Results from a systematic review reveal that evidence for the use of deep brain stimulation (DBS) of various targets to promote recovery in patients with disorders of consciousness is based on a “small population of heterogeneous patients”. Ali Rezaei Haddad and colleagues from the University of Oxford, UK, report that in the eight studies analysed, time from injury to stimulation was “significantly variable and problematic”, while evidence supporting the use of DBS in minimally conscious patients following traumatic brain injury is lacking.
Recently published in Neuromodulation: Technology at the Neural Interface, the review was carried out using an array of electronic bibliographic databases to identify the relevant literature. “We included all studies describing applications of DBS on patients in minimally conscious state following traumatic brain injury,” write Haddad and colleagues.
Of the eight studies that were identified, the experience of DBS in 10 patients aged 15–58 was analysed. Acknowledging the variability, Haddad et al write: “The time from injury to simulation ranged from three to 252 months, with the duration of follow-up post-DBS ranging from 10 to 120 months.” While seven patients improved their post-surgical outcome score measures, a descriptive favourable outcome was reported in one patient. A further two patients were reported not to have shown any improvements following the intervention.
Providing an explanation for the variable time until stimulation, the authors highlighted that spontaneous recovery can occur within the first year of injury. However, Haddad and colleagues allude to the fact that spontaneous recovery presents as a “considerable issue” when examining the use of DBS in disorders of consciousness. “It has been reported that over four-fifths of patients who are in a minimally conscious state up to six months’ post-injury achieve spontaneous recovery by ten months. Furthermore, the recovery rates of traumatic brain injury patients are significantly higher when compared to other aetiologies,” write the authors, later acknowledging that while interpreting the results from DBS studies, “it is crucial to take into account the natural progression of this condition, especially at one-year post injury.”
In light of the findings, Haddad et al write: “This review suggests that future studies should attempt to adopt a patient-specific selection criterion rather than condition specific due to inaccuracies associated with the clinical diagnosis and different behavioural profiles of patients in minimally conscious state.” In addition, they put forward that patients should be randomised into stimulation and non-stimulation groups, and subsequently followed up for two to four years.
“Although some patients showed promising results in validated outcome measures, we conclude that the evidence supporting the use of DBS in minimally conscious state patients following traumatic brain injury is not sufficient as there is a lack of well-designed trials due to the challenges associated with this condition,” surmise Haddad and the team. Furthermore, they allude to the fact that despite the decreasing mortality rate associated with traumatic brain injury, the number of patients enduring long-term consequences of this injury, such as poor functional survival outcomes—including disordered consciousness—is on the rise. And, according to the authors, advances in neurosurgery and cute critical care only aids the acceleration of this figure.
Thus, referring to traumatic brain injury as a “silent epidemic” on a global scale, Haddad and colleagues maintain the importance of the need for interventions to reduce its incidence alongside improving the associated mortalities.