PURPOSE

This document presents a simplified and clinically practical definition of Myalgic Encephalomyelitis (M.E.) and Chronic Fatigue Syndrome (CFS). It aims to improve understanding of these conditions by focusing on measurable, testable criteria and by highlighting the multi‑system nature of the illness.

KEY POINTS

1. Multi‑System Illness

• M.E. is not a single isolated disease but involves multiple body systems working together.
• The condition reflects a complex interaction of physiological changes across the body.

2. Testable Clinical Criteria

• The definition emphasises the importance of measurable and observable symptoms.
• It aims to provide criteria that can be clinically evaluated rather than relying purely on subjective reporting.

3. Central Role of Brain Dysfunction

• Diffuse brain injury is identified as a core feature of M.E
• Neurological effects include cognitive and neuropsychological changes.

4. Key Symptom Areas

The illness includes a range of overlapping dysfunctions:

• Sleep Dysfunction
  • Unrefreshing sleep and major sleep disturbances are central features.
• Muscle Dysfunction
  • Muscle weakness and pain are common and significant symptoms.
• Cardiovascular Issues
  • Involvement of vascular and cardiac systems is recognised.
• Endocrine Dysfunction
  • Hormonal regulation problems may play a role.

5. Phases of Illness

• The illness often develops in two stages:
  1. Initial infection phase
  2. Long‑term chronic phase

6. Whole‑Body Assessment Approach

• Diagnosis should consider the entire body rather than focusing on isolated symptoms
• “Total body mapping” is suggested to fully understand the condition.

7. Contributing Factors

• Genetic background and personal medical history may influence development and progression.

TARGET AUDIENCE

• Medical professionals and clinicians
• Researchers studying M.E. and CFS
• Patients and caregivers seeking a clearer understanding of the condition
• Health organisations and policymakers

OVERALL OUTCOME

This definition provides a clearer, more structured framework for understanding M.E. and CFS as complex, multi‑system conditions. It supports improved diagnosis and management by emphasising measurable criteria, whole‑body evaluation, and the interaction of neurological, physiological, and systemic factors.