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Focused ultrasound7/11/2023 This study also utilized indirect targeting but modified the indirect target to treat at 2 mm above AC-PC. 6, 7 At 3 months, gait imbalance persisted in 26%, motor weakness in 7% and sensory deficits in 25%. side effects at 1 month included gait imbalance (46%), motor weakness (15%) and sensory deficits (33%). Similarly, in the most recent and largest retrospective study by Lak et al. At 3 months, numbness and paraesthesia decreased to 25% and objective ataxia to 3.6%, but weakness was unchanged. At 1 month, 29% of patients still had numbness and paraesthesia, 11% still had subjective ataxia and 4% still had weakness. 5 Thirty-eight percent of subjects developed numbness and paraesthesia, 20% developed objective ataxia and 4% developed weakness. 4 The pivotal multicenter, randomized clinical trial studying MRgHIFU for ET used indirect targeting. However, since MRgHIFU is an incisionless procedure, MER recordings cannot be obtained. During deep brain stimulation (DBS), microelectrode recordings (MERs) can be used to delineate the VIM. 2, 3 Although indirect targeting can identify a subcortical region in the vicinity of the VIM, a lack of well-defined boundaries limits accurate identification in high-resolution MRI. 1 Indirect targeting is a workhorse of functional neurosurgery, but limitations of indirect targeting include individual variations in anatomy and function, subjectivity in selecting anatomic landmarks and targets and the effects of underlying pathological derangement on intracranial structures. Standard imaging methods are unable to delineate the VIM, necessitating landmark-based (indirect) targeting approaches. The efficacy and safety of MRgHIFU depend upon precise targeting of subcortical targets. Magnetic resonance–guided high-intensity focused ultrasound (MRgHIFU) ablation of the ventral intermediate (VIM) nucleus of the thalamus is an incision-less, Food and Drug Administration (FDA) –approved procedure for essential tremor (ET) and Parkinson’s disease tremor. Initial experience using this approach suggests that it improves patient outcomes by reducing the incidence of adverse effects.įocused ultrasound, FUS, HIFU, essential tremor, diffusion tensor imaging Introduction Our method utilizes Food and Drug Administration-approved software and is easily implementable into existing workflows. ![]() Our method is novel because it targets both the decussating and non-decussating dentato-rubro-thalamic-tracts while avoiding the medial lemniscus and corticospinal tracts. We provide a technical overview and clinical benefits of our novel, easily implemented advanced tractography method: four-tract tractography. ![]() Targeting discrete white matter tracts with magnetic resonance–guided high-intensity focused ultrasound is an emerging precision medicine technique that has the promise to improve patient outcomes and reduce treatment times. There is considerable variability in fibre tracking algorithms and what fibres are tracked. Several recent reports have used diffusion tensor imaging to target the dentato-rubro-thalamic-tract. The target, the ventral intermediate nucleus of the thalamus, is not visualized on standard, anatomic MRI sequences. Magnetic resonance–guided high-intensity focused ultrasound thalamotomy is a Food and Drug Administration–approved treatment for essential tremor.
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