Outcome and follow-up
Before surgery, both patients had MADRS scores of 44 and 49 points and
HAM-A scores of 40 points, corresponding to severe depressive and
anxiety symptoms (Table 2).
Patient 1 received DBS in the BNST for the initial three months and
experienced markedly reduced symptoms of depression and anxiety compared
to pre-surgery (reductions: MADRS 77%, HAM-A 65%, Table 2). After
switching to DBS in the MFB area, Patient 1 experienced an immediate
worsening of symptoms. He continued to report severe anxiety and mild
confusion and was offered to break the study protocol. However, the
patient continued and by the end of the three-month stimulation, the
depression and anxiety symptoms were only slightly reduced compared to
pre-surgery levels.
After completion of the randomization phase, DBS was resumed in BNST and
turned off in the MFB area. A week later the patient reported anxiety
relief. Over the next six months of BNST-DBS, the patient reported a
marked reduction in anxiety and therefore continued to receive BNST
stimulation during the four-year follow-up. Due to remaining depressive
symptoms, mainly apathy, DBS in the MFB area was reactivated, but the
patient did not experience any positive effect on depression during the
following months. When the current strength was increased, he
experienced fatigue and MFB-DBS was again inactivated. In year four,
MFB-DBS was reactivated at a low current level (0.5 volts), with the
intention to gradually increase the current to avoid triggering
additional side effects. Four years after surgery, stable improvements
were observed, especially regarding anxiety symptoms, but also
depression although the patient still reported feelings of apathy
(reductions: MADRS 48%, HAM-A 70%, Table 2).
Patient 2 received DBS in the MFB area for three months, and minor
reductions in depression and anxiety symptoms were recorded compared to
pre-surgery (reductions: MADRS 10%, HAM-A 25%, Table 2). After
switching to BNST-DBS, depressive symptoms were markedly reduced
(reductions: MADRS 51%, HAM-A 13%). In the open-label phase, BNST-DBS
was delivered and there was a gradual reduction of depression symptoms
fulfilling the criteria of remission and for anxiety symptoms five years
after surgery (reductions MADRS 55%, HAM-A 65%, Table 2). Attempts of
combined stimulation in both targets (BNST and MFB area) were performed,
but without any clear beneficial effects, and isolated BNST-DBS was used
for chronic stimulation.