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Michael Pourfar, Chengke Tang, Tanya Lin, Vijay Dhawan, Michael G. Kaplitt, and David Eidelberg

, supplementary motor area, and parietal association regions. The activity of this metabolic network is highly stable in individual patients and increases with disease progression. 3 The degree of network modulation achieved with treatment has been found to correlate with clinical outcome. 2 , 4 , 15 Thus, this metabolic imaging measure has been suggested as an objective biomarker of therapeutic response. Although significant reductions in PDRP expression have been reported after STN stimulation and gene therapy, 2 , 4 , 15 it is not known whether there was a microlesion

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Stéphane Derrey, Romain Lefaucheur, Nathalie Chastan, Emmanuel Gérardin, Didier Hannequin, Marie Desbordes, and David Maltête

C hronic high-frequency stimulation of the STN is currently the most common therapeutic surgical procedure for the advanced form of PD in patients in whom medical management has failed. 2 Compared with ablative surgery, deep brain stimulation is usually thought to be less destructive and a more adaptable method. 12 Nevertheless, a collision/implantation or microlesion effect, which is presumed to reflect disruption of cells and/or fibers consecutive to tracks affecting STN during the electrophysiological recordings and the placement of the definitive

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Takashi Morishita, Kelly D. Foote, Samuel S. Wu, Charles E. Jacobson IV, Ramon L. Rodriguez, Ihtsham U. Haq, Mustafa S. Siddiqui, Irene A. Malaty, Christopher J. Hass, and Michael S. Okun

M icroelectrode recording and macrostimulation (test stimulation) have been widely used to aid in refining the accuracy of DBS. These procedures appear to contribute to “implantation or microlesion” effects. 13 A microlesion effect is a phenomenon that can be evident clinically as an improvement in motor symptoms following a surgical procedure. 11 , 12 Although application of MER is still not universal, 1 , 3 , 7 , 15 most groups who perform DBS believe that MER can aid in refining DBS lead placement, and can potentially improve long-term outcome

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Omar K. Bangash, Arosha S. Dissanayake, Shirley Knight, John Murray, Megan Thorburn, Nova Thani, Arul Bala, Rick Stell, and Christopher R. P. Lind

.8 ± 5.3 14.1 ± 5.5 ET participants  1 M 52 11 Bilat  2 F 79 4 Bilat  3 M 62 12 Bilat  4 M 60 22 Bilat  Total 3 M, 1 F 4 bilat  Mean ± SD 63.3 ± 9.8 12.3 ± 6.4 Study Design Our experimental study was designed to assess the acute effects of PSA DBS on saccadic eye movements. Patients had saccadometry assessment preoperatively and postoperatively under the following stimulation parameters: 1) stimulator-off, corresponding to the “microlesion” (ML) condition and 2) high-frequency stimulation (HFS) condition, with an amplitude up to 3 V at 130 Hz and pulse width set to 90

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Alexander G. Chartrain, Ahmed J. Awad, Jonathan J. Rasouli, Robert J. Rothrock, and Brian H. Kopell

A 59-year-old woman with a 30-year history of essential tremor refractory to medical therapy underwent staged deep brain stimulation of the ventralis intermedius nucleus of the thalamus (VIM). Left-sided lead placement was performed first. Once in the operating room, microelectrode recording (MER) was performed to confirm the appropriate trajectory and identify the VIM border with the ventralis caudalis nucleus. MER was repeated after repositioning 2 mm anteriorly to reduce the likelihood of stimulation-induced paresthesias. Physical examination prior to permanent lead placement demonstrated micro-lesion effect, suggesting optimal trajectory. After implantation of the permanent lead, physical examination showed excellent results.

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Paul S. Larson and Steven W. Cheung

T innitus percepts are auditory phantoms without physical correlates. The condition is common, affecting 10%–15% of the adult population. Recently, a locus of the basal ganglia, area LC, located at the junction of the head and body of the caudate nucleus, was identified as a neuromodulation target for suppressing tinnitus. 2 , 3 Modulation of tinnitus by DBS in area LC has been attributed to neuromodulation and microlesion effects. Depending on the specific combination of stimulation parameters, acute neuromodulation of area LC alters tinnitus

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Cole A. Giller, Hanli Liu, Prem Gurnani, Sundar Victor, Umar Yazdani, and Dwight C. German

(Leadpoint v3.02; Medtronics, Minneapolis, MN). Microlesions in the Brain. At certain depths within the brain, microlesions were made at the end of some single-unit recording experiments. A 7-µA direct current was passed for 1 to 1.5 minutes. Histological examination of the microlesion sites indicated a lesion size of approximately 100 to 200 µm in diameter. Histological Evaluation One day after the NIR measurements had been obtained, animals were deeply anesthetized (Nembutal 120 mg/kg administered intraperitoneally) and perfused intracardially with 100 ml of

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Rebecca J. St George, Patricia Carlson-Kuhta, Kim J. Burchiel, Penelope Hogarth, Nicholas Frank, and Fay B. Horak

significant change seen in the STN group is therefore unlikely to be due to the natural rate of disease progression. Another possibility is that the surgical procedure created a microlesion in an area that contributes to the scaling of postural responses. Most surgeons are aware that prior to the initiation of stimulation, surgical tracts may cause microlesioning effects in STN surgery. 10 Cardinal PD signs of tremor, rigidity, and bradykinesia often show improvements from microlesions 26 still present after 6 months. 27 Negative microlesion effects are not unheard of

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Abdullah Keleş, Mehmet Volkan Harput, and Uğur Türe

and fourth ventricle surgery whenever possible (Yaşargil, 1996). After cutting the arachnoid trabeculae, the arachnoid was reflected laterally and fixed to the dura with hemoclips. A second microlesion was noticed on the posterior midline surface of the medulla oblongata. This lesion was not seen on preoperative studies. Before tumor dissection, this video angiography gave us detailed information on feeding arteries intraoperatively. Tumor dissection started with coagulation of the feeding arteries one by one. All vessels related to the lesion except the main

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H. T. Ballantine Jr., Eugene Bell, and Jesus Manlapaz

arbitrarily designated as our standard lesion one that results from an exposure of the brain to focused ultrasound of 2.7 Mc./sec. frequency for 0.4 sec. at an intensity of 1700 w./cm. 2 ( Fig. 4 ). A threshold or microlesion is shown in Fig. 5 . Irradiation parameters were 0.25 sec. duration of exposure and 1700 w./cm. 2 intensity. Fig. 4. Appearance of standard lesion 72 hrs. following irradiation with focused ultrasound. Frequency was 2.7 MC./sec., intensity 1700 w./cm. 2 , and duration of sound 0.4 sec. Note laminar appearance of necrotized tissue. Each mark