Neurogenic stuttering caused by supplementary motor area and premotor cortex dysfunction due to acute encephalopathy: A case report

Stuttering is a speech disorder characterized by disruptions in fluency and rhythm and is often accompanied by secondary motor symptoms such as tension in the face, neck, and fingers. Thus, motor control dysfunction is an important contributing factor. Fluent speech relies on precise internal timing, and improvements with external cues support the hypothesis of impaired internal motor timing. We present a case of neurogenic stuttering and limb motor incoordination resulting from bilateral supplementary motor area (SMA) and premotor cortex (PMC) dysfunctions. A 9-year-old right-handed boy with normal development developed acute encephalopathy at 1 year 3 months. Magnetic resonance imaging (MRI) and single-photon emission computed tomography revealed bilateral SMA and PMC involvement. Although the patient had no intellectual disabilities, expressive language was delayed relative to comprehension. Stuttering emerged after 4 years, with difficulty in speech initiation and secondary behaviors, such as facial tension, word substitutions, and excessive limb movements. At 9 years, standardized assessment revealed moderate stuttering severity (4/6). Fluent speech was observed while singing, playing games, or with external cues. Neurological findings included mild left-dominant incoordination and clumsy foot stepping, which improved when attention was on bilateral rhythmic hand movements. MRI at 9 years revealed no structural abnormalities. The findings were more consistent with neurogenic than developmental stuttering. This case demonstrates a compensatory mechanism through which external cues support impaired internal timing of speech and limb motor control. Patient improvement using external cues provides insight into the pathophysiology of stuttering and motor timing disorders associated with SMA and PMC dysfunction.