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ABSTRACT: To establish the electrophysiological mappings of nonhuman primates by using magnetocardiogram (MCG) data and obtain the normal values of MCG parameters, we used 64-channel superconducting quantum interference devices to measure 8x8 MCG data for 95 cynomolgus monkeys (Macaca fascicularis, 51 female and 44 male). The PQ interval, QRS duration, QT interval and QTc were respectively 79+/-14 ms, 42+/-7 ms, 222+/-23 ms and 363+/-25 (mean+/-SD), and these parameters did not differ significantly between female and male monkeys. These results indicate the normal values of the MCG parameters of the cynomolgus monkey and should facilitate animal experiments in magnetocardiography.
Physics in Medicine and Biology 04/2008; 53(6):1609-18. · 2.83 Impact Factor
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Kei On,
Shigeyuki Watanabe,
Satsuki Yamada,
Noriyuki Takeyasu,
Yoshitsugu Nakagawa,
Hidetaka Nishina,
Takafumi Morimoto,
Hideaki Aihara,
Taizo Kimura,
Yoko Sato, Keiji Tsukada,
Akihiko Kandori,
Tsuyoshi Miyashita,
Kuniomi Ogata,
Daisuke Suzuki,
Iwao Yamaguchi,
Kazutaka Aonuma
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ABSTRACT: Magnetocardiography (MCG) is sensitive to minute cardiac electric abnormalities, but its clinical utility in diagnosing ischemic heart disease (IHD) has not been established. The present study examined the usefulness of an integral MCG value of ventricular repolarization in patients with IHD.
MCG was performed at rest in 14 patients with coronary stenosis >75% confirmed by coronary angiography (IHD group) using a 64-channel system, and then the sum of the 64-channel integral values of the QRS or JT intervals (QRSi and JTi, respectively) was calculated. The JTi/QRSi value indicated the total power of currents in JT compared with those in QRS. These measurements were repeated within 2 weeks after coronary revascularization. The Control group comprised 30 healthy volunteers. The baseline value of JTi/QRSi was significantly smaller in the IHD than in the Control group, but after revascularization it increased and did not significantly differ from the Control group. No significant difference in ST deviation was identified by electrocardiography (ECG) before and after coronary revascularization. Analysis of the Control group revealed that JTi/QRSi was not affected by age.
The JTi/QRSi of the MCG is more sensitive to coronary stenosis than ECG, and this parameter improves soon after coronary revascularization.
Circulation Journal 10/2007; 71(10):1586-92. · 3.77 Impact Factor
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ABSTRACT: As a new clinical examination apparatus for cardiac diseases, attention is focused on the magnetocardiograph, which can represent electrophysiological phenomena of the heart noninvasively as graphical information. We have been developing a compact and portable high-temperature superconducting magnetocardiograph based on our technology for magnetocardiographs using low-temperature superconductors. Since a high-temperature superconducting magnetocardiograph can work with liquid nitrogen cooling, it allows miniaturization and lower running costs. Hence, it is expected to help popularize magnetocardiographs by its use in smaller hospitals and in group medical examinations in the field. In this paper, we introduce the prototype high-temperature superconducting magnetocardiographs we have made, and report the fabrication technology for a highly sensitive high-temperature SQUID and the technology for external noise shielding and compensation. © 2007 Wiley Periodicals, Inc. Electron Comm Jpn Pt 2, 90(4): 46– 55, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjb.20273
Electronics and Communications in Japan (Part II Electronics) 03/2007; 90(4):46 - 55. · 0.18 Impact Factor
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Akihiko Kandori,
Tsuyoshi Miyashita,
Kuniomi Ogata,
Wataru Shimizu,
Miki Yokokawa,
Shiro Kamakura,
Kunio Miyatake, Keiji Tsukada,
Satsuki Yamada,
Shigeyuki Watanabe,
Iwao Yamaguchi
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ABSTRACT: The objective of this study is to use magnetocardiography to determine the existence of a small abnormal current during ventricular depolarization in patients with Brugada syndrome. To understand this small difference in abnormal current during ventricular depolarization, we compared abnormal currents of patients with cases of complete right-bundle-branch block (CRBBB).
