GLOSSARY

Neural degeneration (neurodegeneration) is the progressive loss of neuronal structure and function, including neuronal death, occurring in neurodegenerative diseases, nerve injuries, and to some extent in normal ageing.

Common Mechanisms

• Accumulation of misfolded proteins: amyloid-β and tau (Alzheimer’s), alpha-synuclein (Parkinson’s), TDP-43 (ALS), and huntingtin.
• Oxidative stress and mitochondrial dysfunction.
• Neuroinflammation: chronic activation of microglia.
• Excitotoxicity: excessive glutamate.
• Impaired clearance: reduced function of the glymphatic system (especially with sleep loss).

Main Diseases

• Alzheimer’s disease: the most common cause of dementia.
• Parkinson’s disease: loss of dopaminergic neurons.
• ALS: loss of motor neurons.
• Huntington’s disease: genetic; the basal ganglia.
• CTE: linked to repetitive head impacts.

Wallerian Degeneration

After a peripheral axon is cut, the part distal to the cell body degenerates over a few days and is cleared, making way for regeneration.

Modifiable Risk Factors