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ULTRASOUND ARTICLES
Echotexture and Correlated Histologic Analysis of Peripheral Nerves Important in Regional Anesthesia
  1. Sang-Hoon Lee, MD, PhD*,
  2. Sang-Heon Lee, MD, PhD†,
  3. Vincent W. S. Chan, MD‡,
  4. Jung-Ok Lee, PhD§ and
  5. Hyoung-Ihl Kim, MD, PhD§∥
  1. From the *Madi Pain Management Center, Jeonju, South Korea;
  2. †Department of Rehabilitation, College of Medicine, Korea University, Seoul, South Korea;
  3. ‡Department of Anesthesia, Toronto Western Hospital, University of Toronto, Ontario, Canada;
  4. §Department of Neurosurgery, Presbyterian Medical Center, Jeonju, South Korea;
  5. ∥Institute of Medical System Engineering, Gwangju Institute of Science and Technology, Gwangju, South Korea.
  1. Address correspondence to: Hyoung-Ihl Kim, MD, PhD, Institute of Medical System Engineering and School of Mechatronics, Gwangju Institute of Science & Technology, 261 Cheomdan-gwagiro, Gwangju 500-712, South Korea (e-mail: hyoungihl{at}gist.ac.kr).

Abstract

Background and Objectives: Peripheral nerves in different body locations display different echotextures on ultrasound imaging, and knowledge of peripheral nerve echotexture is helpful for locating target nerves. However, the degree of echogenicity is often difficult to characterize. We aimed to define objectively the degree of echogenicity of peripheral nerves using grayscale measurements and compare nerve echotexture with matched histologic samples.

Methods: Ultrasound images of peripheral nerves in 12 body locations were obtained in 20 healthy subjects using linear 8- to 12-MHz and curved 3- to 5-MHZ transducers. Corresponding nerve segments from 2 cadavers were imaged in vitro before they were sectioned for histologic examination. Nerve echogenicity was assessed by an objective grayscale (G) and a subjective echogenicity index (SEI) determined by experienced evaluators. The results of G and SEI in selected peripheral nerves were compared and correlated with histologic morphometry.

Results: There is a close correlation between SEI and G (P < 0.05). Mixed echogenicity was seen in 30% of the peripheral nerves; 25.4% were predominantly hypoechogenic, and 44.5% hyperechogenic. Nerves in the neck and upper arm are more frequently hypoechoic, whereas those in the leg are more frequently hyperechoic. Histologically, differences in echogenicity are dependent on fascicle diameter and on nerve fascicular pattern, that is, differing ratios of fascicle number to total nerve area.

Conclusions: This study suggests that grayscales can be used to objectively determine echogenicity and shows that grayscale measurements match well with subjective visual grading. Histologic analysis showed that both ratio of total fascicular area to whole nerve area and fascicular pattern are important determinants of echogenicity.

https://doi.org/10.1097/AAP.0b013e318217a7a0

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    Footnotes

    • Drs. Sang-Hoon Lee and Snag-Heon Lee are equal contributors.

    • The research was supported by a grant of the Institute of Medical System Engineering from Gwangju Institute of Science and Technology and a grant of the Korea Healthcare technology R&D Project (A091220), Ministry for Health, Welfare & Family Affairs, Republic of Korea.