Demystifying Pain During Microfocused Ultrasound: A Narrative Analysis of Facial Layer Sensitivity and Its Possible Correlation with Treatment Efficacy

Aesthetic Plast Surg. 2026 Mar 9. doi: 10.1007/s00266-026-05730-5. Online ahead of print.

ABSTRACT

BACKGROUND: Microfocused ultrasound (MFU) is a noninvasive technology for facial tightening that induces neocollagenesis through focal thermal coagulation. Although generally safe, pain during MFU remains a major limitation, with intensity varying by facial region and treatment depth. This variability may reflect intrinsic differences in neural density across facial layers.

OBJECTIVES: To analyze the anatomical and physiological basis of facial sensitivity and explore whether pain intensity during MFU could indicate accurate energy delivery to the subdermis or SMAS, which are histologically and functionally more innervated.

METHODS: A narrative review was conducted using PubMed, Scopus, and Web of Science databases (2009-2025). Keywords included facial innervation, cutaneous nociception, subcutaneous adipose tissue sensory innervation, SMAS anatomy, microfocused ultrasound, and pain perception. Eligible articles described facial anatomy, sensory physiology, or pain during MFU procedures.

RESULTS: Facial layers show distinct sensory profiles: The skin, SMAS, and periosteum are densely innervated, while subcutaneous fat contains few nociceptive fibers. Energy delivered to the subdermis or SMAS produces higher pain scores than treatment restricted to adipose tissue. Visualization-guided MFU (MFU-V) enhances targeting precision and is associated with increased discomfort, likely reflecting more accurate energy deposition.

CONCLUSION: Pain during MFU mirrors the neuroanatomical distribution of sensory fibers. The coincidence between highly innervated planes and optimal clinical outcomes suggests that moderate discomfort may represent a physiological marker of treatment accuracy rather than merely an adverse effect. Further clinical and histological studies are needed to validate pain as a surrogate indicator of effective energy delivery.

LEVEL OF EVIDENCE V: This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266.

PMID:41803309 | DOI:10.1007/s00266-026-05730-5