Mirror movements after childhood hemiparesis.

Mirror movements are normal in childhood and may persist to a later age following early brain lesions. We studied these movements in patients with childhood hemiparesis at different ages. The earlier the lesions, the more the mirror movements persisted. More mirror movement persisted in the nonparetic hand than in the paretic one. Complete paralysis of either hand tended to abolish all mirror movements in both hands. The task eliciting the most mirror movement was one that may come under ipsilateral control following contralateral damage. The greater persistence of mirror movements after earlier lesions appears to be an indicator of more extensive compensatory motor system reorganization that takes place after damage to a less mature nervous system.