scholarly journals Focused ultrasound thalamotomy location determines clinical benefits in patients with essential tremor

Brain ◽  
2018 ◽  
Vol 141 (12) ◽  
pp. 3405-3414 ◽  
Author(s):  
Alexandre Boutet ◽  
Manish Ranjan ◽  
Jidan Zhong ◽  
Jurgen Germann ◽  
David Xu ◽  
...  
Keyword(s):  
Adverse Effects ◽  
Essential Tremor ◽  
Diffusion Weighted Imaging ◽  
Focused Ultrasound ◽  
Medial Lemniscus ◽  
Intermediate Nucleus ◽  
Diffusion Weighted ◽  
Increased Risk ◽  
Clinical Benefits ◽  
Ventral Intermediate Nucleus

Abstract Magnetic resonance guided focused ultrasound (MRgFUS) thalamotomy is a novel and minimally invasive ablative treatment for essential tremor. The size and location of therapeutic lesions producing the optimal clinical benefits while minimizing adverse effects are not known. We examined these relationships in patients with essential tremor undergoing MRgFUS. We studied 66 patients with essential tremor who underwent MRgFUS between 2012 and 2017. We assessed the Clinical Rating Scale for Tremor (CRST) scores at 3 months after the procedure and tracked the adverse effects (sensory, motor, speech, gait, and dysmetria) 1 day (acute) and 3 months after the procedure. Clinical data associated with the postoperative Day 1 lesions were used to correlate the size and location of lesions with tremor benefit and acute adverse effects. Diffusion-weighted imaging was used to assess whether acute adverse effects were related to lesions encroaching on nearby major white matter tracts (medial lemniscus, pyramidal, and dentato-rubro-thalamic). The area of optimal tremor response at 3 months after the procedure was identified at the posterior portion of the ventral intermediate nucleus. Lesions extending beyond the posterior region of the ventral intermediate nucleus and lateral to the lateral thalamic border were associated with increased risk of acute adverse sensory and motor effects, respectively. Acute adverse effects on gait and dysmetria occurred with lesions inferolateral to the thalamus. Lesions inferolateral to the thalamus or medial to the ventral intermediate nucleus were also associated with acute adverse speech effects. Diffusion-weighted imaging revealed that lesions associated with adverse sensory and gait/dysmetria effects compromised the medial lemniscus and dentato-rubro-thalamic tracts, respectively. Lesions associated with adverse motor and speech effects encroached on the pyramidal tract. Lesions larger than 170 mm3 were associated with an increased risk of acute adverse effects. Tremor improvement and acute adverse effects of MRgFUS for essential tremor are highly dependent on the location and size of lesions. These novel findings could refine current MRgFUS treatment planning and targeting, thereby improving clinical outcomes in patients.

Tractography-based targeting of the ventral intermediate nucleus: accuracy and clinical utility in MRgFUS thalamotomy

2020 ◽  
Vol 133 (4) ◽  
pp. 1002-1009 ◽  
Author(s):  
Manish Ranjan ◽  
Gavin J. B. Elias ◽  
Alexandre Boutet ◽  
Jidan Zhong ◽  
Powell Chu ◽  
...  
Keyword(s):  
Adverse Effects ◽  
Clinical Utility ◽  
Focused Ultrasound ◽  
Patient Specific ◽  
Medial Lemniscus ◽  
Intermediate Nucleus ◽  
Increased Risk ◽  
Indirect Treatment ◽  
Ventral Intermediate Nucleus ◽  
Selection Of

