Clinical improvement associated with targeted interruption of the cerebellothalamic tract following MR-guided focused ultrasound for essential tremor

Abstract

OBJECTIVE The objective of this study was to evaluate the utility of diffusion tensor imaging (DTI) tractography-based targeting of the dentatorubrothalamic tract (DRT) for magnetic resonance-guided focused ultrasound (MRgFUS) thalamotomy in patients with essential tremor (ET) and correlate postprocedural tract disruption with clinical outcomes. METHODS Four patients received preprocedural and immediate postprocedural DTI in addition to traditional anatomical MRI sequences for MRgFUS thalamotomy. Optimal ablation sites were selected based on the patient-specific location of the DRT as demonstrated by DTI (direct targeting) and correlated with traditional atlas-based measurements for thalamic ventral intermediate nucleus (Vim) lesioning (indirect targeting). Fiber tracts were displayed three-dimensionally during the procedure and used in conjunction with clinical signs of tremor control for fine correction of the ablation site. Immediately following the conclusion of the procedure, the MRgFUS head frame was removed and patients were placed in a 32-channel MRI head coil for follow-up DTI and anatomical MRI sequences. RESULTS All patients had excellent postoperative tremor control and successful pre- and postprocedural DTI fiber tracking of the corticospinal tract, medial lemniscus, and DRT. Immediate postprocedure DTI failed to track the DRT ipsilateral to the lesion site with a preserved contralateral DRT, coincident with substantial resolution of contralateral tremor. CONCLUSIONS DTI can reliably identify the optimal ablation target and demonstrates tract disruption on immediate postprocedural imaging. A clinical improvement of ET was observed immediately following the procedure, correlating with DRT disruption and suggesting that interruption of the DRT is a consequence of clinically successful MRgFUS thalamotomy. These findings may have utility for both MRgFUS procedure planning in surgically naive patients and retreatment of patients who have previously undergone unsuccessful thalamic Vim lesioning.

Neurological adverse event profile of magnetic resonance imaging–guided focused ultrasound thalamotomy for essential tremor

“…Targeting was performed using conventional stereotactic localization in the majority of MRgFUS patients. Imaging methods such as MRI diffusion tensor imaging tractography are under investigation to improve targeting for both FUS and DBS . Analyses of postprocedure MRI changes are also under study to improve outcome of sonication‐based ablation …”

The dentato-rubro-thalamic tract as the potential common deep brain stimulation target for tremor of various origin: an observational case series

“…There are some questions open. Why does a unilateral disruption of the DRT under conditions of a therapeutic intervention [11] alleviate tremor without detrimental side effects while sometimes a spontaneous lesion leaves a patient with catastrophic functional outcome [36]? One reason might be a shift of DRT physiological function to the side contralateral to the tremor.…”

“…[9]. Recently, the use of DTI-assisted targeting of the DRT for focused ultrasound lesioning was also described [11]. Beyond clinical effects, the claim that the DRT might be the actual common tremor-reducing structure for several indications has not been proven so far [23].…”

The Utility of Diffusion Tensor Imaging in Neuromodulation: Moving Beyond Conventional Magnetic Resonance Imaging

“…This suggests that personalized reconstruction of relevant tracts pretreatment is important for accurate DRT targeting at the individual level. In addition to targeting guidance and assessment of clinical outcome, posttreatment tractography of the DRT in follow‐up imaging has also been used as an indicator of treatment accuracy and efficacy .…”