Impact of skull density ratio on efficacy and safety of magnetic resonance–guided focused ultrasound treatment of essential tremor

Marissa D’Souza, Kevin S. Chen, Jarrett Rosenberg, W. Jeffrey Elias, Howard M. Eisenberg, Ryder Gwinn, Takaomi Taira, Jin Woo Chang, Nir Lipsman, Vibhor Krishna, Keiji Igase, Kazumichi Yamada, Haruhiko Kishima, Rees Cosgrove, Jordi Rumià, Michael G. Kaplitt, Hidehiro Hirabayashi, Dipankar Nandi, Jaimie M. Henderson, Kim Butts PaulyMor Dayan, Casey H. Halpern, Pejman Ghanouni

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34 Citations (Scopus)


OBJECTIVE Skull density ratio (SDR) assesses the transparency of the skull to ultrasound. Magnetic resonance–guided focused ultrasound (MRgFUS) thalamotomy in essential tremor (ET) patients with a lower SDR may be less effective, and the risk for complications may be increased. To address these questions, the authors analyzed clinical outcomes of MRgFUS thalamotomy based on SDRs. METHODS In 189 patients, 3 outcomes were correlated with SDRs. Efficacy was based on improvement in Clinical Rating Scale for Tremor (CRST) scores 1 year after MRgFUS. Procedural efficiency was determined by the ease of achieving a peak voxel temperature of 54°C. Safety was based on the rate of the most severe procedure-related adverse event. SDRs were categorized at thresholds of 0.45 and 0.40, selected based on published criteria. RESULTS Of 189 patients, 53 (28%) had an SDR < 0.45 and 20 (11%) had an SDR < 0.40. There was no significant difference in improvement in CRST scores between those with an SDR ≥ 0.45 (58% ± 24%), 0.40 ≤ SDR < 0.45 (i.e., SDR ≥ 0.40 but < 0.45) (63% ± 27%), and SDR < 0.40 (49% ± 28%; p = 0.0744). Target temperature was achieved more often in those with an SDR ≥ 0.45 (p < 0.001). Rates of adverse events were lower in the groups with an SDR < 0.45 (p = 0.013), with no severe adverse events in these groups. CONCLUSIONS MRgFUS treatment of ET can be effectively and safely performed in patients with an SDR < 0.45 and an SDR < 0.40, although the procedure is more efficient when SDR ≥ 0.45.

Original languageEnglish
Pages (from-to)1392-1397
Number of pages6
JournalJournal of neurosurgery
Issue number5
Publication statusPublished - 2020 May

Bibliographical note

Funding Information:
InSightec provided research funding for clinical trials related to MRgFUS treatment of essential tremor. Drs. Ghanouni, Halpern, Henderson, Elias, Eisenberg, Gwinn, Taira, Chang, Lipsman, Krishna, Igase, Yamada, Kishima, Cosgrove, Rumià, Kaplitt, Hirabayashi, Eisenberg, and Nandi receive research funding from InSightec. Conduct of the study, data analysis and interpretation, and preparation and approval of the manuscript were done independently of InSightec. Initial design of the study was performed by Drs. Ghanouni, Halpern, and Dayan, who is an employee of InSightec. Data collection was performed by Dr. Dayan, who also reviewed the manuscript. Dr. Elias reports receiving support of non–study-related clinical or research efforts that he oversees from InSightec. Dr. Taira reports being a consultant for InSightec Japan. Dr. Lipsman reports having served as chair on the Expert Steering Committee of the Focused Ultrasound Foundation. Dr. Krishna reports receiving funding for a clinical trial from InSightec. Dr. Yamada reports receiving support for the study described from Hokuto Hospital. Dr. Cosgrove reports receiving research funding for clinical trials from InSightec. Dr. Halpern reports receiving speaking honoraria from Mazor Robotics and being a consultant for Medtronic. Dr. Ghanouni reports receiving support of non– study-related clinical or research efforts that he oversees from InSightec. Dr. Dayan is an employee of InSightec.

Publisher Copyright:
© AANS 2020, except where prohibited by US copyright law.

All Science Journal Classification (ASJC) codes

  • Surgery
  • Clinical Neurology


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