Which parts of the nervous system are affected by Parkinson disease?

Parkinson disease is a progressive neurological disorder primarily characterized by the degeneration of specific nerve cells within the brainstem, specifically the substantia nigra and the locus ceruleus.1

The pathology involves the following key areas and connections:

• Substantia Nigra: The loss of dopaminergic neurons in this region leads to a significant decrease in dopamine, a neurotransmitter essential for regulating motor function.12
• Basal Ganglia: The substantia nigra maintains critical connections with the basal ganglia, a group of nuclear masses involved in the initiation and patterning of voluntary movement. The deficiency of dopamine disrupts the signaling within this system, leading to the characteristic motor symptoms of the disease.13
• Locus Ceruleus: Along with the substantia nigra, this pigmented nucleus in the brainstem undergoes degeneration.1

While the disease primarily affects these brain regions, experimental therapies have also explored the role of the spinal cord in managing motor symptoms, such as freezing episodes.2