Background: A relevant proportion of patients with panic disorder (PD) does not improve even though they receive state of the art treatment for anxiety disorders such as cognitive-behavioural therapy (CBT). At the same time, it is known, that from a neurobiological point of view, PD patients are often characterised by prefrontal hypoactivation. Intermittent Theta Burst Stimulation (iTBS) is a non-invasive type of neurostimulation which can modulate cortical activity and thus has the potential to normalise prefrontal hypoactivity found in PD. We therefore aimed at investigating the effects of iTBS as an innovative add-on to CBT in the treatment for PD.
Methods: In this double-blind, bicentric study, 44 PD patients, randomised to sham or verum stimulation, received 15 sessions of iTBS over the left prefrontal cortex (PFC) in addition to 9 weeks of group CBT. Cortical activity during a cognitive as well as an emotional (Emotional Stroop) paradigm was assessed both at baseline and post-iTBS treatment using functional near-infrared spectroscopy (fNIRS) and compared to healthy controls.
Results: In this manuscript we only report the results of the emotional paradigm; for the results of the cognitive paradigm please refer to Deppermann et al. (2014). During the Emotional Stroop test, PD patients showed significantly reduced activation to panic-related compared to neutral stimuli for the left PFC at baseline. Bilateral prefrontal activation for panic-related stimuli significantly increased after verum iTBS only. Clinical ratings significantly improved during CBT and remained stable at follow-up. However, no clinical differences between the verum- and sham-stimulated group were identified, except for a more stable reduction of agoraphobic avoidance during follow-up in the verum iTBS group.
Limitations: Limitations include insufficient blinding, the missing control for possible state-dependent iTBS effects, and the timing of iTBS application during CBT.
Conclusion: Prefrontal hypoactivity in PD patients was normalised by add-on iTBS. Clinical improvement of anxiety symptoms was not affected by iTBS.
Keywords: ANOVA, analysis of variance; CAQ, Cardiac Anxiety Questionnaire; CBSI, correlation-based signal improvement; CBT, cognitive-behavioural therapy; Cognitive-behavioural therapy; ER, error rate; Emotion regulation; Functional near-infrared spectroscopy; HAM-A, Hamilton Anxiety Rating Scale; HHb, deoxyhemoglobin; Intermittent Theta Burst Stimulation; LOCF, last observation carried forward; O2Hb, oxyhemoglobin; PAS, Panic and Agoraphobia Scale; PD, panic disorder; PFC, prefrontal cortex; Panic disorder; RM-ANOVA, repeated-measures analysis of variance; ROI, region of interest; RT, reaction time; fNIRS, functional near-infrared spectroscopy; iTBS, intermittent Theta Burst Stimulation; rTMS, repetitive Transcranial Magnetic Stimulation.