Neurostimulation and the minimally conscious state

Deep brain stimulation for disorders of consciousness: Systematic review of cases and ethics

BACKGROUND

A treatment for patients suffering from prolonged severely altered consciousness is not available. The success of Deep Brain Stimulation (DBS) in diseases such as Parkinson's, dystonia and essential tremor provided a renewed impetus for its application in Disorders of Consciousness (DoC).

OBJECTIVE

To evaluate the rationale for DBS in patients with DoC, through systematic review of literature containing clinical data and ethical considerations.

METHODS

Articles from PubMed, Embase, Medline and Web of Science were systematically reviewed.

RESULTS

The outcomes of 78 individual patients reported in 19 articles from 1968 onwards were pooled and elements of ethical discussions were compared. There is no clear clinical evidence that DBS is a treatment for DoC that can restore both consciousness and the ability to communicate. In patients who benefitted, the outcome of DBS is often confounded by the time frame of spontaneous recovery from DoC. Difficult ethical considerations remain, such as the risk of increasing self-awareness of own limitations, without improving overall wellbeing, and the issues of proxy consent.

CONCLUSION

DBS is far from being evident as a possible future therapeutic avenue for patients with DoC. Double-blind studies are lacking, and many clinical and ethical issues have to be addressed. In the rare cases when DBS for patients with DoC is considered, this needs to be evaluated meticulously on a case by case basis, with comprehensive overall outcome measures including psychological and quality-of-life assessments, and with the guidance of an ethical and interdisciplinary panel, especially in relation to proxy consent.

Results of a prospective study (CATS) on the effects of thalamic stimulation in minimally conscious and vegetative state patients

OBJECTIVE Deep brain stimulation of the thalamus was introduced more than 40 years ago with the objective of improving the performance and attention of patients in a vegetative or minimally conscious state. Here, the authors report the results of the Cortical Activation by Thalamic Stimulation (CATS) study, a prospective multiinstitutional study on the effects of bilateral chronic stimulation of the anterior intralaminar thalamic nuclei and adjacent paralaminar regions in patients affected by a disorder of consciousness. METHODS The authors evaluated the clinical and radiological data of 29 patients in a vegetative state (unresponsive wakefulness syndrome) and 11 in a minimally conscious state that lasted for more than 6 months. Of these patients, 5 were selected for bilateral stereotactic implantation of deep brain stimulating electrodes into their thalamus. A definitive consensus for surgery was obtained for 3 of the selected patients. All 3 patients (2 in a vegetative state and 1 in a minimally conscious state) underwent implantation of bilateral thalamic electrodes and submitted to chronic stimulation for a minimum of 18 months and a maximum of 48 months. RESULTS In each case, there was an increase in desynchronization and the power spectrum of electroencephalograms, and improvement in the Coma Recovery Scale-Revised scores was found. Furthermore, the severity of limb spasticity and the number and severity of pathological movements were reduced. However, none of these patients returned to a fully conscious state. CONCLUSIONS Despite the limited number of patients studied, the authors confirmed that bilateral thalamic stimulation can improve the clinical status of patients affected by a disorder of consciousness, even though this stimulation did not induce persistent, clinically evident conscious behavior in the patients. Clinical trial registration no.: NCT01027572 ( ClinicalTrials.gov ).

Deep brain stimulation in persistent vegetative States: ethical issues governing decision making

The aim of the present paper was to investigate the fundamental ethical issues of Deep Brain Stimulation (DBS) on patients remaining in Persistent Vegetative State (PVS). First, the purpose of this analysis was to discuss the nature of this intervention in order to classify it such as an ordinary clinical practice, or otherwise as an extraordinary clinical practice or as experimental research. Second, ethical issues, criticisms, and methodological issues of this intervention, also in the future perspectives, are discussed, attempting to identify who could give informed consent for a patient in PVS.

[New indications for deep brain stimulation: ethical criteria for research and therapy]

The applications of deep brain stimulation (DBS) are rapidly increasing and now include a large variety of neurological and psychiatric diseases, such as depression, obsessive compulsive disorders, addiction, Alzheimer's disease, anorexia nervosa and rare movement disorders. These new applications confer a huge therapeutic potential in diseases for which often no treatment exists or which are refractory to existing therapies. This spread of applications, however, implies ethical problems in several domains: clinical use, research and presentation in the media and public. Thus, a systematic ethical analysis is needed to inform and guide this process. In this article we identify ethical problems involved in research and clinical use of novel DBS applications, suggest criteria and distinctions for structuring the ethical analysis, and articulate ethical demands for DBS research of novel applications.

An overview of intervention options for promoting adaptive behavior of persons with acquired brain injury and minimally conscious state

This paper presents an overview of the studies directed at helping post-coma persons with minimally conscious state improve their adaptive behavior. Twenty-one studies were identified for the 2000-2010 period (i.e., a period in which an intense debate has occurred about diagnostic, rehabilitative, prognostic, and ethical issues concerning people with severe acquired brain injury). Three of the 21 studies involved transcortical magnetic or deep brain stimulation. Six studies focused on the provision of multisensory stimulation or music therapy. The remaining 12 studies involved the use of response-related (contingent) stimulation and assistive technology. The outcomes of the studies, which were generally reported as positive, were discussed in terms of (a) the size (quantitative relevance) of the changes obtained, (b) the credibility/reliability of the changes, in light of the methodological conditions of the studies, and (c) the level of engagement and interaction involvement of the participants. Relevant issues for future research were also examined.

Deep brain stimulation in the management of disorders of consciousness: a review of physiology, previous reports, and ethical considerations

Patients suffering from disorders of consciousness constitute a population that exists largely outside of the daily practice patterns of neurosurgeons. Historically, treatment has focused on nursing and custodial issues with limited neurosurgical intervention. Recently, however, deep brain stimulation has been explored to restore cognitive and physical function to patients in minimally conscious states. In this article, the authors characterize the physiological mechanisms for the use of deep brain stimulation in persistently vegetative and minimally conscious patients, review published cases and associated ethical concerns, and discuss future directions of this technology.