Deep brain stimulation for treatment-refractory obsessive-compulsive disorder: Opportunities and challenges

To the Editor

We thank Malhi et al. (2022) for their interest in our Viewpoint article and their support for broadening access to deep brain stimulation (DBS) for people with severe obsessive-compulsive disorder (OCD) who have not responded to conventional pharmacological and psychological therapies. We concur with the sentiments of their commentary and would like to expand upon opportunities and challenges in this field.

Mahli et al. remark upon ‘. . . an opportunity to understand, innovate and explore . . .’ that is realised through DBS and the intersection of cognitive neuroscience, neurosurgery, neuroimaging and psychiatry. We suggest that with the advent of contemporary DBS technology, we are now on the cusp of a fundamental understanding of how DBS operates to change brain activity: (1) the latest DBS systems are approved for postoperative magnetic resonance brain imaging (MRI), allowing us to detect longitudinal changes in local and network-wide brain activity that correlate with symptomatic recovery after surgery; and (2) permanent DBS electrodes can record local neural activity as well as stimulate, letting us measure electrophysiological changes in brain tissue. This will undoubtedly yield further insights into brain networks that underpin dissociable effects on symptom dimensions (e.g. mood, cognitive inflexibility) as well as ‘common’ networks that associate with clinical response despite variability in stimulation site. Furthermore, through modelling how perturbations in focal brain activity are translated to network-wide changes, we may be able to accelerate the way that stimulation is delivered. Instead of measuring the effect of stimulation in reduction of expressed symptoms (a slow process that takes many months), we will be able to design a stimulation paradigm that biases local and network-wise brain activity towards those states associated with OCD symptom remission.

Collaboration between Australian sites providing DBS for OCD is an opportunity to rigorously collect outcome and safety data. We have applied to the Medical Research Future Fund (MRFF) to establish a data registry capturing all previous and prospective Australian cases of DBS for OCD. Pooling of data allows (1) benchmarking of clinical quality / safety between centres, (2) comparison of outcomes based on the precise stimulation site within the brain and (3) optimisation of the surgical target and stimulation parameters for future cases, based on emerging results from the existing cohort. Our long-term goal is to translate knowledge about brain network connectivity in OCD into a harmonised method for implanting DBS electrodes involving direct targeting of white matter tracts mediating improvement (i.e. personalised stimulation based on individually defined connectivity). This is noted in recently published consensus recommendations for the care of people with OCD undertaking DBS in Australia (Acevedo et al., 2022).

The foremost challenges to the future of DBS for OCD remain legislative barriers and a lack of a federal funding system. In Australia’s most populous state (NSW), DBS cannot be accessed because of an erroneous association of this reversible and non-destructive therapy with ‘psychosurgery’. Elsewhere in Australia, the number of people able to access DBS for OCD each year is constrained by the idiosyncrasies of local funding and the sparse availability of research grants. There is already an established pathway for federal reimbursement of DBS in the Medicare Benefits Schedule (MBS) for movement disorders such as Parkinson’s disease. We believe there are now sufficient data to justify the addition of OCD to these MBS items, increasing the availability of this treatment for those with severe forms of this terrible illness. This concern is an international one: termed a ‘crisis of access’ in a recent article in Nature Medicine (Visser-Vandewalle et al., 2022) written by a group of neurosurgeons, neurologists and psychiatrists:

DBS for OCD is a procedure that fulfils scientific and clinical criteria as an effective and safe therapy for patients suffering from severe intractable OCD. Failures of the healthcare system imperil people with this mental health condition, who are unable to receive this potentially life-saving therapy.