Mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS)

1) Disease Description (Causes and Symptoms)

• Definition: Motor neuron disease (MND) refers to a group of degenerative diseases in which the upper- and lower-limb motor neurons (upper and lower motor neurons) in the brain and spinal cord are progressively damaged, resulting in muscle weakness and muscle atrophy.
• Causes/Pathophysiology: The exact cause is unknown, and interactions among multiple mechanisms—including genetic predisposition, excitotoxicity, oxidative stress, immune mechanisms, infection, and microtubule abnormalities—are suspected. The incidence usually increases after age 40 and is more common in men. Some cases are associated with a family history.
• Main symptoms:
  • Muscle weakness and muscle atrophy (gradual weakening of the limbs)
  • Muscle cramps (including claudication) and fasciculations (muscle twitching)
  • Weight loss and reduced muscle mass
  • Dysphagia (difficulty swallowing) and frequent choking
  • Shortness of breath (especially during sleep and worsening when lying down) — progresses due to weakness of the diaphragm/respiratory muscles
  • Weak cough and increased risk of pneumonia
• Diagnostic points: A detailed medical history and neurological examination; confirmation of evidence of upper- and lower-limb motor neuron damage through electrophysiology (electromyography/nerve conduction studies); exclusion of other causes with MRI; and muscle biopsy if necessary. Diagnosis is made based on a combination of clinical, electrophysiological, and imaging findings.
• Prognosis (summary): Although the course varies, one report states that approximately 20% of all patients survive up to 5 years after diagnosis. As the disease progresses, the risk of death from respiratory failure is high.

2) Treatment Methods and Precautions

• Definitive treatment: There is currently no cure. The main approach is drug treatment aimed at slowing progression and management of symptoms and complications.
  • Medications:
    • Riluzole: The only drug clinically proven to extend survival by several months (the effect is limited).
    • Edaravone: Evidence has been reported that it slows the rate of functional deterioration in some patient groups (the indications and availability depending on insurance and region need to be confirmed).
  • Respiratory management:
    • Regular monitoring of pulmonary function (particularly vital capacity in the sitting and lying positions, maximum expiratory/inspiratory pressure, etc.).
    • Noninvasive ventilation (NIV, such as mask-based ventilation) helps improve respiratory symptoms and prolong survival.
    • Ongoing respiratory support (mechanical ventilation) should be decided based on the goals and quality of life of the patient and family.
  • Nutrition and swallowing management:
    • If dysphagia progresses, PEG (percutaneous endoscopic gastrostomy) should be considered to ensure adequate intake and reduce the risk of aspiration.
    • Consultation with a dietitian (high-calorie, high-protein diet and changes in the method of intake).
  • Rehabilitation and assistive devices:
    • Physical and occupational therapy to maintain joint mobility, and provision of walking aids, wheelchairs, and assistive devices for daily living.
    • Speech therapy (swallowing training and communication assistive devices).
  • Symptom treatment and supportive care:
    • Medications to relieve pain and cramps, secretion management, emotional and psychological support, and referral to hospice and palliative care.
  • A multidisciplinary team approach is recommended: coordinated care with neurology, pulmonology, rehabilitation medicine, nutrition, speech therapy, clinical genetics, social work, clinical trial centers, and others.
• Precautions/Complication risks:
  • Increased risk of pulmonary infection (aspiration pneumonia) and respiratory failure — immediate evaluation is necessary if respiratory symptoms occur.
  • Malnutrition and weight loss → reduced treatment response and increased risk of infection.
  • Medication side effects (e.g., possible hepatotoxicity from riluzole): liver function tests are necessary.
  • Consider advance planning (such as an advance medical directive) in preparation for reduced communication and decision-making abilities.
• Lifestyle management:
  • Avoid smoking and excessive alcohol consumption, maintain balanced nutrition, and prevent joint contractures through regular exercise and stretching within a tolerable range.
  • Ensure safety at home (slip prevention and mobility assistive devices).

3) Checklist Before an Outpatient Visit (Items to Bring and Preparation)

• Items to bring and prepare:
  • A list of all medications currently being taken (including prescriptions, OTC drugs, and herbal medicines), with doses and times of administration
  • Copies of previous test results (EMG/nerve conduction studies, MRI, blood tests, pulmonary function tests, etc.)
  • Records of recent weight changes (measured weight values)
  • The timing and pattern of symptom onset and progression (when and in which area the weakness began)
  • Records of respiratory symptoms (waking at night, shortness of breath during sleep, weak cough)
  • Whether swallowing problems and aspiration symptoms are present (choking and food frequently getting stuck in the throat)
  • Mobility in daily life (walking distance and whether assistive devices are used)
  • Family history (neurological diseases and hereditary disease history)
  • Questions related to insurance and social support (assistive devices, household support, etc.)
• Organizing in advance the items the doctor is likely to ask about can help make the consultation proceed smoothly.

4) Examples of General Questions to Ask the Doctor

• What are the expected effects and main side effects of this medication (e.g., riluzole or edaravone)?
• How are my current disease stage (rate of progression) and prognosis assessed?
• When would you recommend starting noninvasive ventilation (mask-based) or mechanical ventilation as respiratory function worsens?
• When should nutritional support or a PEG procedure be considered?
• What supportive exercises should I do in daily life, and what activities should I avoid?
• What services are available for connection with multidisciplinary care (rehabilitation, speech therapy, nutrition, and mental health)?
• Is participation in a clinical trial (new drug) possible, or are there any studies you would recommend?

5) Examples of Disease-Specific Questions

• Based on my respiratory function (breathing during sleep, vital capacity, etc.), when would it be appropriate to start noninvasive positive-pressure ventilation (NIV)? What benefits and discomfort can be expected after starting it?
• My dysphagia is gradually worsening. When would you recommend PEG (gastrostomy), and what changes in aspiration risk and nutritional status can be expected with PEG?
• (Optional) If there is a family history: Is evaluation for a familial form (genetic testing) recommended? If so, what genetic tests are usually performed?

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