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J Neurosurg. 2019 Apr 26:1-6. doi: 10.3171/2019.2.JNS183517. [Epub ahead of print]

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

Author information

1
Departments of1Neurosurgery and.
2
2Radiology, Stanford University School of Medicine, Stanford, California.
3
3Department of Neurological Surgery, University of Virginia Health System, Charlottesville, Virginia.
4
4University of Maryland School of Medicine, Baltimore, Maryland.
5
5Swedish Neuroscience Institute, Seattle, Washington.
6
6Tokyo Women's Medical University, Tokyo, Japan.
7
7Yonsei University College of Medicine, Seoul, Korea.
8
8Sunnybrook Health Sciences Center, Toronto, Ontario, Canada.
9
9The Ohio State University Medical Center, Columbus, Ohio.
10
10Washoukai Sadamoto Hospital, Matsuyama City, Japan.
11
11Kumamoto University Hospital, Obihiro City, Japan.
12
12Osaka University Hospital, Osaka, Japan.
13
13Brigham and Women's Hospital, Boston, Massachusetts.
14
14ResoFUS Alomar, Barcelona, Spain.
15
15Weill Cornell School of Medicine, New York, New York.
16
16Nara Medical University, Kashihara, Japan.
17
17St. Mary's Hospital, London, United Kingdom; and.
18
18InSightec, Ltd., Dallas, Texas.

Abstract

OBJECTIVESkull 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.METHODSIn 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.RESULTSOf 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.CONCLUSIONSMRgFUS 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.

KEYWORDS:

CRST = Clinical Rating Scale for Tremor; ET; ET = essential tremor; FUS = focused ultrasound; MRgFUS; MRgFUS = magnetic resonance–guided focused ultrasound; SDR; SDR = skull density ratio; functional neurosurgery; magnetic resonance-guided focused ultrasound; skull density ratio

PMID:
31026836
DOI:
10.3171/2019.2.JNS183517

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