When stroke occurs in adulthood, mirror movements (MMs; involuntary movements occurring in 1 hand when performing unilateral movements with the contralateral hand) in the paretic hand rarely occur. We present a case of an apparently healthy 54-year-old man presenting with MMs in his left (nondominant) hand. Further evaluation revealed diminished strength and dexterity in left hand, increased spinal excitability, decreased corticospinal excitability, occurrence of ipsilateral motor responses, enlarged cortical motor representation, and imaging findings consistent with a previously undiagnosed right-subcortical stroke. MMs and ipsilateral motor responses may reflect the increased spinal motor neurons' excitability sustained by the spared nonprimary ipsilesional motor areas.
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