The Brain Fatigue Syndrome-Symptoms, Probable Definition, and Pathophysiological Mechanisms.

Fatigue is a common consequence of traumatic brain injury, neurological diseases or developmental disorders, and systemic inflammatory diseases, including autoimmune conditions that affect the brain. This condition is characterized by reduced endurance for cognitive tasks, diminished quality of life, and impaired work capacity. In addition to cognitive difficulties, individuals often experience disproportionately long recovery times after demanding tasks, emotional instability, stress sensitivity, sensory sensitivity, impaired ability to initiate activities, and sleep disturbances. Tension headaches frequently occur when the brain is excessively activated by mental activity. In this paper, we propose the term "Brain Fatigue Syndrome" (BFS) as a collective name for the symptoms closely associated with this pathological fatigue resulting from brain impact. BFS can be identified through interviews and measured using the self-assessment instrument, the Mental Fatigue Scale (MFS). We suggest potential underlying mechanisms at the cellular level for the BFS symptom complex, including astrocyte dysfunction with impaired glutamate signaling and glucose uptake, mitochondrial dysfunction, blood-brain barrier dysfunction, and the activation of microglia and mast cells. In conclusion, BFS suggests a general brain impact. The symptoms associated with BFS typically resolve when the injury or disease heals. However, in some individuals, BFS persists even after the injury or illness has ostensibly healed.