OBJECTIVETractography-based targeting of the thalamic ventral intermediate nucleus (T-VIM) is a novel method conferring patient-specific selection of VIM coordinates for tremor surgery; however, its accuracy and clinical utility in magnetic resonance imaging–guided focused ultrasound (MRgFUS) thalamotomy compared to conventional indirect targeting has not been specifically addressed. This retrospective study sought to compare the treatment locations and potential adverse effect profiles of T-VIM with indirect targeting in a large cohort of MRgFUS thalamotomy patients.METHODST-VIM was performed using diffusion tractography outlining the pyramidal and medial lemniscus tracts in 43 MRgFUS thalamotomy patients. T-VIM coordinates were compared with the indirect treatment coordinates used in the procedure. Thalamotomy lesions were delineated on postoperative T1-weighted images and displaced (“translated”) by the anteroposterior and mediolateral difference between T-VIM and treatment coordinates. Both translated and actual lesions were normalized to standard space and subsequently overlaid with areas previously reported to be associated with an increased risk of motor and sensory adverse effects when lesioned during MRgFUS thalamotomy.RESULTST-VIM coordinates were 2.18 mm anterior and 1.82 mm medial to the “final” indirect treatment coordinates. Translated lesions lay more squarely within the boundaries of the VIM compared to nontranslated lesions and showed significantly less overlap with areas associated with sensory adverse effects. Translated lesions overlapped less with areas associated with motor adverse effects; however, this difference was not significant.CONCLUSIONST-VIM leads to the selection of more anterior and medial coordinates than the conventional indirect methods. Lesions moved toward these anteromedial coordinates avoid areas associated with an increased risk of motor and sensory adverse effects, suggesting that T-VIM may improve clinical outcomes.

Multimodal MRI for MRgFUS in essential tremor: post-treatment radiological markers of clinical outcome

2020 ◽  
Vol 91 (9) ◽  
pp. 921-927
Author(s):  
Anish N Kapadia ◽  
Gavin J B Elias ◽  
Alexandre Boutet ◽  
Jürgen Germann ◽  
Aditiya Pancholi ◽  
...  
Keyword(s):  
Adverse Effects ◽  
Clinical Outcome ◽  
Essential Tremor ◽  
Focused Ultrasound ◽  
Lesion Size ◽  
Post Treatment ◽  
Medial Lemniscus ◽  
Invasive Treatment ◽  
Tremor Suppression ◽  
Registration Number

BackgroundMRI-guided focused ultrasound (MRgFUS) thalamotomy is a promising non-invasive treatment option for medication-resistant essential tremor. However, it has been associated with variable efficacy and a relatively high incidence of adverse effects.ObjectivesTo assess the evolution of radiological findings after MRgFUS thalamotomy and to evaluate their significance for clinical outcomes.MethodsNinety-four patients who underwent MRgFUS between 2012 and 2017 were retrospectively evaluated. Lesion characteristics were assessed on routine MRI sequences, as well as with tractography. Relationships between imaging appearance, extent of white matter tract lesioning (59/94, on a 4-point scale) and clinical outcome were investigated. Recurrence was defined as >33% loss of tremor suppression at 3 months relative to day 7.ResultsAcute lesions demonstrated blood products, surrounding oedema and peripheral diffusion restriction. The extent of dentatorubrothalamic tract (DRTT) lesioning was significantly associated with clinical improvement at 1 year (t=4.32, p=0.001). Lesion size decreased over time (180.8±91.5 mm3 at day 1 vs 19.5±19.3 mm3 at 1-year post-treatment). Higher post-treatment oedema (t=3.59, p<0.001) was associated with larger lesions at 3 months. Patients with larger lesions at day 1 demonstrated reduced rates of tremor recurrence (t=2.67, p=0.019); however, lesions over 170 mm3 trended towards greater incidence of adverse effects (sensitivity=0.60, specificity=0.63). Lesion encroachment on the medial lemniscus (Sn=1.00, Sp=0.32) and pyramidal tract (Sn=1.00, Sp=0.12) were also associated with increased adverse effects incidence.ConclusionLesion size at day 1 predicts symptom recurrence, with fewer recurrences seen with larger lesions. Greater DRTT lesioning is associated with treatment efficacy. These findings may have implications for lesion targeting and extent.Trial registration numberNCT02252380.

scholarly journals Targeting of the dentato-rubro-thalamic tract for MR-guided focused ultrasound treatment of essential tremor

