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. 2019 Aug;60(8):768-773.
doi: 10.3349/ymj.2019.60.8.768.

Skull Factors Affecting Outcomes of Magnetic Resonance-Guided Focused Ultrasound for Patients with Essential Tremor

Kyung Won Chang  1 , Yong Sook Park  2 , Jin Woo Chang  3
Affiliations

Skull Factors Affecting Outcomes of Magnetic Resonance-Guided Focused Ultrasound for Patients with Essential Tremor

Kyung Won Chang et al. Yonsei Med J. 2019 Aug.

Abstract

Purpose: Magnetic resonance-guided focused ultrasound (MRgFUS) thalamotomy has become a standard treatment for medically intractable essential tremor (ET). Skull density ratio (SDR) and skull volume in patients with ET are currently considered useful indicators of the successful application of MRgFUS. We compared the clinical outcomes of MRgFUS thalamotomy with SDR above 0.4 and 0.45. We also described patterns of SDR and skull volume in Korean patients with ET who were eligible to be screened for MRgFUS.

Materials and methods: In screening 318 ET patients, we evaluated patterns of skull density and skull volume according to age and sex. Fifty patients with ET were treated with MRgFUS. We investigated the effects of SDR and skull volume on treatment parameters and the outcomes of ET.

Results: The mean SDR of the 318 ET patients was 0.45±0.11, and that for skull volume was 315.74±40.95 cm³. The male patients had a higher SDR than female patients (p=0.047). Skull volume significantly decreased with aging. SDR and skull volume exhibited a linear negative relationship. Among therapeutic parameters, maximal temperature was positively related to SDR, while sonication number was not related to either SDR or skull volume. Tremor outcome was also not related to SDR or skull volume.

Conclusion: SDR varied widely from 0.11 to 0.73, and men had a higher SDR. Therapeutic parameters and clinical outcomes were not affected by SDR or skull volume.

Keywords: Essential tremor; MRgFUS; magnetic resonance-guided focused ultrasound; skull density ratio; skull volume.

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Conflict of interest statement

The authors have no potential conflicts of interest to disclose.

Figures

Fig. 1
Fig. 1. Relationship for skull density ratio (SDR) in all screening patients with essential tremor. (A) Linear regression line between age and SDR (p>0.05). (B) Comparison of mean differences in SDR between male and female groups. Male patients show significantly higher SDR (p<0.05).
Fig. 2
Fig. 2. Relationship for skull volume in all screening patients with essential tremor (n=318). (A) Linear regression line between skull volume and age (p<0.001). (B) Comparison of mean differences in skull volume in the male and female patients. No difference is present.
Fig. 3
Fig. 3. The relationship between skull density ratio (SDR) and skull volume. The SDR and skull volume exhibited a negative linear relationship. (A) Skull volume=360.977−101.509×SDR for correlation of SDR and skull volume in SDR≥0.4. (B) Skull volume=370.702−119.365×SDR (p=0.001) for SDR≥0.45. (C) Skull volume=359.811−99.975×SDR (p=0.031). They all showed a significant relationship.
See this image and copyright information in PMC

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