Neuronal effects of glabellar botulinum toxin injections using a valenced inhibition task in borderline personality disorder.

Previous studies have indicated that glabellar botulinum toxin (BTX) injections may lead to a sustained alleviation of depression. This may be accomplished by the disruption of a facial feedback loop, which potentially mitigates the experience of negative emotions. Accordingly, glabellar BTX injection can attenuate amygdala activity in response to emotional stimuli. A prototypic condition with an excess of negative emotionality and impulsivity accompanied by elevated amygdala reactivity to emotional stimuli is borderline personality disorder (BPD). In order to improve the understanding of how glabellar BTX may affect the processing of emotional stimuli and impulsivity, we conducted a functional magnetic resonance imaging (fMRI) study. Our hypotheses were (1) glabellar BTX leads to increased activation in prefrontal areas during inhibition performance and (2) BTX decreases amygdala activity during the processing of emotional stimuli in general. Using an emotional go-/no-go paradigm during fMRI, the interference of emotion processing and impulsivity in a sample of n = 45 women with BPD was assessed. Subjects were randomly assigned to BTX treatment or serial acupuncture (ACU) of the head. After 4 weeks, both treatments led to a reduction in the symptoms of BPD. However, BTX treatment was specifically associated with improved inhibition performance and increased activity in the motor cortex. In addition, the processing of negative emotional faces was accompanied by a reduction in right amygdala activity. This study provides the first evidence that glabellar BTX injections may modify central neurobiological and behavioural aspects of BPD. Since the control treatment produced similar clinical effects, these neurobiological findings may be specific to BTX and not a general correlate of symptomatic improvement.