2019 ◽  
Vol 32 (6) ◽  
pp. 401-407 ◽  
Author(s):  
Timothy R Miller ◽  
Jiachen Zhuo ◽  
Howard M Eisenberg ◽  
Paul S Fishman ◽  
Elias R Melhem ◽  
...  
Keyword(s):  
Magnetic Resonance ◽  
Essential Tremor ◽  
Focused Ultrasound ◽  
Ultrasound Treatment ◽  
Diffusion Tractography ◽  
Intermediate Nucleus ◽  
Ultrasound Ablation ◽  
Ventral Intermediate Nucleus ◽  
Direct Targeting ◽  
Focused Ultrasound Ablation

Background Magnetic resonance-guided focused ultrasound ablation of the thalamic ventral intermediate nucleus is a safe and effective treatment for medically refractory essential tremor. However, indirect targeting of the ventral intermediate nucleus using stereotactic coordinates from normal neuroanatomy can be inefficient. We therefore evaluated the feasibility of supplementing this method with direct targeting of the dentato-rubro-thalamic tract. Methods We retrospectively identified four patients undergoing magnetic resonance-guided focused ultrasound ablation for essential tremor in which preoperative diffusion tractography imaging of the dentato-rubro-thalamic tract was fused with T2 weighted-imaging and utilized for intra-procedural targeting. The size and location of the dentato-rubro-thalamic tract and 24-hour lesion, as well as the center of the stereotactic coordinates, was evaluated. Finally, the amount of overlap between the dentato-rubro-thalamic tract and the lesion was calculated. Results The 24-hour lesion size was homogeneous in the cohort (mean 31.3 mm2, range 30–32 mm2), while there was substantial variation in the dentato-rubro-thalamic tract area (mean 14.3 mm2, range 3–24 mm2). The center of the stereotactic coordinates and dentato-rubro-thalamic tract diverged by more than 1 mm in mediolateral and anterposterior directions in all patients, while the dentato-rubro-thalamic tract and lesion centers were in close proximity (mean mediolateral separation 1 mm, range 0.1–2.2 mm; mean anteroposterior separation 0.75 mm, range 0.4–1.2 mm). There was greater than 50% coverage of the dentato-rubro-thalamic tract by the lesion in all patients (mean 82.9%, range 66.7–100%). All patients experienced durable tremor relief. Conclusion Direct targeting of the dentato-rubro-thalamic tract using diffusion tractography imaging fused to T2 weighted-imaging may be a useful strategy for focused ultrasound treatment of essential tremor. Further investigation of the technique is warranted.

Correlation between fractional anisotropy changes in the targeted ventral intermediate nucleus and clinical outcome after transcranial MR-guided focused ultrasound thalamotomy for essential tremor: results of a pilot study

2020 ◽  
Vol 132 (2) ◽  
pp. 568-573 ◽  
Author(s):  
Hiroki Hori ◽  
Toshio Yamaguchi ◽  
Yoshiyuki Konishi ◽  
Takaomi Taira ◽  
Yoshihiro Muragaki
Keyword(s):  
Clinical Outcome ◽  
Essential Tremor ◽  
Fractional Anisotropy ◽  
Focused Ultrasound ◽  
Rating Scale ◽  
Statistical Significance ◽  
Intermediate Nucleus ◽  
Ventral Intermediate Nucleus ◽  
Recurrence Group

