Deep brain stimulation is a therapy that hinges on three factors: accurate diagnosis and patient selection, electrodes placed with high surgical precision and appropriate application of stimulation settings. The DBS team is composed of several highly trained medical professionals that work together to make the best decision for the patient. This post focuses on the most obvious differences between awake versus asleep surgery. There are other factors that impact precision including brain imaging (CT is least precise), type of guidance system, patient factors, variation in patient anatomy, shift in brain target during surgery, and neurosurgeon experience, skill and training.
To date, there are no comparative studies to assess whether asleep DBS surgery is as effective as the the gold standard commonly known as awake surgery.
The debate about whether asleep DBS surgery is as good as or better than awake DBS surgery is speculation and a matter of opinion. Due to the lack of evidence that asleep surgery is as safe and effective as awake surgery, the patient will have to use their best judgement whether to pursue an experimental brain surgical technique. Since there are is no comparative research in which to judge asleep surgery, this post will highlight what can be assimilated into a thoughtful discussion so that patients can formulate their own opinion and decide if the unknowns are justified.
From a medical perspective, how does awake surgery and asleep surgery differ?
- Experience: Awake surgery has been performed over 100,000 times over more than 3 decades with high success in at least 3 brain targets (subthalamic nucleus or STN, thalamus or VIM, globus pallidus or GPi). Asleep surgery has been used for over a decade when the patient cannot be awake when safety may be a concern. The actual number of patients implanted while asleep is unknown as is the number of surgeons or DBS centers offering asleep surgery. There is no research data for us to compare the benefit and risks of asleep surgery to awake surgery. FDA approval of DBS is based entirely on the success of highly experienced DBS teams that utilize data obtained from an awake patient to guide final placement of the electrodes. The person seeking DBS will need to decide if the convenience of asleep surgery outweighs the awake time to collect individualized data to guide lead placement accuracy.
- Team: Asleep surgery eliminates the need for additional medical experts (neurologists, neurophysiologists) to provide data to support the judgement that the final placement of the electrodes is optimal. During awake DBS, neurology and/or neurophysiology experts provide their expertise with microelectrode recording analysis (MERA) and examination as well as test stimulation to customize the final placement of the electrode. The patient is also an integral part of the team to provide feedback during the physical examination while stimulation is tested to confirm whether symptoms respond to stimulation. If the neurology or neurophysiology experts are not part of the DBS team, interpreting data collected during awake surgery may be challenging. During asleep surgery, these experts and the patient response are eliminated, there is no MERA and no test stimulation to confirm stimulation will work and not cause intolerable side effects. During asleep surgery, the final position of the electrode is determined by the quality and interpretation of brain imaging and opinion of the surgeon. The person seeking DBS surgery will have to decide if one person (the surgeon) is enough to place their confidence and hope for the best possible outcome. The outcome cannot be known until the stimulation is turned on. The neurology members of the surgical team care for the patient long-term and are best suited to give input into the final placement of the electrodes that may give the best outcome.
- Brain Targets and Physiology: DBS history and expert opinion should not be disregarded.
- STN: Experienced DBS experts have emphasized the importance of microelectrode recording analysis (MERA) for targeting the subthalamic nucleus(1). MERA requires the patient to be awake.
- GPi: MERA is necessary for targeting the globus pallidus to avoid causing cognitive damage(2).
- VIM: Good results have been reported using only test stimulation without MERA(3). This still requires the patient to be awake in order to apply test stimulation prior to completing the surgery.
- Each patient has unique brain physiology and anatomy. For instance, a person with mostly tremor or mostly stiffness may respond better to different subsections of the STN. The unique factors related to the person’s symptoms and brain anatomy are taken into account when conducting awake DBS. These unique factors cannot be tested and electrode placement cannot be customized during asleep surgery.