We developed a whole-heart electrical bull's eye map (WHEBEM) that uses magnetocardiograms (MCGs) to visualize the current distribution in a circular map. MCGs of Brugada syndrome patients (n = 16), CRBBB patients (n = 10), and controls (n = 12) at rest were recorded. In the WHEBEMs of Brugada syndrome patients, the magnitude of the S-wave current in the upper-right direction of the anterior side is larger than that of the controls. In addition, the R-wave current direction is similar to that of the controls, and the R-wave vector is distributed over a larger area than that of the controls. On the other hand, the CRBBB patients have a distribution of R-wave currents over a larger area in the left anteromedian region and the left posteromedian region. Moreover, in all CRBBB patients, S-wave currents with a large magnitude have the same direction distributed over a small area.
The WHEBEM findings suggest that there is an abnormal current in the direction to the upper right (in the S-wave) in the anterosuperior region of Brugada syndrome patients. We thus conclude that a WHEBEM has the potential to detect characteristics of heart disease.
Pacing and Clinical Electrophysiology 01/2007; 29(12):1359-67. · 1.35 Impact Factor
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AKIHIKO KANDORI Ph.D,
TSUYOSHI MIYASHITA M.S,
KUNIOMI OGATA M.S,
Ph.D. WATARU SHIMIZU M.D,
MIKI YOKOKAWA M.D,
Ph.D. SHIRO KAMAKURA M.D,
Ph.D. KUNIO MIYATAKE M.D,
KEIJI TSUKADA Ph.D,
Ph.D. SATSUKI YAMADA M.D,
Ph.D. SHIGEYUKI WATANABE M.D, [......],
TSUYOSHI MIYASHITA,
KUNIOMI OGATA,
WATARU SHIMIZU,
MIKI YOKOKAWA,
SHIRO KAMAKURA,
KUNIO MIYATAKE, KEIJI TSUKADA,
SATSUKI YAMADA,
SHIGEYUKI WATANABE,
IWAO YAMAGUCHI
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ABSTRACT: Background: The objective of this study is to use magnetocardiography to determine the existence of a small abnormal current during ventricular depolarization in patients with Brugada syndrome. To understand this small difference in abnormal current during ventricular depolarization, we compared abnormal currents of patients with cases of complete right-bundle-branch block (CRBBB).Methods and Results: We developed a whole-heart electrical bull's eye map (WHEBEM) that uses magnetocardiograms (MCGs) to visualize the current distribution in a circular map. MCGs of Brugada syndrome patients (n = 16), CRBBB patients (n = 10), and controls (n = 12) at rest were recorded. In the WHEBEMs of Brugada syndrome patients, the magnitude of the S-wave current in the upper-right direction of the anterior side is larger than that of the controls. In addition, the R-wave current direction is similar to that of the controls, and the R-wave vector is distributed over a larger area than that of the controls. On the other hand, the CRBBB patients have a distribution of R-wave currents over a larger area in the left anteromedian region and the left posteromedian region. Moreover, in all CRBBB patients, S-wave currents with a large magnitude have the same direction distributed over a small area.Conclusions: The WHEBEM findings suggest that there is an abnormal current in the direction to the upper right (in the S-wave) in the anterosuperior region of Brugada syndrome patients. We thus conclude that a WHEBEM has the potential to detect characteristics of heart disease.
