[Secondary degeneration of the substantia nigra after cerebral infarctions including the striatum].

Secondary degeneration of the substantia nigra (SN) after damage to the ipsilateral striatum has been widely reported in animal stroke models. Secondary degeneration of the SN frequently occurs in stroke patients with damage to the striatum. Decreased γ-aminobutyric acid in the striatonigral pathway causes disinhibition of the SN pars reticulata, which consequently causes neuronal degeneration there. The SN pars compacta, in constant, degenerates in a retrograde manner. Diffusion-weighted imaging reveals this secondary degeneration as a high-intensity lesion, which may be misdiagnosed as a new infarction.