Hyperkinetic Movement Disorders Induced by Mirtazapine: Unusual Case Report and Clinical Analysis of Reported Cases

Abstract

Background: Hyperkinetic movement disorders caused by mirtazapine are very rarely reported, and involuntary severe cervical and truncal dystonia as an initial manifestation of mirtazapine-induced hyperkinetic movement disorder have not yet been reported. This study aimed to report an unusual case and to investigate the clinical pattern of mirtazapine-induced hyperkinetic movement disorder. Methods: We present a patient with involuntary severe cervical and truncal dystonia as an initial manifestation of mirtazapine-induced hyperkinetic movement disorders. Additionally, we review previously reported cases and analyse the clinical pattern of mirtazapine-induced hyperkinetic movement disorders. Results: Among 12 cases including our case, the main features of hyperkinetic movement symptoms induced by mirtazapine are akathisia (n=5, 42%) and dystonia (n=4, 33%). The other movement symptoms were dyskinesia (n=2, 17%) and periodic limb movement disorder (PLMD)-like nocturnal movements (n=1, 8%). Major associated conditions were older patients with depression or previous medication history of multiple neuropsychiatric drugs. Conclusion: The results of this clinically investigative study may provide support for the diagnosis of mirtazapine-induced hyperkinetic movement disorders. In addition, if there are hyperkinetic movement symptoms in older depressive patients taking psychiatric medications, including mirtazapine, a diagnosis of drug-induced hyperkinetic movement disorder caused by mirtazapine should be considered, and cessation of mirtazapine should be implemented as the best treatment of choice.