Pacing and Clinical Electrophysiology 11/2006; 29(12):1359 - 1367. · 1.35 Impact Factor
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ABSTRACT: Fetal magnetocardiography (fMCG) is useful for analysis of fetal cardiac events. However, fetal presentation and movement affect the fMCG waveform, making it difficult to standardize the waveform. The aim of this study was to investigate whether the use of vector magnetometers can compensate for these limitations. We studied 59 fetuses (gestational age, 22-40 wk, median, 32), including 41 with uncomplicated pregnancies and 18 with fetal cardiac disease. fMCG was recorded twice in each case, and the two waveforms were compared with each other in uncomplicated subjects to investigate the effects of fetal presentation. The superconducting quantum interference device (SQUID) system used in this study was a 12-channel vector magnetometer, by which the three components of the magnetic field (Bx, By, Bz) could be detected simultaneously at four recording points. By constructing the three components, a composite waveform (Bxyz) was obtained. The configuration of the composite waveforms was similar among normal fetuses always with positive polarity, independent of fetal presentation and movement. The difference in the time intervals (PR, QRS, and ventricular activation time [VAT]) between the first and second measurements was minimal in the composite waveforms (Bxyz) compared with that in each channel (Bx, By, Bz). Even before signal averaging, waveforms with high time resolution were recorded in at least one of the three components, making it possible to analyze fetal arrhythmias precisely. Our results indicate that vector magnetocardiography is potentially useful for standardization of the fMCG waveforms and to provide a more complete and accurate analysis of fetal arrhythmias.
Pediatric Research 02/2006; 59(1):121-5. · 2.70 Impact Factor
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Akihiko Kandori,
Tsuyoshi Miyashita,
Kuniomi Ogata,
Wataru Shimizu,
Miki Yokokawa,
Shiro Kamakura,
Kunio Miyatake, Keiji Tsukada,
Satsuki Yamada,
Shigeyuki Watanabe,
Iwao Yamaguchi
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ABSTRACT: Both ventricular depolarization abnormalities (QRS complex) and repolarization ones (ST/T) are still controversial in literature. The objective of this study was to clarify the space-time variations that occur in patients carriers of Brugada syndrome using Magnetocardiography and also compare them with cases of complete right-bundle branch block (CRBBB) and individuals without any dromotropic disorder (control group).
Magnetocardiograms (MCGs) of Brugada syndrome patients (n = 16), CRBBB patients (n = 14), and members of a control group (n = 46) at rest were recorded. The MCGs were used to produce a whole-heart electrical-activation diagram (W-HEAD), which can visualize the spatial time-variant activation in the whole heart. In the W-HEAD pattern, three activations were located in the left ventricle, and CRBBB patients had a wide peak with about 65-ms delay on the right anterior side. While the Brugada syndrome pattern has a posteromedian left-ventricle excitation, that is half the amplitude that occurs in CRBBB patients, the electrical conduction rate to the posterosuperior septum area was low.
The W-HEAD data made it possible to visualize space-time depolarization abnormalities. These findings suggest that the electrical conduction rate to the posterosuperior septum area in Brugada syndrome cases is low, and this low activation may be a feature of typical Brugada syndrome.
Pacing and Clinical Electrophysiology 02/2006; 29(1):15-20. · 1.35 Impact Factor
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Journal of Cerebral Blood Flow & Metabolism 07/2005; · 5.01 Impact Factor
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Keiji Enpuku,
Katsuhiro Inoue,
Kohji Yoshinaga,
Akira Tsukamoto,
Kazuo Saitoh, Keiji Tsukada,
Akihiko Kandori,
Yoshinori Sugiura,
Shigenori Hamaoka,
Hiroyuki Morita,
Hiroyuki Kuma,
Naotaka Hamasaki
IEICE Transactions. 01/2005; 88-C:158-167.
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ABSTRACT: To develop a new measurement tool for quantitatively detecting the finger movement of a patient with Parkinson's disease (PD), we designed a magnetic sensing system consisting of a magnetic induction coil, a sensing coil, and a circuit unit. The sensing coil detects the inducted magnetic field that varies with the distance between the two coils, and the detected signals are demodulated in the circuit unit in order to obtain the variation voltage from the oscillation frequency. To obtain a coefficient for converting voltage to distance, we measured the output voltages for seven fixed finger positions of 12 normal volunteers. The voltage differences corresponding to the finger movement in 20 PD patients, six age-matched controls, and 12 normal volunteers were then recorded for 30s. To investigate the velocity and acceleration of the finger movement, we calculated their waveforms from the measured displacement waveform. We also detected the main frequency of the tapping rhythm by using a fast Fourier transform (FFT). The averaged amplitude of each waveform decreased with the disorder in the Hoehn-Yahr (HY) stage, while the averaged tapping frequency of PD patients did not have any correlation with this stage. It can be concluded that this magnetic sensing system can assess finger movement quantitatively.
