Frailty and outcomes after unilateral MRI-guided focused ultrasound thalamotomy for tremor

Frailty is recognized as an important predictor of neurointerventional outcomes. MRI-guided focused ultrasound (MRgFUS) thalamotomy is a treatment option for patients with refractory essential tremor (ET) and tremor-dominant Parkinson's disease (TdPD). The aim of this study was to evaluate whether frailer MRgFUS thalamotomy patients had worse tremor outcomes or more complications.

The authors performed a cohort analysis of patients treated with MRgFUS between 2020 and 2023. Inclusion criteria were unilateral MRgFUS thalamotomy for ET or TdPD with available follow-up data (minimum 3-month follow-up). Frailty was assessed using the 11-item modified frailty index (mFI-11), which includes 11 medical comorbidities. Tremor outcomes were assessed using the Clinical Rating Scale for Tremor Part B. Complications assessed included disturbances of sensation, speech and swallowing, balance and gait, and strength.

In total, 169 eligible patients were identified, including 135 (79.9%) ET and 34 (20.1%) TdPD patients. Frailty did not result in significant differences in tremor outcomes in the combined (p = 0.833), ET (p = 0.902), or TdPD (p = 0.501) cohort, or in any adverse events at the last follow-up (all p > 0.05). The combined mean follow-up was 10.3 ± 5.8 months (range 3-24 months), with cohort-specific mean follow-ups of 10.8 ± 6.0 months for ET and 8.6 ± 4.6 months for TdPD. Between the ET and TdPD cohorts, no significant differences existed in age, sex, handedness, side treated, skull density ratio, number of sonications, peak and average temperatures, energy delivered, BMI, or American Society of Anesthesiologists classification. For medical comorbidities, only hypertension was significantly different (65.9% ET, 47.1% TdPD; p = 0.043). The ET patients were significantly frailer overall, with 20.7% ET and 35.3% TdPD patients considered robust (mFI-11 score of 0), 14.8% ET and 32.4% TdPD patients prefrail (mFI-11 score of 1), 25.9% ET and 8.8% TdPD patients frail (mFI-11 score of 2), and 38.5% ET and 23.5% TdPD patients severely frail (mFI-11 score ≥ 3) (p = 0.007).

Increasing frailty is not associated with worse outcomes, suggesting that MRgFUS may be appropriate even for frailer patients. ET patients are frailer than TdPD patients selected for MRgFUS.