Dysarthria and apraxia of speech associated with FK-506 (Tacrolimus)

The immunosuppressive agent FK-506 (tacrolimus) is one of the agents most commonly used to prevent rejection after liver transplantation. Neurologic toxicity related to FK-506 has been reported, including speech disorders; however, a detailed analysis of the speech disorder associated with use of FK-506 has not been presented. Herein we describe a patient who exhibited mutism, then severe apraxia of speech with a concomitant hypokinetic, spastic, and ataxic dysarthria after administration of FK-506. His re-sidual mixed dysarthria, without radiographie evidence of a structural lesion, suggests dysfunction of one or more neurochemical systems. The pathophysiologic mechanisms underlying this intriguing entity remain obscure.