Neuroscience Research 07/2004; 49(2):253-60. · 2.25 Impact Factor
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ABSTRACT: A method for reconstructing an action potential during the repolarization period was developed. This method uses a current distribution-plotted as a current-arrow map (CAM)--calculated using magnetocardiogram (MCG) signals. The current arrows are summarized during the QRS complex period and subtracted during the ST-T wave period in order to reconstruct the action-potential waveform. To ensure the similarity between a real action potential and the reconstructed action potential using CAM, a monophasic action potential (MAP) and an MCG of the same patient with type-I long-QT syndrome were measured. Although the MAP had one notch that was associated with early afterdepolarization (EAD), the reconstructed action potential had two large and small notches. The small notch timing agreed with the occurrence of the EAD in the MAP. On the other hand, the initiation time of an abnormal current distribution coincides with the appearance timing of the first large notch, and its end time coincides with that of the second small notch. These results suggest that a simple reconstruction method using a CAM based on MCG data can provide a similar action-potential waveform to a MAP waveform without having to introduce a catheter.
Physics in Medicine and Biology 06/2004; 49(10):2103-15. · 2.83 Impact Factor
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ABSTRACT: Double-D-shaped high-Tc superconducting loops were used to form an open-ended, cylindrical magnetic shield for biomagnetic measurements. The total magnetic flux through such a superconducting loop stays constant; thus, the loop can shield a cylindrical magnetic shield from an external magnetic field that penetrates into it from its open ends. The high-Tc superconducting loops are made of Bi2Sr2Ca2Cu3Ox tape wire, and the cylindrical magnetic shield is made of flexible magnetic sheets composed of Fe–Cu–Nb–Si–B nanocrystalline alloy. Both axial and transverse magnetic field noise in the shield were measured with high-Tc superconducting quantum interference devices. These measurements indicate that the double-D-shaped high-Tc superconducting loops at each open end of a cylindrical magnetic shield reduce not only axial but also transverse magnetic field noise in the magnetic shield. © 2004 American Institute of Physics.
Review of Scientific Instruments 03/2004; 75(4):896-899. · 1.37 Impact Factor
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ABSTRACT: A compact, light and easy-to-handle magnetocardiograph (MCG) has been developed. The MCG consists of a sensor array with superconducting-quantum-interference-device magnetometers made of a high-critical temperature superconductor, arranged in a 4 × 4 matrix, and operated in a vertical magnetically shielding cylinder (1.7 m high and 1 m in diameter). Each magnetometer is paired with each of its adjacent magnetometers, and the difference between the respective outputs provides us with a measure of magnetic gradient. This configuration for the electronic gradiometers cancels out the environmental magnetic field noise within the shielding cylinder. We use the data from the multiple gradiometers to construct a current arrow map that describes the distribution of original current vectors in the area being measured.We used the fabricated MCG to record magnetocardiograms of healthy volunteers. The smallest signals, i.e., the P-waves, were clearly detected without averaging. The current arrow maps obtained from the single-beat magnetocardiograms indicate the feasibility of clinical application of this MCG.
Superconductor Science and Technology 11/2003; 16(12):1383. · 2.66 Impact Factor
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ABSTRACT: The aim of this study was to investigate neural activity during period of vertiginous sensation, induced by caloric stimulation. After caloric vestibular stimulation (CVS) by cold water of five volunteers (n=5, age: 30+/-10), auditory evoked magnetic fields (AEFs) during the subsequent period of vertiginous sensations were measured by magnetoencephalography (MEG). Current-arrow maps (CAMs) were produced to estimate the spatial current distribution of the AEF responses, and a rotation value (dI(rot)) was calculated from the CAM. The worth of the dI(rot) values as indicators of vertigo was evaluated by comparing them with earlier reported values for elderly control (n=11, age: 67+/-5) and chronic dizziness (CD) (n=27, age: 68+/-8) groups (obtained from AEF responses with no the CVS). Although all volunteers felt vertigo during the AEF measurements, the AEF waveforms and CAM pattern only showed slight changes. While the dI(rot) values (1.43+/-0.73) just after CVS were not significantly different from those (1.59+/-0.46) for the elderly controls, they were significantly different from those (3.54+/-1.34) for the CD patients. These findings suggest that (i) the new parameter (dI(rot)) is more sensitively indicates dizziness (non-rotatory sensation) than vertigo (ii) the auditory cortical region may play an important role in body-balance perception of floating sensations.
