Patient-Reported Outcomes After Focused Ultrasound Thalamotomy for Tremor-Predominant Parkinson’s Disease

Neurosurgery 93:884–891, 2023

Magnetic resonance–guided focused ultrasound (MRgFUS) has emerged as a precise, incisionless approach to cerebral lesioning and an alternative to neuromodulation in movement disorders. Despite rigorous clinical trials, long-term patient-centered outcome data after MRgFUS for tremor-predominant Parkinson’s Disease (TPPD) are relatively lacking.

OBJECTIVE: To report long-term data on patient satisfaction and quality of life after MRgFUS thalamotomy for TPPD.

METHODS: In a retrospective study of patients who underwent MRgFUS thalamotomy for TPPD at our institution between 2015 and 2022, a patient survey was administered to collect self-reported measures of tremor improvement, recurrence, Patients’ Global Impression of Change (PGIC), and side effects. Patient demographics, FUS parameters, and lesion characteristics were analyzed.

RESULTS: A total of 29 patients were included with a median follow-up of 16 months. Immediate tremor improvement was achieved in 96% of patients. Sustained improvement was achieved in 63% of patients at last follow-up. Complete tremor recurrence to baseline occurred for 17% of patients. Life quality improvement denoted by a PGIC of 1 to 2 was reported by 69% of patients. Long-term side effects were reported by 38% of patients and were mostly mild. Performing a secondary anteromedial lesion to target the ventralis oralis anterior/posterior nucleus was associated with higher rates of speech-related side effects (56% vs 12%), without significant improvement in tremor outcomes.

CONCLUSION: Patient satisfaction with FUS thalamotomy for tremor-predominant PD was very high, even at longer term. Extended lesioning to target the motor thalamus did not improve tremor control and may contribute to greater frequency of postoperative motor- and speech-related side effects.

Initial experience with magnetic resonance–guided focused ultrasound stereotactic surgery for central brain lesions in young adults

J Neurosurg 137:760–767, 2022

Magnetic resonance–guided focused ultrasound (MRgFUS) is an incisionless procedure capable of thermoablation through the focus of multiple acoustic beams. Although MRgFUS is currently approved for the treatment of tremor in adults, its safety and feasibility profile for intracranial lesions in the pediatric and young adult population remains unknown.

METHODS The long-term outcomes of a prospective single-center, single-arm trial of MRgFUS at Nicklaus Children’s Hospital in Miami, Florida, are presented. Patients 15–22 years of age with centrally located lesions were recruited, clinically consistent with WHO grade I tumors that require surgical intervention. This cohort consisted of 4 patients with hypothalamic hamartoma (HH), and 1 patient with tuberous sclerosis complex harboring a subependymal giant cell astrocytoma (SEGA).

RESULTS In each case, high-intensity FUS was used to target the intracranial lesion. Real-time MRI was used to monitor the thermoablations. Primary outcomes of interest were tolerability, feasibility, and safety of FUS. The radiographic ablation volume on intra- and postoperative MRI was also assessed. All 5 patients tolerated the procedure without any complications. Successful thermoablation was achieved in 4 of the 5 cases; the calcified SEGA was undertreated due to intratumor calcification, which prevented attainment of the target ablation temperature. The HHs underwent target tissue thermoablations that led to MR signal changes at the treatment site. For the patients harboring HHs, FUS thermoablations occurred without procedure-related complications and led to improvement in seizure control or hypothalamic hyperphagia. All 5 patients were discharged home on postoperative day 1 or 2, without any readmissions. There were no cases of hemorrhage, electrolyte derangement, endocrinopathy, or new neurological deficit in this cohort.

CONCLUSIONS This experience demonstrates that FUS thermoablation of centrally located brain lesions in adolescents and young adults can be performed safely and that it provides therapeutic benefit for associated symptoms. Clinical trial registration no.: NCT03028246


Prospective Tractography-Based Targeting for Improved Safety of Focused Ultrasound Thalamotomy

Neurosurgery 84:160–168, 2019

Focused ultrasound thalamotomy (FUS-T) was recently approved for the treatment of refractory essential tremor (ET). Despite its noninvasive approach, FUS-T reinitiated concerns about the adverse effects and long-term efficacy after lesioning.

OBJECTIVE: To prospectively assess the outcomes of FUS-T in 10 ET patients using tractography-based targeting of the ventral intermediate nucleus (VIM).

METHODS: VIM was identified at the intercommissural plane based on its neighboring tracts: the pyramidal tract and medial lemniscus. FUS-T was performed at the center of tractography-defined VIM. Tremor outcomes, at baseline and 3 mo, were assessed independently by the Tremor Research Group.We analyzed targeting coordinates, clinical outcomes, and adverse events. The FUS-T lesion location was analyzed in relation to unbiased thalamic parcellation using probabilisitic tractography. Quantitative diffusionweighted imaging changes were also studied in fiber tracts of interest.

RESULTS: The tractography coordinates were more anterior than the standard. Intraoperatively, therapeutic sonications at the tractography target improved tremor (>50% improvement) without motor or sensory side effects. Sustained improvement in tremor was observed at 3mo(tremor score: 18.3±6.9 vs 8.1±4.4, P=.001).Nomotorweakness and sensory deficits after FUS-T were observed during 6-mo follow-up. Ataxia was observed in 3 patients. FUS-T lesions overlapped with the VIM parcellated with probablisitic tractography. Significant microstructural changes were observed in the white matter connecting VIM with cerebellum and motor cortex.

CONCLUSION: This is the first report of prospective VIM targeting with tractography for FUS-T. These results suggest that tractography-guided targeting is safe and has satisfactory short-term clinical outcomes.

Minimally invasive treatment of intracerebral hemorrhage with magnetic resonance–guided focused ultrasound

Sonothrombolysis in ICH

J Neurosurg 118:1035–1045, 2013

Intracerebral hemorrhage (ICH) is a major cause of death and disability throughout the world. Surgical techniques are limited by their invasive nature and the associated disability caused during clot removal. Preliminary data have shown promise for the feasibility of transcranial MR-guided focused ultrasound (MRgFUS) sonothrombolysis in liquefying the clotted blood in ICH and thereby facilitating minimally invasive evacuation of the clot via a twist-drill craniostomy and aspiration tube.

Methods and Results. In an in vitro model, the following optimum transcranial sonothrombolysis parameters were determined: transducer center frequency 230 kHz, power 3950 W, pulse repetition rate 1 kHz, duty cycle 10%, and sonication duration 30 seconds. Safety studies were performed in swine (n = 20). In a swine model of ICH, MRgFUS sonothrombolysis of 4 ml ICH was performed. Magnetic resonance imaging and histological examination demonstrated complete lysis of the ICH without additional brain injury, blood-brain barrier breakdown, or thermal necrosis due to sonothrombolysis. A novel cadaveric model of ICH was developed with 40-ml clots implanted into fresh cadaveric brains (n = 10). Intracerebral hemorrhages were successfully liquefied (> 95%) with transcranial MRgFUS in a highly accurate fashion, permitting minimally invasive aspiration of the lysate under MRI guidance.

Conclusions. The feasibility of transcranial MRgFUS sonothrombolysis was demonstrated in in vitro and cadaveric models of ICH. Initial in vivo safety data in a swine model of ICH suggest the process to be safe. Minimally invasive treatment of ICH with MRgFUS warrants evaluation in the setting of a clinical trial.