Moriichiro Takase

Abnormal muscle response (lateral spread) and F-wave in patients with hemifacial spasm

In patients with hemifacial spasm (HFS) the spasm is due to cross compression of the facial nerve by a blood vessel and microvascular decompression (MVD) has proved to be a successful treatment. Abnormal muscle response (AMR), which can be elicited by one facial nerve branch stimulation in muscles innervated by other branches of the facial nerve, is specific for patients with HFS, and the AMR consists of a constant response occurring about 10 ms after stimulus and an afterdischarge with long duration (variable response, autoexcitation). The F-wave in facial muscles is a small recurrent discharge that antidromically propagates to the facial motonucleus and returns orthodromically down the same axon. We measured the AMRs and F-waves of facial muscles in HFS patients in order to investigate the relationship of both potentials and the origin of the AMRs. We obtained facial nerve evoked electromyograms from 10 HFS patients. The afterdischarges of the AMRs and the enhanced F-waves were always elicited at the same time by marginal mandibular branch stimulation of the facial nerve. There was a linear correlation between the duration of these two potentials in each case. Between the duration of the afterdischarge of the AMRs elicited in the mentalis muscles by the zygomatic branch stimulation of the facial nerve and that of the F-waves in the mentalis muscles, there was also a linear correlation in 10 cases. These results suggest that the F-wave and the afterdischarge have the same origin and that the AMR is an exaggerated F-wave.

Transcranial magnetic stimulation-induced changes in EEG and responses recorded from the scalp of healthy humans

We determined the changes and responses in the electroencephalogram (EEG) induced by transcranial magnetic stimulation (TMS) of the scalp of five healthy men. The center of a circular coil was positioned at the vertex, and 80 stimulations were administered clockwise with the maximum output of electric current. To reduce stimulus artifacts, we created a circuit that blocked the input for 150 ms after stimulation. EEGs were recorded from F3,4, C3,4, P3,4, and T3,4. The following results were obtained: (1) slowing of the EEG was observed immediately (150 m) after each stimulation. The incidence of changes ranged from 25-80%; their duration ranged from 200-600 ms. (2). Electroencephalographic responses in the averaged form appeared as gentle positive waves. In some subjects and leads, 1 to 3 negative peaks were fused. The methods used in the present study may be useful in evaluating the sensitivity to TMS of patients with stroke and other types of brain injury.

Relationship between clinical symptoms and EEG findings in borderline personality disorder.

Abstract: Borderline personality disorder (BPD) was diagnosed in female patients (N=41) between the ages of 18 and 30 using the Diagnostic Interview for Borderline Patients (DIB) and DSM‐III. Comparing the EEG findings of BPD (N=18) and non‐BPD (N=21) groups, there were no EEG findings characteristic of BPD. We also assessed the relationship between the EEG findings and DIB items. Positive spikes appeared in patients with high scores for Impulse Action Patterns, while wave and spike phantoms were observed in patients with high scores for Interpersonal Relations. Dividing the patients into BPD and non‐BPD groups, a similar tendency to that observed from an analysis of all patients was observed in the non‐BPD group, but no such tendency was observed in the BPD group. The results suggest that BPD patients include those in whom vulnerability of cerebral function plays an important role in the development of these two clinical symptoms as well as those in whom vulnerability of cerebral function plays almost no pathogenic role.

New methods for removing saccades in analysis of smooth pursuit eye movement

New computation methods for removing saccades in analysis of smooth pursuit eye movement characteristics were developed. They have removed saccades more completely than previous methods, and were very effective especially for noisy data recorded by the EOG method. The fully developed method was applicable to eye movement data in tracking of pseudo-random target movement as well as deterministic target movement. Furthermore, the methods were also useful for extracting the number and magnitudes of saccades more precisely.

Effect of repetitive stimulation on lateral spreads and F-waves in hemifacial spasm

The lateral spread (LS) response, which can be elicited in muscles innervated by other branches of the facial nerve, is electromyographycally specific for patients with hemifacial spasm (HFS), occurring about 10 ms after stimulus. The F-wave in facial muscles, which is a late response that antidromicaly propagates to the facial motonucleus and returns orthodromicaly down the same axon, revealed a trend toward enhancement in patients with HFS. The LSs were facilitated by repetitive stimulation during the microvascular decompression (MVD) operation, which has proved to be a successful treatment, and the F-waves were also facilitated by repetitive stimulation on the spasm side more than on the normal side. Greater facilitation of these responses was in direct proportion to higher stimulation rates and greater numbers of stimulations. The repetitive stimulation of the facial nerve may result in activation of the motoneuron pool and in the lowering of the threshold of somatic membranes. These results support the hypothesis that hemifacial spasm is caused by hyperexcitability of the facial motonucleus, which is increased by antidromic repetitive stimulation.

F-wave in patients with hemifacial spasm: observations during microvascular decompression operations.

