Microelectrode Recording in DBS Found Not to Affect Motor Outcomes

Greater reduction in medications seen after surgery with microelectrode recording

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by Steve Bryson, PhD |

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The change in motor symptoms after deep brain stimulation (DBS) in people with Parkinson’s disease did not differ regardless of whether microelectrode recording was used during their surgery to guide electrode placement, a pooled analysis of published studies suggest.

However, the analysis found that a reduction in the use of Parkinson’s medications was greater after DBS with microelectrode recording.

Because of a lack of studies, a well-designed trial is needed to directly compare DBS with and without microelectrode recording, the researchers said.

The analysis was published in the Journal of Parkinson’s Disease in the study “The Role of Microelectrode Recording in Deep Brain Stimulation Surgery for Parkinson’s Disease: A Systematic Review and Meta-Analysis.”

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How is microelectrode recording used in deep brain stimulation surgery?

DBS is a surgical treatment for Parkinson’s that involves implanting a device in the brain to stimulate one of two adjacent areas — the globus pallidus interna and subthalamic nucleus (STN) — with electrical impulses.

Traditionally, DBS is performed when the patient is awake and under local anesthesia, allowing for intraoperative microelectrode recording (MER), in which electrodes are inserted into each side of the brain to determine the location of the permanent DBS electrode accurately. MER also allows the testing of stimulation during the surgery to assess responses and to screen for side effects.

Recent advances in MRI methods have made it possible to directly visualize electrode placement reliably. The potential advantage of this approach is that MER and operative testing are no longer needed, allowing the procedure to be conducted under general anesthesia, thereby improving patient comfort and reducing operative time and costs.

Although surgical methods with and without MER have been used in routine clinical practice, there is a lack of comparative studies.

To compare outcomes with or without MER, a team of researchers based at the Radboud University Medical Center in the Netherlands conducted a systematic review and a pooled analysis of the DBS literature.

“This is the first meta-analysis on the use of MER in STN-DBS-surgery for [Parkinson’s disease],” the team wrote.

Database searches yielded 30 studies which included 34 patient groups. Among them, 29 groups involved MER from 26 studies and five without MER from four studies.

The primary outcome investigated was the mean difference between the pre-operative motor symptoms without medication (off state), and post-operative symptoms with DBS turned on without medication, six to 24 months (two years) after surgery. Motor function was assessed by the Unified Parkinson’s disease rating scale part 3.

The pooled analysis revealed there was no significant difference in change in mean motor scores between the MER and non-MER groups (1.64 vs. 1.33).

The secondary outcome measure was a reduction in levodopa equivalent daily dose (LEDD) — the combined total of Parkinson’s medications.

LEDD was reported in 21 studies with 24 patient groups with MER and in three studies with four groups without MER. Although there was no difference in the pre-operative LEDD between the two groups, the team found a significant difference after the procedure. The mean difference in LEDD after DBS was 1.14 for the MER group versus 0.65 for the non-MER group.

The researchers noted that the largest non-MER study showed a small LEDD change, which could have been related to differences in stimulation protocols and medication reduction. As a result, “the effect of the relatively small change in LEDD in this single study made the difference in LEDD between the MER and non-MER group more significant.”

There was insufficient data to compare the quality of life between the two groups because only two non-MER studies reported this outcome.

No reliable analysis could be performed on complications, as studies did not report them consistently. There is no consensus on how surgery-related adverse events, such as bleeding (hemorrhages), were defined. Some studies described only hemorrhages with symptoms, others reported all hemorrhages, while several did not report any adverse events.

Most included studies were uncontrolled (without placebo or sham treatment) observational studies without random treatment assignments.

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The main weaknesses noted were a lack of detail to determine whether the position of the leads was verified by imaging and whether motor function was performed in a blinded fashion. Some studies had a high number of discontinuations with no reason provided.

Further analysis showed significant publication bias in the MER studies but not in the non-MER group. Publication bias occurs when outcomes influence the decision to publish. Publishing only the studies that show significant results biases findings in favor of positive results.

“This meta-analysis shows that there is no difference in clinical outcome between a surgical technique with and without MER,” the researchers wrote. “The role of MER in today’s DBS-surgery should be further investigated by properly designed prospective comparative trials, with a back-to-back comparison to an MRI-guided approach.”

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