Activities of NIMD
Information on MEG Center
The MEG Center was established at Minamata City General Hospital & Medical Center in 2009 to investigate an objective evaluation method for methylmercury poisoning. MEG stands for magnetoencephalography, which is a noninvasive technique for examining brain activity. The MEG Center conducts up-to-date examinations for patients with Minamata disease and elderly people in Minamata disease-affected areas and provides health counseling, including lifestyle counseling, based on the results of these examinations. In addition, the “Study Group on Improvement of Minamata Disease Treatment” was established at the National Institute for Minamata Disease to conduct research on latest treatment methods to improve the symptoms of Minamata Disease.
Objective Methods for Evaluating Minamata Disease
The symptoms of Minamata disease include sensory disturbances, concentric constriction of the visual fields, and ataxia. We are now able to objectively evaluate to some extent the abnormalities in the primary somatosensory cortex using MEG, and atrophy of the cerebellum and thalamus using magnetic resonance imaging (MRI). Using these indices, we aimed to establish an optimal method for the objective assessment of Minamata disease.
MEG
MEG is a device that records brain activity by measuring small magnetic fields generated by the brain in real time. An objective assessment of sensory dysfunction was performed by measuring the somatosensory evoked magnetic fields (SEFs) produced by stimulating the median nerve at the wrist. Sensory dysfunction is seen in many patients with Minamata disease, but it can be caused by a variety of other factors. Therefore, whether it is due to methylmercury needs to be fully investigated, including other neurological findings.
What an MEG test can tell us
A small electric current flows in the active part of the brain, generating magnetism. An MEG test can accurately capture the status of brain activity by measuring the magnetic fields that are generated.
While the N20m is always present in normal individuals, it is diminished or absent in patients with Minamata disease, and the waveform is not constant; therefore, this measurement provides an objective assessment of sensory disturbance.
Brain MRI scan
MRI can measure brain morphology and the degree of brain atrophy by evaluating the density and volume of each brain region. In addition, the MEG Center uses the latest MRI technology to conduct examinations, which enables performing corrections even when the patient is moving. This is expected to reduce the burden of examination for patients with Minamata disease whose bodies are subject to movement.
What a brain MRI scan can tell us
The cerebellum and thalamus were significantly atrophied in patients with Minamata disease. In addition, the latest MRI technology can be used to evaluate nerve fibers in the brain, which shows that nerve fibers are reduced in the cerebellum and thalamus of patients with Minamata disease.
Based on these results, the cerebellum and thalamus were determined to be useful in MRI to discriminate between patients with Minamata disease and healthy individuals .
By combining MEG and brain MRI, the sensitivity (probability of correctly identifying a person with the disease as having the disease) was approximately 80% and the specificity (probability of correctly identifying a person without the disease as not having the disease) was approximately 90%.
Information regarding inspections
We are seeking people willing to participate in our research on objective assessment methods for Minamata disease. We also offer health counseling to those with concerns regarding brain function by performing the latest tests.
- Inspection flow
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- Inspection time:
- Approximately 2 h. *Recommended to take a restroom break or other breaks.
- Subjects:
- Those born before 1970 in Minamata City or its suburbs
- Test Results:
- Detailed explanations and lifestyle guidance for dementia prevention will be provided later at the MEG Center.
*Precautions
- ・To eliminate the effects of magnetism, all metal objects are required to be removed.
- ・Since there are instances where you may not be able to take the test, we will confirm your medical history when you apply.
Treatment research
Of the symptoms of Minamata disease, spasticity (muscle spasms in the limbs) and neuropathic pain (pain caused by nerve damage) have not been effectively treated and cause a significant decline in daily activities of patients with Minamata disease. Recently, magnetic stimulation therapy has attracted attention as an effective treatment for these symptoms, and the MEG Center has performed research on magnetic stimulation therapy for neuropathic pain. In addition, botulinum therapy for spasticity is being conducted in cooperation with Okabe Hospital.
Magnetic stimulation therapy
This treatment does not require surgery but stimulates the brain almost painlessly by applying magnetism generated by magnetic coils to the brain, thereby relieving symptoms. Magnetic stimulation of the motor cortex, an area of the brain involved in controlling movement on the side opposite to the site of pain, is thought to reduce neuropathic pain.
Navigation Systems
In magnetic stimulation therapy, it is important to apply magnetism precisely to the treatment area. The MEG Center uses a “navigation system” to precisely apply magnetic stimulation to the motor cortex.
Effects of magnetic stimulation therapy
- Neuropathic pain is expected to reduce.
- Magnetic stimulation therapy before rehabilitation can increase rehabilitation effectiveness.
There have been many reports on the effectiveness of magnetic stimulation therapy for neuropathic pain; however, it is currently not approved by health insurance. This research is approved by the authorized clinical research review committee (Kyushu University Certified Institutional Review Board for Clinical Trials) as stipulated by the “Clinical Trials Act.”
Botulinum
Spasticity can be reduced closer to normal levels by injecting a drug called botulinum toxin, which suppresses the action of nerves that contract the muscles.
Effects of botulinum therapy
- The muscles of the arms and legs become softer and easier to move, making it easier to perform daily activities.
- Movement of the body and rehabilitation become easier.
- Prevents the joints from becoming stiff and difficult to move, and from becoming deformed.
- Pain caused by spasticity can be relieved by relieving limb spasticity.
- The burden of caregiving will be lightened.
- By relieving the strong tension in the muscles around the neck and shoulders, the head can be positioned closer to its normal position.
Treatment
Magnetic Stimulation Therapy
*We have currently suspended applications for magnetic stimulation therapy.
Botulinum treatment
- Treatment time:
- Approximately 30 min.
- Treatment process:
- If botulinum treatment is applicable, referral will be made to Okabe Hospital.
- Subjects:
- People with stiff hands and feet
- Evaluation:
- Examination of the degree of stiffness and range of joint motion before and after treatment.
Other treatments include spinal cord stimulation therapy for neuropathic pain that does not respond to magnetic stimulation, intrathecal baclofen therapy for spasticity, and deep brain stimulation therapy for tremors. At the National Minamata Disease Research Center, only magnetic stimulation and botulinum therapy are provided. For other treatments, referrals are made to specialists in the “Study Group on Improving the Treatment of Minamata Disease.”
Please consult your primary care physician for further information. Please contact us at the following address if you do not have a primary care physician:
Please contact us for inquiries about examination and treatment.
Comprehensive Medicine Section, Department of Clinical Medicine
TEL: +81-966-63-3111