Is neurophysiology required for optimal deep brain stimulation targeting?

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Kim Burchiel

Acknowledging the lack of randomised data comparing the outcomes of “awake” versus “asleep” deep brain stimulation (DBS), Kim Burchiel (Oregon Health and Science University, Portland, USA) discusses the evolving evidence-base regarding the implantation of deep brain stimulation electrodes under general anesthesia, in turn highlighting an array of cognitive improvements found to be superior in the “asleep” DBS group. Comparing MRI and CT, he also proposes that “it is likely that one of these imaging systems will emerge as the dominant technology for image-guided DBS surgery”.

Implantation of deep brain stimulation (DBS) electrodes has traditionally been accomplished in awake patients, under local anesthesia, using microelectrode recording to physiologically verify target acquisition. Evidence is now mounting that image-guided implantation of DBS electrodes can be accomplished under general anesthesia in patients with Parkinson’s disease, and that post-operative outcomes under general anesthetic can be equivalent to those achieved using physiologic guidance, including motor (tested using the Unified Parkinson’s Disease Rating Scale; UPDRS II-III), levodopa equivalent daily dose, complications and adverse events, as well as target accuracy, inpatient length of stay and 30-day readmission rates. Compared to awake DBS, asleep DBS also results in less intracranial air, which is a potential source of brain shift and the malposition of electrodes. Results with asleep DBS for essential tremor indicate that there is comparable improvement in tremor when compared to “awake” DBS. Implant costs of awake and asleep DBS are comparable. Presently, no prospective randomised and controlled study has been completed comparing DBS under local anesthetic versus general, but a prospective trial is underway.

At Oregon Health and Science University, we have studied the issue of DBS implantation, and compared our latest results in awake patients with microelectrode recording, to a more recent cohort of patients in which asleep DBS was performed. The results showed that there was no significant difference observed in improvement of UPDRS III between awake and asleep patients. Interestingly, improvement in ON time without dyskinesia, quality of life scores for cognition and communication, and speech outcomes—notably category and phonemic fluency—were all superior in the asleep DBS group.1,2

There is an on-going discussion regarding what these findings portend for the future of DBS surgery. At the very least, image-guided DBS electrode implantation may be one option in the selection of appropriate surgical techniques for patients with Parkinson’s disease, essential tremor, and other disorders, who require DBS. Under this scenario, intraoperative imaging will likely be a requirement for image-guided DBS electrode placement.

Considerable work has already been accomplished using intraoperative MRI and CT guidance for DBS surgery. It is likely that one of these imaging systems will emerge as the dominant technology for image-guided DBS surgery. Where MRI has the advantages of no radiation and the potential for “live” updates of electrode position; cost, alongside accessibility and a compromised surgical environment, remain its shortcomings. CT has the advantage of being a less expensive and more accessible without the concerns of ferromagnetic instrumentation in the surgical field. Yet, it requires a radiation dose to the patient, which would only be increased by successive “live” updates, requiring repeated imaging. There may be other technologies that could reduce, or even obviate the need for intraoperative imaging—but these are yet to be developed.

The question at hand is whether awake DBS surgery, with microelectrode recording guidance, is the best way to conduct routine (non-research) implantation of DBS electrode for movement disorder therapy. Microelectrode recording is certainly the biggest challenge of awake surgery, in that it requires dedicated equipment, neurophysiologic expertise, an awake patient, and potentially more time in the operating room.

The main issue with microelectrode recording is that it also appears to have a linkage to intracerebral haemorrhage and stroke.3 Without a clear advantage of microelectrode recording mapping, this additional risk may not be justified. Further, 28,000 cases of DBS implantation procedures (2004–2013) from the CMS registry, and NSQIP have been examined, showing revision/removal rates of 15.2–34%, for the two registries, respectively. The authors of this study4 concluded that 48.5% of these replacements were due to improper targeting or lack of therapeutic effects. This is a concerning statistic given that virtually all of these procedures were performed on awake patients with microelectrode recording guidance. Thus, using the “gold-standard” approach, roughly 10–15% of all initial DBS implants in the USA appear to be mispositioned.

Without question, awake DBS with microelectrode recording is a valuable research approach to improve our understanding of Parkinson disease, essential tremor, and many other conditions. Although there is no prospective randomised trial data comparing the outcomes of awake and asleep DBS, the evidence is growing that routine awake DBS with microelectrode recording may be supplanted by asleep DBS utilising image-guidance, and intraoperative imaging.

With over 35 years of experience in the field, Kim Burchiel is the John Raaf professor and the Head of the Division of Functional Neurosurgery at Oregon Health and Science University. 

References

  1. Brodsky MA, Anderson A, Murchison C, Seier M, Wilhelm J, Vederman A, Burchiel KJ.  Clinical Outcomes of Asleep vs Awake Deep Brain Stimulation for Parkinson Disease. Neurology Nov 2017, 89 (19) 1944-1950; DOI:10.1212/WNL.0000000000004630.
  2. Aziz TZ, Hariz M. To Sleep or Not to Sleep During Deep Brain Stimulation Surgery for Parkinson Disease. Neurology Nov 2017, 89 (19) 1938-1939; DOI:10.1212/WNL.0000000000004635
  3. Zrinzo L, Foltynie T, Limousin P, Hariz MI: Reducing hemorrhagic complications in functional neurosurgery:  a large case series and systematic review.  J Neurosurg Sept 2011. [DOI: 10.3171/2011.8.JNS10147]
  4. Rolston JD, Englot DJ, Starr PA Larson PS. An unexpectedly high rate of revisions and removals in deep brain stimulation surgery: Analysis of multiple databases. Parkinsonism Relat Disord 2016 Dec;33:72-77. doi: 10.1016/j.parkreldis.2016.09.014. Epub 2016 Sep 12.

 

 


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