Secondary pallidonigral degeneration mimicking recurrent acute stroke in clinical presentation and magnetic resonance imaging: a case report

BACKGROUND: Secondary pallidonigral transneuronal degeneration after a remote primary cerebral infarct can mimic recurrent stroke at clinical presentation. We describe a patient with secondary pallidonigral degeneration following a previous putaminal infarct, which was diagnosed through diffusion-weighted (DWI) and T2-weighted imaging (T2WI). CASE PRESENTATION: A 64-year-old man complained of an acute relapse of right-lower-limb weakness following a cerebral infarction 2 months before presentation. Recurrent cerebral stroke was initially diagnosed in the emergency room. DWI of the brain revealed a subacute to chronic infarct in the left putamen and new acute cytotoxic edema in the left substantia nigra (SN) and globus pallidus while T2WI also showed hyperintensity in the same regions. The SN was outside the aforementioned middle cerebral arterial territory, which includes the putamen. These findings are compatible with the diagnosis of acute pallidonigral injury secondary to striatal infarction. The patient had fully recovered from his right-lower-limb weakness after 1 month. CONCLUSIONS: Secondary pallidonigral degeneration may mimic recurrent stroke. DWI along with T2WI facilitates elucidation of this clinicopathological entity, and thus unnecessary treatment can be avoided.