Abstract
Background: Deep brain stimulation (DBS) is a neurosurgical intervention with demonstrated effectiveness for treatment resistant depression (TRD), but longitudinal studies on the stability of cognitive parameters following treatment are limited. The objectives of this study are to (i) identify baseline cognitive predictors of treatment response to subcallosal cingulate gyrus (SCG) DBS for unipolar TRD and (ii) compare neurocognitive performance prior to and 12 months after DBS implantation.Methods: Twenty unipolar TRD patients received SCG DBS for 12 months. A standardized neuropsychological battery was used to assess a range of neurocognitive abilities at baseline and after 12 months. Severity of depression was evaluated using the 17 item Hamilton Rating Scale for Depression.Results: Finger Tap-Dominant Hand Test and total number of errors made on the Wisconsin Card Sorting Test predicted classification of patients as treatment responders or non-responders, and were independent of improvement in mood. Change in verbal fluency was the only neuropsychological test that correlated with change in mood from baseline to the follow up period. None of the neuropsychological measures displayed deterioration in cognitive functioning from baseline to repeat testing at 12 months.Limitations: This was an open label study with a small sample size which limits predictive analysis. Practice effects of the neuropsychological testing could explain the improvement from baseline to follow up on some tasks. Replication using a larger sample of subjects who received neuropsychological testing before and at least 12 months after DBS surgery is required.Conclusion: These preliminary results (i) suggest that psychomotor speed may be a useful baseline predictor of response to SCG DBS treatment and (ii) support previous suggestions that SCG DBS has no deleterious effects on cognition.
Highlights
Treatment resistant depression (TRD) occurs in 30% of depressed patients attending hospital clinics (Rush et al, 2006) and has a prevalence of 22% in Canadian community samples (Rizvi et al, 2014)
The first deep brain stimulation (DBS) study in TRD to modulate subcallosal cingulate gyrus (SCG) over-activity was published in Mayberg et al (2005), and subsequent open-label trials have demonstrated that it is safe and effective in small open-label trials for treatment of TRD (McNeely et al, 2008; Holtzheimer et al, 2012; Merkl et al, 2013; Bogod et al, 2014)
Patients were classified as responders or non-responders after 12 months of chronic SCG DBS
Summary
Treatment resistant depression (TRD) occurs in 30% of depressed patients attending hospital clinics (Rush et al, 2006) and has a prevalence of 22% in Canadian community samples (Rizvi et al, 2014). Despite advances in drug development to treat major depressive disorder (MDD), there is no evidence that newer drugs have higher efficacy compared to first generation tricyclic antidepressants (Baghai et al, 2011). Functional neuroimaging research has provided evidence for abnormal neuronal circuits in MDD (Mayberg et al, 1999) which has contributed to the emerging interest in deep brain stimulation (DBS) and other targeted neurostimulation techniques to provide alternative treatment options for TRD. Deep brain stimulation (DBS) is a neurosurgical intervention with demonstrated effectiveness for treatment resistant depression (TRD), but longitudinal studies on the stability of cognitive parameters following treatment are limited. The objectives of this study are to (i) identify baseline cognitive predictors of treatment response to subcallosal cingulate gyrus (SCG) DBS for unipolar TRD and (ii) compare neurocognitive performance prior to and 12 months after DBS implantation
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