MR Guided Focused Ultrasound using VIM and VOP/A Dual-lesions for the Treatment of Tremor Dominant Parkinson’s Disease: Outcomes in Six Treated Cases.

Introduction: VIM is the preferred target in MRgFUS for TdPD. However, some TdPD patients have persistent tremor after VIM thalamotomy. A separate tremor network involving the basal ganglia with outflow through the ventralis oralis anterior and posterior (VOP/A) may be responsible. We present six TdPD cases with dual VIM and VOP/A MRgFUS thalamotomies.

Methods: Six patients with TdPD underwent VIM MRgFUS thalamotomy and had suboptimal or no intraprocedural improvement in resting and/or action tremors, and underwent concurrent VOP/A thalamotomy during the same procedure. Demographic and treatment information were collected. Tremor improvement was recorded using the CRST. Side effects and complication information were recorded.

Results: Mean age was 71.5 years (SD=2.7), 5 were male (83.3%), 4 were right-sided treatments (66.7%), and 1 was a second side treatment (16.7%). Mean VIM lesion coordinates were X=13.9mm, Y=7.5mm, and Z=2.2mm. VOP/A was targeted by moving approximately 3-5mm anterior and 3mm medial to the initial VIM lesion. Mean VOP/A lesion coordinates were X=11.7mm, Y=11.3mm, and Z=2.3mm.

Intraprocedurally, after VIM thalamotomy, 5 patients had satisfactory control of postural/action tremor (83.3%) and none had satisfactory control of resting tremor (0%). After VOP/A thalamotomy, control of postural/action remained at 5 patients (83.3%), but those 5 patients gained satisfactory control of resting tremor (83.3%). Immediately after MRgFUS, 2 patients reported altered speech (33.3%) and 4 patients reported balance/gait complications (66.6%). These improved to 1 patient with altered speech (16.7%) and 2 patients with balance/gait complications (33.3%) at last follow up (mean 3.7 months, range 1 to 6 months). Updated follow-up data will be provided at the meeting.

Conclusion : TdPD patients with tremor refractory to VIM MRgFUS thalamotomy may benefit from a secondary lesion in VOP/A.