- Brain Imaging: Brain imaging is utilized for both awake and asleep DBS surgery. Pre-surgery scans are mandatory. High resolution MRI is most accurate while CT fused to MRI allows for increased error. Awake DBS does not depend solely on brain imaging but incorporates the findings of the patient examination, MERA data and symptom response to test stimulation. During asleep DBS, the placement of the electrodes is determined after interpretation of your brain anatomy seen on MRI and or CT and someone’s opinion about your ideal location that is only a few millimeters. Millimeters matter as being off just two millimeters can compromise benefit and cause disabling side effects when stimulation is turned on. Asleep DBS using our current technology is a best guess with hopes for at least a reasonable outcome.
- Anesthesia: Awake DBS does not require anesthesia. Many patients actually end up sleeping during at least half of the time required to perform an awake procedure. The only time patients must be alert during awake DBS is during the time required to perform testing (about 2 hours). The actual impact of anesthesia on the brain is unknown however, all patients are at risk of confusion and psychosis after exposure to anesthesia. Even short term agitation and confusion can increase blood pressure which is a direct risk for bleeding in the brain.
- Programming: Microelectrode data collected during DBS surgery is useful to the neurology team that adjusts stimulation settings. For instance, when stimulation side effects limit benefit, a review of the results from MERA and test stimulation during the surgery may be helpful. This data also serves to avoid a time delay in pursuing revision surgery if the first chosen target was marginal during surgery and fails during stimulation adjustment.
- Re-operation: If the electrodes are not programmable, the information obtained during awake surgery will help the DBS team decide if a different brain target is the next logical step. If the patient was asleep during DBS surgery, there is very little information to guide decisions if revision surgery is needed. Re-operation comes with at least the same risks as the first surgery.
- Cost: The cost of repeating a failed DBS surgery is shouldered by the healthcare system and the patient in the form of co-pays, deductibles as well as additional radiation exposure if head CT is used. Revision surgery is not free. The cost of the evaluation to proceed to revision surgery, the discarded hardware and the cost to remove the old wires is added cost to the patient. The emotional expense to the patient and family can be un-measurable if revision surgery cannot be done.
- FDA: the FDA currently only recognizes the implantation of DBS in awake patients (FDA states “DBS should not be used in patients who do poorly with test stimulation.”)
Author’s Perspective – Asleep DBS has not been proven as effective as awake DBS.
DBS is a proven intervention by teams that include neurology and neurosurgery experts working together before, during and after the surgical event. Using research outcomes as our guide, a certain level of success is expected and is well documented by such expert teams. Highly experienced teams are best prepared to study and judge whether asleep DBS should be offered routinely. The skills required to utilize alternative techniques is also a consideration. Experienced DBS teams are most likely to have the skills to analyze a major shift in neurosurgical technique. A team of one should be pursued with caution.
Brain surgery is a serious matter for our patients that pursue a life changing procedure. DBS may be a last hope to get better and have a better life. I hold this hope in high regard and I prefer the highest accuracy so my patients have the greatest opportunity for excellent results. Not every patient can or will undergo revision surgery if the first DBS fails. Having access to every possible expert opinion matters the most on the day DBS wires are implanted. I prefer my patients to take no extra chances, cut no corners and make no compromises when it comes to a surgery that can change your life for the better.
When a medical procedure such as asleep DBS is highly marketed with unproven claims, caution is a natural reaction by DBS experts until the technique is proven to be as effective and safe. When a surgeon works without a team of trained experts, success is generally based on patient satisfaction with the procedure and the absence of complications. However, true outcomes require the oversight of a working team that hold each other accountable for accurate reporting and to a high bar of excellence. We base our decisions to recommend medical procedures to our patients after critical study by experts and asleep DBS surgery should be held to the same level of inquiry.
Until expert DBS teams have validated asleep DBS surgery for routine use, caution is highly advised. Lastly, until we have the data to make the best informed discussion about asleep DBS for our patients, awake surgery will continue to be available by expert DBS teams that give patients the best possible results with customized and precise implantation of the electrodes.
1. Benazzouz et al. Movement Disorders 2002;17(suppl 3);S145-S149.
2. Green et al. Brain Cogn. 2000;42(3):379-398.
3. Krauss et al. Neurosurgery. 2001;48(3):535-541.