Drug-induced stuttering: A comprehensive literature review

Abstract

Drug-induced stuttering (DIS) is a type of neurogenic stuttering (NS). Although DIS has not been reported as frequently as other cases of NS in the literature, it is not a negligible adverse drug reaction (ADR) which can significantly affect the quality of life if not treated. This literature review aims to evaluate the epidemiological and clinical characteristics of DIS and suggests some pathophysiological mechanisms for this ADR. Relevant English-language reports in Google Scholar, PubMed, Web of Science, and Scopus were identified and assessed without time restriction. Finally, a total of 62 reports were included. Twenty-seven drugs caused 86 episodes of stuttering in 82 cases. The most episodes of DIS were related to antipsychotic drugs (57%), mostly including clozapine, followed by central nervous system agents (11.6%) and anticonvulsant drugs (9.3%). The majority of the cases were male and between the ages of 31 and 40 years. Repetitions were the most frequent core manifestations of DIS. In 55.8% of the episodes of DIS, the offending drug was withdrawn to manage stuttering, which resulted in significant improvement or complete relief of stuttering in all cases. Based on the suggested pathophysiological mechanisms for developmental stuttering and neurotransmitters dysfunctions involved in speech dysfluency, it seems that the abnormalities of several neurotransmitters, especially dopamine and glutamate, in different circuits and areas of the brain, including cortico-basal ganglia-thalamocortical loop and white matter fiber tracts, may be engaged in the pathogenesis of DIS.

Keywords: Drug; Dysfluency; Dysphemia; Psychotropics; Speech; Stammering

Core Tip: Stuttering has two main types, developmental and acquired stuttering. Acquired stuttering is a manifestation of psychogenic or neurogenic disorders. Neurogenic stuttering is caused by brain injury, stroke, drugs, etc. Because most drugs inducing stuttering are used in the management of psychiatric and/or neurologic disorders, clinicians may merely attribute a new-onset stuttering to the worsening of the underlying disorder and neglect drugs as the causes of stuttering. Therefore, in this review, reports of drug-induced stuttering (DIS) are collected to provide information about epidemiological and clinical characteristics of DIS. Moreover, some pathophysiological changes are proposed as the underlying mechanisms of DIS.