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.
