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The main pathological characteristic of Parkinson's disease is cell death in the substantia nigra. In particular, this death occurs in the ventral part of the pars compacta, with up to 70% of the cells affected by the time the patient dies. [2] The mechanisms by which the brain cells are lost are varied. [3]
The substantia nigra (SN) is a basal ganglia structure located in the midbrain that plays an important role in reward and movement. Substantia nigra is Latin for "black substance", reflecting the fact that parts of the substantia nigra appear darker than neighboring areas due to high levels of neuromelanin in dopaminergic neurons. [1]
The loss of dopamine-producing neurons in the substantia nigra initially presents as movement abnormalities, leading to Parkinson's further categorization as a movement disorder. [1] In 30% of cases, disease progression leads to the cognitive decline known as Parkinson's disease dementia (PDD). [ 7 ]
Post-encephalitic parkinsonism is a disease believed to be caused by a viral illness that triggers degeneration of the nerve cells in the substantia nigra. Overall, this degeneration leads to clinical parkinsonism .
Face of the giant panda sign; Axial T2-weighted MRI of the brain at the level of the midbrain showing the characteristic ‘face of the giant panda’ sign, with normal red nuclei and substantia nigra (pars reticulata) against a background of hyperintensity in the tegmentum, as well as hypointensity of the superior colliculi
Parkinson's disease (PD) is a chronic neurodegenerative disorder caused by the progressive degeneration of dopamine-producing neurons in the substantia nigra, a structure located in the midbrain essential for reward and movement. The rapid deterioration of these dopaminergic neurons leads to both motor and non-motor complications.
The substantia nigra is located in the ventral midbrain of each hemisphere. It has two distinct parts, the pars compacta (SNc) and the pars reticulata (SNr). The pars compacta contains dopaminergic neurons from the A9 cell group that forms the nigrostriatal pathway that, by supplying dopamine to the striatum, relays information to the basal ganglia.
Diagnosis might be suggested by the combination of developmental delay, epilepsy, and no satiety response. [8] A pattern of abnormality on MRI brain scans shows early swelling of the basal ganglia (globus pallidus and substantia nigra) and dentate nucleus , with later accumulation of iron in the globus pallidus and substantia nigra. [ 9 ]