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Topic

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Substantia nigra

The substantia nigra is a vital structure in the midbrain, notable for its dark pigmentation and key role in motor control and reward pathways. It forms a component of the basal ganglia and is critically involved in the modulation of movement through dopaminergic neurotransmission. Dysfunction or degeneration of the substantia nigra, most notably the pars compacta, is a hallmark of Parkinson’s disease and other movement disorders.

Synonyms

  • Locus niger

  • Black substance

  • Nigral complex

  • Substantia nigra pars compacta (SNc) and substantia nigra pars reticulata (SNr) – subcomponents

Arterial Supply

  • Primarily supplied by branches of the posterior cerebral artery (PCA), particularly the posterior perforating branches (including the paramedian branches).

  • Additional supply from posterior communicating artery and anterior choroidal artery branches.

Venous Drainage

  • Drained by small veins that empty into the basal vein of Rosenthal.

  • Further drainage via the great cerebral vein (vein of Galen).

Function

  • Major source of dopaminergic neurons (especially in the pars compacta).

  • Modulates the basal ganglia circuits responsible for voluntary movement control.

  • Plays a role in reward, addiction, and mood regulation through dopamine release.

  • Involved in ocular movement control (via projections to the superior colliculus).

MRI Appearance

  • T2-weighted: Substantia nigra appears as a hypointense (dark) band due to melanin and iron content, distinguishable from surrounding midbrain.

  • T1-weighted: Typically isointense to slightly hyperintense relative to adjacent brainstem tissue; less distinctly visualized than on T2.

  • FLAIR: Substantia nigra is not prominently visualized; may appear isointense or slightly hypointense.

  • Pathology (e.g., Parkinson’s disease): May show loss of normal T2 hypointensity or atrophy.

CT Appearance

  • Substantia nigra is not well visualized on CT due to lack of contrast from surrounding midbrain.

MRI images

Substantia nigra mri 3t axial image