Aggravated stuttering following subthalamic deep brain stimulation in Parkinson's disease - two cases

Stuttering is a speech disorder with disruption of verbal fluency characterized by involuntary repetitions or prolongations of sounds or syllables. The pathogenesis of stuttering is not well understood. The most common form of stuttering is developmental stuttering, which evolves in childhood. Neurogenic or acquired stuttering occurs after a definable brain damage, e.g. stroke, intracerebral hemorrhage, or head trauma [1]. Acquired stuttering has been observed after lesions in a variety of brain areas, including lesions in the striatum or thalamus. The occurrence of basal ganglia disorders, such as Parkinson's disease (PD), occasionally leads to a re-emergence of recovered developmental stuttering [2].PD is a movement disorder defined by the presence of the cardinal motor features bradykinesia, rigidity and tremor. Long-term medical management of PD is frequently complicated by treatment-associated motor complications in the form of fluctuating motor function and dyskinesias. High-frequency deep brain stimulation (DBS) of the subthalamic nucleus (STN) is an effective treatment in advanced PD, improving all cardinal motor symptoms and treatment-related motor complications [3].DBS of different parts of the basal ganglia and thalamus have become widely applied surgical procedures. Observations on surgical and target related side effects have provided novel insights into the function of these parts of the brain. STN-DBS is currently the most common surgical procedure for patients with PD suffering from intolerable motor complications despite optimal medical treatment. Here we report the re-occurrence and aggravation of stuttering following STN-DBS in two male patients treated for advanced PD. This supports previous studies indicating a role for the STN in the development of stuttering.This 65-year-old right-handed man was diagnosed with PD at the age of 40 years. The disease had initially started with resting tremor on the right side, with subsequent development of rigi