Muscle Ultrasound and Sarcopenia in Older Individuals: A Clinical Perspective.

INTRODUCTION: A precise quantitative measurement of skeletal muscle mass is fundamental for diagnosing sarcopenia in older individuals. The current techniques of assessment, including dual-energy x-ray absorptiometry (DXA), bioimpedance analysis (BIA), and magnetic resonance imaging (MRI) are either difficult to perform in everyday clinical practice or biased by concurrent clinical confounders. B-mode muscle ultrasound can be helpful in assessing muscle mass and architecture, and thus possibly useful for diagnosing or screening sarcopenia.

METHODS: A literature search of published articles on muscle ultrasound and sarcopenia in older individuals as of July 31, 2016, was made on PubMed and Scopus. Manual search and cross-referencing from reviews and original articles was also performed.

RESULTS: Most of the existing studies were carried out on healthy well-fit subjects, with a low prevalence of sarcopenia. The main parameters that can be assessed through muscle ultrasound are muscle thickness, cross-sectional area, echo intensity, and, for pennate muscles, fascicle length and pennation angle. In older subjects, all these parameters show some degree of alteration compared to young adults, particularly in lower limb muscles with antigravitary function, such as the quadriceps femoris and gastrocnemius medialis. Each of these parameters may be theoretically useful for detecting the loss of muscle mass and functionality in geriatric patients. They are also poorly influenced by the presence of acute and chronic diseases and fluid balance, unlike DXA and BIA, but a high degree of standardization in ultrasound protocols is necessary. Frontier applications of ultrasound in the assessment of sarcopenia may include contrast-enhanced and diaphragm ultrasound.

CONCLUSIONS: The current literature does not allow to make conclusive recommendations about the use of muscle ultrasound in geriatric practice. However, this technique is very promising, and further studies should validate its applications in the context of sarcopenia assessment.