Abstract

Objectives The microlesion effect is refers to the improvement of clinical symptoms after deep brain stimulation (DBS) lead placement and is suggested to indicate optimal lead placement. This phenomenon is well known for movement disorders, such as essential tremors and Parkinson disease, but very few studies have reported its implications in neuropsychiatric disorders. Our aim was to evaluate the magnitude of the microlesion effect in Tourette syndrome (TS) and the relationship between the microlesion effect and the anatomical location of implanted DBS leads.

Methods This study included 6 consecutive patients who underwent DBS for severe TS. All patients were male and their mean age was 28.5 ± 10.5 years. All patients were videotaped at baseline and on postoperative day (POD) 7, and motor and phonic tic frequencies were recorded. We also analyzed the precision of lead placement in normalized brain space and evaluated the normative connectome associated with precise electrode positions for improvement of tics.

Results The microlesion effect was observed as an improvement in tic symptoms in all patients. The median motor tic frequency was 20.2 tics/min (range, 9.7–60) at baseline and decreased to 3.2 tics/min (1.2–11.3) on POD 1 (z = −2.20, p = 0.028) and 5.7 tics/min (range, 1.9–16.6) on POD 7 (z = −2.20, p = 0.028). The median phonic tic frequency was 10.5 tics/min (range, 2.0−58.7) at baseline and decreased to 0.7 tics/min (range, 0−14.4) on POD 1 (z = −1.78, p = 0.075) and 2.25 tics/min (range, 1.3−13.7) on POD 7 (z = −1.57, p = 0.116). Image analyses revealed that the precise position of the electrode was directed toward the anteromedial centromedian nucleus. Normative connectome analysis demonstrated connections between improvement-related areas and wide areas of the prefrontal cortex.

Conclusion This study shows that the microlesion effect may appear as an immediate improvement following DBS lead placement even in patients with TS. Our results support the existence of a “sweet spot” for tic suppression in patients with severe TS, and clinicians should pay attention to this phenomenon in the postoperative evaluation of the lead position.

Competing Interest Statement

The authors have declared no competing interest.

Funding Statement

This study was partially supported by the Japan Society for the Promotion of Science (JSPS) Grant-in-Aid for Scientific Research (C) (Grant number: 18K08956), the Central Research Institute of Fukuoka University (Grant number: 201045), Takeda Science Foundation, and JSPS KAKENHI Grants (Grant numbers: JP16H06396 and JP16H06396).

Author Declarations

I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained.

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The details of the IRB/oversight body that provided approval or exemption for the research described are given below:

The study protocol was approved by the review board of our institute, Fukuoka University Medical Ethics Review Board (approval numbers: U02-02-001 and U22-02-012). Informed consent was obtained from all participants. The study was conducted according to the principles of the Declaration of Helsinki.

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Data Availability

All data produced in the present study are available upon reasonable request to the authors.

AbbreviationsANTsAdvanced Normalization Tools;CMcentromedian;CTcomputed tomography;DBSdeep brain stimulation;IPGimplantable pulse generator;MRImagnetic resonance imaging;TSTourette syndrome;VTAvolume of tissue activated;YGTSSYale Global Tic Severity Scale