OBJECTIVEThis study evaluated changes of fractional anisotropy (FA) in the ventral intermediate nucleus (VIM) of the thalamus after transcranial MR-guided focused ultrasound (TcMRgFUS) thalamotomy and their associations with clinical outcome.METHODSClinical and radiological data of 12 patients with medically refractory essential tremor (mean age 76.5 years) who underwent TcMRgFUS thalamotomy with VIM targeting were analyzed retrospectively. The Clinical Rating Scale for Tremor (CRST) score was calculated before and at 1 year after treatment. Measurements of the relative FA (rFA) values, defined as ratio of the FA value in the targeted VIM to the FA value in the contralateral VIM, were performed before thalamotomy, and 1 day and 1 year thereafter.RESULTSTcMRgFUS thalamotomy was well tolerated and no long-term complications were noted. At 1-year follow-up, 8 patients demonstrated relief of tremor (improvement group), whereas in 4 others persistent tremor was noted (recurrence group). In the entire cohort, mean rFA values in the targeted VIM before treatment, and at 1 day and 1 year after treatment, were 1.12 ± 0.15, 0.44 ± 0.13, and 0.82 ± 0.22, respectively (p < 0.001). rFA values were consistently higher in the recurrence group compared with the improvement group, and the difference reached statistical significance at 1 day (p < 0.05) and 1 year (p < 0.01) after treatment. There was a statistically significant (p < 0.01) positive correlation between rFA values in the targeted VIM at 1 day after thalamotomy and CRST score at 1 year after treatment. Receiver operating characteristic curve analysis revealed that the optimal cutoff value of rFA at 1 day after thalamotomy for prediction of symptomatic improvement at 1-year follow-up is 0.54.CONCLUSIONSTcMRgFUS thalamotomy results in significant decrease of rFA in the targeted VIM, at both 1 day and 1 year after treatment. Relative FA values at 1 day after treatment showed significant correlation with CRST score at 1-year follow-up. Therefore, FA may be considered a possible imaging biomarker for early prediction of clinical outcome after TcMRgFUS thalamotomy for essential tremor.

DBS targeting for essential tremor using intersectional dentato-rubro-thalamic tractography and direct proton density visualization of the VIM: technical note on 2 cases

2021 ◽  
pp. 1-9
Author(s):  
Melanie A. Morrison ◽  
Anthony T. Lee ◽  
Alastair J. Martin ◽  
Cameron Dietiker ◽  
Ethan G. Brown ◽  
...  
Keyword(s):  
Essential Tremor ◽  
Rating Scale ◽  
Technical Note ◽  
Electrode Placement ◽  
Proton Density ◽  
Clinical Benefits ◽  
Mri Sequences ◽  
Ventral Intermediate Nucleus ◽  
Deep Brain

OBJECTIVEDirect visualization of the ventral intermediate nucleus (VIM) of the thalamus on standard MRI sequences remains elusive. Therefore, deep brain stimulation (DBS) surgery for essential tremor (ET) indirectly targets the VIM using atlas-derived consensus coordinates and requires awake intraoperative testing to confirm clinical benefits. The objective of this study was to evaluate the utility of proton density (PD)–weighted MRI and tractography of the intersecting dentato-rubro-thalamic tract (DRTT) for direct “intersectional” targeting of the VIM in ET.METHODSDBS targets were selected by identifying the VIM on PD-weighted images relative to the DRTT in 2 patients with ET. Tremor reduction was confirmed with intraoperative clinical testing. Intended target coordinates based on the direct intersectional targeting technique were compared with consensus coordinates obtained with indirect targeting. Pre- and postoperative tremor scores were assessed using the Fahn-Tolosa-Marin tremor rating scale (TRS).RESULTSPlanned DBS coordinates based on direct versus indirect targeting of the VIM differed in both the anteroposterior (range 0 to 2.3) and lateral (range −0.7 to 1) directions. For 1 patient, indirect targeting—without PD-weighted visualization of the VIM and DRTT—would have likely resulted in suboptimal electrode placement within the VIM. At the 3-month follow-up, both patients demonstrated significant improvement in tremor symptoms subjectively and according to the TRS (case 1: 68%, case 2: 72%).CONCLUSIONSDirect intersectional targeting of the VIM using PD-weighted imaging and DRTT tractography is a feasible method for DBS placement in patients with ET. These advanced targeting techniques can supplement awake intraoperative testing or be used independently in asleep cases to improve surgical efficiency and confidence.

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