In patients with hemifacial spasm (HFS), the spasm is due to cross compression of the facial nerve by a blood vessel. There are currently two hypotheses how the cross compression can cause HFS: 1. the spasm is caused by ephaptic transmission and hyperexcitability at the site of compression; and 2. the spasm is caused by hyperexcitability in the facial motonucleus. In peripheral nerves, F-waves, which result from the backfiring of antidromically activated anterior horn cells, have been proposed as indices of anterior horn cell excitability. Enhancement of the F-waves in facial muscles also indicates increased excitability of the facial motonucleus. On the other hand, abnormal muscle response (AMR), which can be elicited by stimulating one branch of the facial nerve and recording electromyographically from muscles innervated by other branches of the facial nerve, is specific for patients with HFS. We have therefore measured the AMRs and the F-waves in the facial muscle of HFS patients under anesthesia in order to investigate the excitability of the facial motonucleus. We obtained facial nerve evoked electromyograms from 14 HFS patients during microvascular decompression (MVD) operation. The F-waves, obtained with surface electrodes from the mentalis muscle, were defined as the second response after the M-wave. The F-waves in facial muscles cannot usually be elicited during surgical anesthesia using inhalation anesthetics. However, the F-waves were elicited on the spasm side in 10 out of 14 patients with HFS and the F-waves disappeared after MVD under anesthesia, as the early responses (R1) of the blink reflex were elicited on the spasm side before MVD under anesthesia. The F-waves elicited during anesthesia were suppressed significantly, compared with those before MVD. These results suggest that excitability in facial motonucleus increased on the spasm side.

Long-latency response to transcranial magnetic stimulation in patients with hemifacial spasm.

OBJECTIVE We studied the long-latency response of the orbicularis oris muscle elicited with transcranial magnetic stimulation in patients with hemifacial spasm (HFS) and evaluated the excitability of the facial nucleus. METHODS We compared the thresholds on both sides in 8 normal volunteers and 7 patients with hemifacial spasm. The thresholds were determined as the lowest intensity required to produce motor evoked potentials with an amplitude of at least 50 microV in the orbicularis oris muscle. Average values were given as means +/- standard deviation. Wilcoxons rank sum test was used for comparisons between the sides of normal subjects and of patients with HFS with respect to the threshold stimulus. RESULTS There was no significant difference between the thresholds on the two sides of the normal subjects (mean 1.88+/-5.30%, P > 0.05). In patients with HFS, there was a significant difference between the thresholds on the spasm side and the normal side (mean 20.7+/-13.0%, P < 0.05) In one patient studied after MVD, the difference between both sides disappeared. CONCLUSION The difference between the thresholds in patients with HFS and the normalization in threshold after MVD suggested that the mechanism of HFS was hyperexcitability of the facial nucleus.

Strength-duration curve of conductive spinal cord evoked potentials in cats

Strength-duration curves of the ascending and descending conductive spinal cord potentials (SCEPs) in cats were obtained using constant current stimuli. For the formulation of numeric indices of excitability, the rheobase is defined as the minimal current strength below which response cannot occur even if the current continues, and the chronaxie is defined as the minimal duration of a current required to evoke the potential at twice the rheobase strength. The chronaxies and rheobases were calculated from the constructed strength-duration curves. The purpose of this study is to produce strength-duration curves and to evaluate the utility of chronaxies and rheobases for SCEPs. This study showed the following results: (1) there was a hyperbolic relationship between stimulus strength and stimulus duration at threshold values, similar to that seen in peripheral nerves; (2) the ascending and descending tracts of SCEP were mediated through the same pathway (based on the similar chronaxies and rheobases); (3) following spinal cord compression the chronaxie and rheobase increased significantly (P < 0.05), which is similar to peripheral nerve disturbance. However, the rheobase decreased significantly following slight spinal cord compression (P < 0.05) and systemic cooling (P < 0.01), and the strength-duration curve shifted showing a tendency towards decrease of the galvanic threshold, therefore, amplitude augmentation with slight compression and with decrease in temperature seems to contribute to the reduction of the threshold. The strength-duration curve, the chronaxie and the rheobase may be useful in assessing spinal cord function.

Dynamics of saccadic eye movement depending on diurnal variation in human alertness

From the viewpoint of traffic accident prevention or intelligent interface construction, the proposal of indices which can simply evaluate alertness is desirable. In this paper, to investigate the possibility of alertness evaluation using saccadic eye movement (SC), we report 24-hour sleep deprivation experiments and investigate the relationship between the diurnal variation and SC dynamics. It has become clear that three parameters of SC, namely, the peak velocity/duration ratio, the normalized peak velocity, and the normalized duration, have strong correlations with the amplitude component of brain waves, sleepiness, and subjective alertness. These results imply that SC dynamics have a high dependence on the two alertness indices, physiological and subjective, and the possibility of application of the SC dynamics to alertness evaluation is shown.

Relationship between vigilance levels and characteristics of saccadic eye movement

The purpose of this study was to investigate the possibility for evaluating vigilance levels using a parameter of saccadic eye movement. EEG was measured and analyzed by means of fast Fourier transform, and the spectral power of /spl alpha/ and /spl beta/ wave bands were obtained so as to extract [/spl beta/]/[/spl alpha/+/spl beta/] which was assumed to reflect vigilance levels. Eye movement was measured so as to calculate saccadic peak velocity (SPV) and relative SPV (RSPV) which was normalized by the mean SPV at the corresponding amplitude of saccade. The relationship between [/spl beta/]/[/spl alpha/+/spl beta/] and RSPV was investigated and it revealed that RSPV decreased according to the decline in the vigilance level. This indicates the possibility for evaluating vigilance levels using RSPV.