Deep brain stimulation in movement and psychiatric disorders

Deep brain stimulation (DBS) is the most focal and invasive of the electromagnetic brain stimulation therapies. A subcutaneous pulse generator provides continuous stimulation of circumscribed brain tissue via a multicontact microelectrode that terminates within its target. The result is an adjustable, reversible, and specific therapy. Despite limited understanding of its mechanisms of action, DBS efficacy has been established in several movement disorders, and promising reports have emerged for Tourette syndrome, obsessive-compulsive disorder, and major depression. Deep brain stimulation may prove to be a reasonable option for severely ill and treatment-resistant patients who otherwise have limited therapeutic options and a poor prognosis.

Rostral cingulate gyrus: A putative target for deep brain stimulation in treatment-refractory depression

Surgery for intractable affective illnesses has generated considerable controversy over the last century. Deep brain stimulation (DBS) has revolutionized neurosurgical practice, especially in the field of advanced Parkinson's disease and, more recently, in selected medical-refractory cases of obsessive-compulsive disorder. In this paper, we propose a discrete area of the rostral cingulate gyrus as a potential target for DBS in medical-resistant depressive patients. Brodmann's area 24a has proved to be a vital link in the integration of neural circuits underlying depression, both through proposed neurobiological models and accurate neuroimaging studies. The full reversibility and adjustability of DBS offer the best chance to treat the multidimensional and life-span profile of depression, so giving hope to a great number of desperate human beings.

Deep brain stimulation for refractory obsessive-compulsive disorder

BACKGROUND

Neurosurgery (anterior capsulotomy) has been beneficial to many patients with debilitating, refractory obsessive-compulsive disorder (OCD), but the irreversibility of the procedure is an important limitation to its use. Nondestructive, electrical stimulation (deep brain stimulation; DBS) has proven an effective alternative to ablative surgery for neurological indications, suggesting potential utility in place of capsulotomy for OCD.

METHODS

The effects of DBS for OCD were examined in four patients in a short-term, blinded, on-off design and long-term, open follow-up. The patients had incapacitating illness, refractory to standard treatments. Hardware developed for movement disorder treatment was surgically implanted, with leads placed bilaterally in the anterior limbs of their internal capsules. Patients received stimulation in a randomized "on-off" sequence of four 3-week blocks. Ongoing, open stimulation was continued in consenting patients after the controlled trial.

RESULTS

Patients tolerated DBS well. Dramatic benefits to mood, anxiety, and OCD symptoms were seen in one patient during blinded study and open, long-term follow-up. A second patient showed moderate benefit during open follow-up.

CONCLUSIONS

It appears that DBS has potential value for treating refractory psychiatric disorders, but additional development work is needed before the procedure is utilized outside of carefully controlled research protocols.

Mechanisms and the current state of deep brain stimulation in neuropsychiatry

Deep brain stimulation (DBS) is established as a therapy for movement disorders, and it is an investigational treatment in other neurologic conditions. DBS precisely targets neuroanatomical targets deep within the brain that are proposed to be centrally involved in the pathophysiology of some neuropsychiatric illnesses. DBS is nonablative, offering the advantages of reversibility and adjustability. This might permit therapeutic effectiveness to be enhanced or side effects to be minimized. Preclinical and clinical studies have shown effects of DBS locally, at the stimulation target, and at a distance, via actions on fibers of passage or across synapses. Although its mechanisms of action are not fully elucidated, several effects have been proposed to underlie the therapeutic effects of DBS in movement disorders, and potentially in other conditions as well. The mechanisms of action of DBS are the focus of active investigation in a number of clinical and preclinical laboratories. As in severe movement disorders, DBS may offer a degree of hope for patients with intractable neuropsychiatric illness. It is already clear that research intended to realize this potential will require a very considerable commitment of resources, energy, and time across disciplines including psychiatry, neurosurgery neurology, neuropsychology, bioengineering, and bioethics. These investigations should proceed cautiously.

Neurosurgery for intractable obsessive-compulsive disorder and depression: critical issues

Intractable OCD and depression cause tremendous suffering in those affected and in their families. The impaired ability to function of those affected imposes a heavy burden on society as a whole. Existing data suggest that lesion procedures offer benefit to a large proportion (ranging from about 35%-70%) of patients with intractable OCD and depression. The literature also suggests that although serious long-term adverse events have occurred, these are relatively infrequent overall. Methodologic limitations of the earlier reports on any of these procedures were described previously in this article. The major academic centers conducting this work have since been obtaining systematic prospective data using modern assessment tools. Nevertheless, even with improved methodologies, more recent studies confront some remaining issues that have been difficult to overcome fully. First, the number of patients who have received any one procedure has been relatively small, constraining statistical power. This limits the ability of researchers to enhance patient selection based on clinical characteristics. This is important, because patients with intractable OCD and depression referred for neurosurgery have high rates of comorbid Axis I diagnoses, personality disorders, and functional impairments, which may have value in predicting response. Other features, such as age of onset, chronicity, and symptom subtypes, may be likewise useful. Another key factor in response may be postoperative management, which has varied most over time but also across patients enrolled in trials. As noted previously, randomized controlled trials of neurosurgical treatment for intractable psychiatric illness have not been reported, although one has been proposed for gamma knife capsulotomy in intractable OCD [23]. The development of deep brain stimulation has also made sham-controlled studies possible and also allows within-patient designs to be considered. Bearing these problems in mind, the literature does provide important guidance on a number of key points, including approaches to referral, patient selection, and the need for long-term prospective follow-up and postoperative management. Nevertheless, important gaps in knowledge remain in all these areas. Research is expected to narrow these gaps in a number of ways, including patient selection, optimizing the procedures themselves, and understanding the mechanisms of therapeutic action. Neuroimaging studies will play a key role in achieving these aims (see the article by Rauch in this issue). So will cross-species translational research on the anatomy and physiology of the pathways implicated in the pathophysiology and response to treatment in these disorders. Future research in psychiatric neurosurgery must proceed cautiously. A recent editorial statement of the OCD-DBS Collaborative Group [26] recommends a minimum set of standards for any multidisciplinary teams contemplating work in this domain. The rationale for those standards is found throughout this issue and is especially developed in the article by Fins. The need for safe and effective therapeutic options for people suffering with these severe illnesses is just as clear. The experience over the last several decades provides grounds for careful optimism that refined lesion procedures or reversible deep brain stimulation may relieve suffering and improve the lives of people with these devastating disorders.

From psychosurgery to neuromodulation and palliation: history's lessons for the ethical conduct and regulation of neuropsychiatric research

As we contemplate the emerging era of neuromodulation and imagine the utility of deep brain stimulation for disease entities in neurology and psychiatry, our enthusiasm is immediately tempered by history. Just a generation ago, other confident investigators were heralding invasive somatic therapies like prefrontal lobotomy to treat psychiatric illness. That era of psychosurgery ended with widespread condemnation, congressional calls for a ban, and avow that history should never repeat itself. Now, just 30 years later, neurologists, neurosurgeons, and psychiatrists are implanting deep brain stimulators for the treatment of Parkinson's disease and contemplating their use for severe psychiatric illnesses, such as obsessive-compulsive disorder and the modulation of consciousness in traumatic brain injury.