Neuroscience Research 08/2003; 46(3):281-8. · 2.25 Impact Factor
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ABSTRACT: A magnetocardiograph, consisting of superconducting quantum interference device (SQUID) magnetometers made of a high-critical-temperature (T<sub>c</sub>) superconductor and a compact magnetically shielding cylinder, has been developed. We assembled a sensor array of 4×4-matrix-arranged magnetometers which are treated as 24 electronic first-order gradiometers by taking the differences between the outputs in every pair of adjacent magnetometers. Field gradients generated by P waves were estimated from the results for 21 subjects of a conventional magnetocardiograph made of low- T<sub>c</sub> SQUID gradiometers. Every gradiometer of the assembled sensor array was then designed to be sufficiently sensitive to detect the field gradient corresponding to the mean P wave. The clear magnetocardiograms obtained without averaging indicate the clinical applicability of the developed magnetocardiograph. © 2003 American Institute of Physics.
Applied Physics Letters 07/2003; · 3.84 Impact Factor
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ABSTRACT: A stabilizer for superconducting quantum interference device (SQUID) magnetometers operating in lightly shielded environments is proposed. When the stabilizer is applied in an electrical gradiometer, which operates by obtaining differences between the outputs of the two SQUID magnetometers, the intrinsic noise of the stabilizer can be neglected. The operation of an electrical gradiometer where the SQUID magnetometers are of the high-critical-temperature (high-Tc) type is shown to be substantially more stable in a lightly magnetically shielding cylinder with the addition of the stabilizer function. Very clear magnetocardiograms were obtained by a gradiometer of this type. © 2003 American Institute of Physics.
Applied Physics Letters 05/2003; 82(18):3059-3061. · 3.84 Impact Factor
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ABSTRACT: We have previously developed current vector maps of tangential components on the magnetocardiogram (MCG) to obtain cardiac current distribution images. The present study was conducted to detect repolarization abnormalities in patients with cardiomyopathy using the current vector map.
Thirteen patients with cardiomyopathy (nine males and four females aged 7-16 years, mean, 11.5 +/- 3.1 years, +/- SD), and 15 age- and sex-matched normal subjects were studied. Normal components (Bz) of MCG were measured at rest with a multi-channel superconducting quantum interface device (SQUID) system, and differentiated in the tangential direction to obtain current vector maps. Homogeneity of current in the heart during repolarization was investigated. The direction of the maximum current vector was also calculated in each case.
In all normal subjects, the current vector consistently showed a left downward direction on the frontal chest plane during the repolarization process. On the other hand, 8 out of 13 patients with cardiomyopathy showed different patterns; four of these patients showed multi-dipoles, and the other four showed a shift in the current vector direction. One of the eight cases showed no abnormality on electrocardiogram (ECG).
Repolarization process in patients with cardiomyopathy was apparently different from those in normal subjects on the current vector map. It was easy to visualize the repolarization process as a projection to the frontal plane, including regional abnormalities, by the current vector maps, which might be more useful for early detection of repolarization abnormalities than ECG.
The International Journal of Cardiovascular Imaging 05/2003; 19(2):163-70. · 2.29 Impact Factor
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ABSTRACT: Magnetocardiography (MCG) is a non-contact mapping technique to record cardiac action currents. The Master's two-step electrocardiogram (ECG) test is a simple exercise method for screening coronary artery disease (CAD), but it is inadequate concerning the sensitivity. Our aim was to develop a new screening method using multichannel MCG instead of ECG.
