The fundamentals of magnetoencephalography (MEG) were developed and examined in the early 1970's, but it was very laborious to measure the magnetic field emitted from the brain by the MEG systems in those days, because they had fewer channels. A new phase of MEG study has begun with the commercial availability of multi-channel whole-cortex biomagnetometers from the mid 1990's. This new generation of MEGs has enabled us to record whole-cortex activities of a brain all at once (i.e., without repeating the measurements after changing the sensors' position), thus reducing measurement time and increasing measurement precision. This article explain the basic principles of MEG, which are the strength of the brain magnetic field, superconducting quantum interference devices (SQUIDs) and the Josephson Junction (JJ), pick-up coils, the measurement circuit and MEG system together with a recently developed helium circulation system. This article also explains the inverse problem of the measured MEG data, which is difficult, but is essentially important for the future widespread application of MEG. Dipole estimation methods have been commonly used for this, but have a persistent limitation in that they require a heuristic assumption of the dipole number and local minimization. Another approach to estimate dipole distribution by minimizing some performance functions has therefore been developed. This article explains its basic idea and limitations. The article goes on to present some application topics, such as finding the control center of eye accommodation which was identified in the occipito-temporal fissure, typical auditory response and an interesting oddball response which is an automatic auditory brain response to some irregular sounds. Finally, this article explains the time-special resolution of MEG compared with other brain measurement techniques which were already in use and will be explained in this lecture series to clarify the properties of MEG. This article also summarizes present problems which need to be fixed for the future widespread use of MEG.
We studied how individual subject factors that are assumed to be involved in the dizziness symptom induced by the caloric test, such as autonomic imbalance, depressive state, anxious tendency and orthostatic dysregulation (OD) are correlated with dizziness in healthy subjects with normal inner ear function. Subjects who perceived a whirling sensation in the ears after the caloric test showed a significantly increased autonomic symptom score, based on the Graybiel's motion sickness score, as compared to those who perceived a sensation of fluid flowing sideways in the ears. In addition, the duration of nystagmus was significantly longer in the subjects with whirling sensation than in other subjects. The results of psychological testing and interviews revealed a significantly higher depression score as well as higher prevalence of OD in the group with a persistent whirling sensation in both ears as than in the group with a sensation of fluid flowing sideways in both ears, however, there was no significant correlation between the tendency towards autonomic imbalance and anxiety and these sensations in these settings.
Objective: In 1996, we developed an in-hospital vestibular-rehabilitation program for patients with intractable dizziness and have since reported improvements in the quality of life of the rehabilitated patients. This study was aimed at determining the relationship of depression and the state of anxiety to improvement of the quality of life. Methods: The subjects were 100 patients with intractable dizziness, and all were informed that hospitalization was a prerequisite for participation in our program. On admission, the Self-rating Depression Scale (SDS), State-trait Anxiety Inventory (STAI), and Short Form 8 Health Survey (SF-8) were used to evaluate the state of anxiety, depression and the quality of life, respectively. The SF-8 was readministered after 4 weeks. Results: Depression was correlated with the trait of anxiety (R=0.57) as well as with the state of anxiety (R=0.32). Patients were divided into groups depending on their SDS scores. Both the physical component summary (PCS-8) and mental component summary (MCS-8) were equally deteriorated in all patients before admission. The MCS-8 scores were significantly lower in patients with severe depression. After admission, the PCS-8 and the MCS-8 scores improved, but not in the patients with severe depression. Conclusion: Improvement in the quality of life of rehabilitated patients is affected by depression and the state of anxiety. Patients with severe depression and anxiety may require not only physical intervention through our rehabilitation program, but also psychological intervention.
In January 2005, a 31-year-old woman experienced a traffic accident in which her car was struck from behind. With generalized rigidity and vertigo, she was admitted to the orthopedics department of a hospital. Her chief complaints included persistent numbness in all four limbs, a sensation of darkness before the eyes, and occasional bilateral tinnitus. She attempted suicide by slitting her wrists to escape from her severe vertigo, and visited a psychiatric hospital for treatment of the vertigo in April 2005, but treatment failed. She was referred to our department in July 2005. The vertigo was rotatory and non-rotatory and intensified in the period from the evening to night. The patient presented with difficulty in opening her eyes and astasia, as a result of which examination for findings such as nystagmus could not be completed. It was unclear whether these symptoms were attributable to the vertigo or a psychiatric disorder. Caloric testing revealed a right-left difference, which improved over 2 years. The causes of the vertigo were left vestibular dysfunction, somatoform disorder, and atlantoaxial subluxation. In the present case, since the patient was unable to open her eyes and exhibited compulsive symptoms on examination, we considered it difficult to support her coping, so instead we attempted to listen to and be sympathetic with the patient and provide appropriate information and adequate physical care. However, exchange of information among the 7 departments that examined the patient proved inadequate, resulting in failure in determination of diagnosis/treatment strategies and appropriate provision of information to the patient. After the Medical Certificate of Sequelae of a Traffic Accident has been prepared, all medical expenses must be covered by the patient. Establishment of a system in which the Identification Booklet for Physically Disabled People can be issued immediately after a Medical Certificate of Sequelae has been prepared should be considered.
Objectives: Alexithymia is a psychological characteristic involving difficulty expressing and identifying feelings. It has been associated with a variety of psychiatric disorders as well as physical illnesses. The purpose of this study was to investigate the prevalence of alexithymia in patients with vertigo. Methods: The 20-item Toronto alexithymia scale (TAS), the SF-36, the dizziness handicap inventory (DHI), and the state trait anxiety inventory (STAI) were administered to a total of 146 vertigo patients. We also determined any correlation between the length of the disease and alexithymia. Results: Vertigo patients were found to have significantly more alexithymia than controls. There was a positive correlation between TAS and SF-36, DHI and STAI scores in patients with vertigo. A positive correlation between alexithymia and duration of vertigo was found. Conclusion: Alexithymia appears to be related to the progression of vertigo.
Sudden idiopathic sensorineural hearing loss is a frequent diagnosis in cases of acute hearing loss and vertigo. On rare occasions, however, these symptoms in a patient are caused by a cerebrovascular disorder. We describe a patient with hearing loss and vertigo associated with cerebellar infarction. A 68-year-old male with atrial fibrillation and hypertension complained of sudden hearing loss in his right ear and vertigo without any other neurological deficits. The neuro-otological examination revealed severe sensorineural hearing loss, gaze nystagmus, and a saccadic pattern in the eye tracking test. MRI showed an anterior inferior cerebellar territory infarction.