing eyes in inducing photosensitive epilepsy. We describe an additional case and discuss a novel aspect of photo-induced temporal lobe epilepsy.
Abstract: The scalp far-field potentials after median nerve stimulation at the wrist consist of P9, P11, P13, and P14 positive components. Earlier, Emerson et al. (1984) identified the "N10" negative potential in-between the P9 and P11 and claimed that this was not merely a passive return to the baseline after the P9 positive deflection but a distinct component reflecting a proximal brachial plexus volley. They thought N10 was a far-field potential having widespread distribution with a fixed latency. In this study we found that N10 was of higher amplitude after median nerve stimulation at the elbow than after stimulation at the wrist. Indeed the N10 latency was fixed from the lower anterior neck to the scalp, and its amplitude was maximum at the anterior lower neck. The latency of N10 was about 0.3 milliseconds longer than the Erb's potential and 0.15 milliseconds longer than the potential recorded from the lateral neck on the side of stimulation. The N10 amplitude increased in parallel with increased stimulus intensity. In order to explore the origin of the N10 stationary field potential, we designed a paired stimuli paradigm applied to the wrist (S1) and to the elbow (S2). The interstimulus interval between S and S2 was adjusted so that the timing of S2 was immediately after the traveling impulse produced by the S1 stimulus as it passed through the S2 stimulus site. This technique allowed stimulation of the anterior interosseous nerve selectively at the elbow while the median nerve originating from the wrist was undergoing refractory period. The response of (S1 + S2) - S1 showed only the N10 with absence of cervical and cortical responses, implying that N10 was activated, predominantly by the interosseous nerve, i.e., an antidromic motor volley, when the median nerve was stimulated at the elbow.
Abstract: A complementary DNA clone was isolated from human brain that encodes a glutamate transporter. Injection of RNA transcribed from this cDNA into Xenopus oocytes resulted in expression of a transport activity with a high affinity for glutamate (Km = 78.4 microM) and a dependency on external Na+. The cDNA sequence predicts a protein of 542 amino acids that is highly homologous to the congeneric proteins from rat and mouse brains. RNA blotting analyses revealed the expression both in the brain and in peripheral tissues.