Thirty subjects (aged 54 +/- 16 years, 27 males), 17 of whom had CAD confirmed by coronary angiography, underwent the Master's exercise ECG test. After the exercise, MCG signals were acquired every minute during recovery with a 64-channel MCG system (MC-6400, Hitachi Ltd). We integrated tangential components of the MCG signals within QRS (during 20, 40, 80, and 120 ms centering on R-wave peak) immediately after exercise (Iex) and 5 minutes after exercise (Irec). The exercise-induced change of currents [(Iex-Irec)/Irec] was determined and normalized for each channel, and the maximal change among 64 channels, maximal QRS integral change, was used as a diagnostic index for myocardial ischemia.
The maximal QRS integral change during 40 ms was significantly higher in the CAD group than in the control group (0.81 +/- 0.51 vs. 0.36 +/- 0.19, p < 0.01). A sensitivity and specificity for predicting CAD by the change > 0.44 were 82 % and 85 %, respectively, yielding a diagnostic accuracy of 83 %. The conventional Master's ECG test identified the CAD patients with a diagnostic accuracy of 63 % (sensitivity 47 %, specificity 85 %).
The Master's two-step exercise test with a 64-channel MCG system showed the high diagnostic accuracy, despite of non-contact recording and simple exercise. The magnetic field in the depolarization process has the potential to detect the subtle myocardial ischemia induced by exercise.
Archiv für Kreislaufforschung 03/2003; 98(2):124-32. · 7.35 Impact Factor
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ABSTRACT: A 59-year-old woman with partial atrial standstill was studied using magnetocardiograms (MCGs), which revealed through QRS-T subtraction and time-frequency analysis that there was a high-frequency (6 Hz) magnetic source at the low atrial septum. MCGs are useful for noninvasively evaluating the clinical course of patients with atrial fibrillation.
Circulation Journal 01/2003; 66(12):1178-80. · 3.77 Impact Factor
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ABSTRACT: A long-lasting dizzy sensation is a common complaint in elderly subjects. The pathogenesis and effective treatment of such chronic dizziness (CD), however, have not yet been fully elucidated because of lack of methods for evaluating this sensation. On the basis of assumption that CD may be attributable partly to cortical functional abnormality, we attempted to estimate the function of auditory cortex by measurements of auditory-evoked magnetic fields (AEFs). Magnetic field signals in the parieto-temporal cortex were evoked by 1000-Hz tone-burst with 90-dB normal hearing level sounds, and the highest-amplitude magnetic waveforms at approximately 100-ms (N100m) were analyzed as electrical current arrows in normal subjects (n=11), patients with CD (n=27) and patients with cerebral infarction but no dizzy sensation (n=9). In the normal subjects, the current arrows pointed to a nearly straight line with small directional distortion as indicated by a rotation-degree parameter, dI(rot) of 1.59+/-0.46. In 17 of 27 CD patients, the directions of current arrows were markedly distorted showing abnormally high dI(rot) values greater than 2.50 (the mean plus two standard deviations of normal values) and disclosed a clockwise or counter-clockwise rotation in either side or both sides of parieto-temporal cortex. In all the patients with cerebral infarction, the current arrows exhibited the similar pattern as the normal subjects. None of them exhibited abnormally high dI(rot) values. We hypothesized that the rotational abnormality may be caused by abnormal neuronal excitation, since non-evoked magnetic fields in temporal lobe epilepsy demonstrated the similar current rotational abnormality as reported previously. Seven CD patients were treated with anticonvulsants, and four showed remarkable amelioration of dizzy sensation. In all the four patients with symptomatic amelioration, the disappearance of rotational abnormality in AEFs or the tendency towards disappearance was observed following symptomatic amelioration. The results of the present study suggest that the auditory center may contribute to the maintenance of equilibrium, and its dysfunction may lead to the development of CD. AEFs measurements may make it possible to evaluate the functional abnormality of auditory center and may be useful for studying the pathophysiology and treatment of CD.
Brain Research 01/2003; 957(2):373-81. · 2.73 Impact Factor
