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The Sensory Assessment After FTM Gender Affirming Mastectomy (SAFTY) Study
Siyou Song, BA, Laura Barnes, MD, Esther A. Kim, MD.
University of California San Francisco, San Francisco, CA, USA.

PURPOSE: The double-incision gender-affirming mastectomy with free-nipple graft (DM-FNG) is increasing in demand. One concern is sensation loss to the chest and nipple areolar complex (NAC); however, the extent of sensation loss is poorly understood. Therefore, this study aims to quantify the degree and timing of sensation return to the chest and NAC to improve counseling and expectations for patients.
METHODS: Participants are enrolled at consultations and post-DM-FNG follow-ups. Semmes-Weinstein Monofilaments, ranging from 1.65-6.50 mm, assessed light touch and pressure at standardized locations (Figure 1). Sizes up to 2.83, 3.61, and 4.31 represent normal sensation, diminished light touch, and diminished protective sensation, respectively. Test tubes filled with warm and cool water assessed temperature sensibility.
RESULTS: Sensory tests were performed on 16 preoperative and 29 postoperative patients. There were no significant differences in demographics and clinical characteristics (Table 1). 100% and 89.7% of preoperative and postoperative patients correctly identified warm and cool stimuli, respectively (p=0.18).
At different postoperative times, there is normal sensation in the upper chest (F1, G-H1, G-H2), but decreased sensation closer to the NAC (G3, H3, p=0.023-0.037) (Table 2). Patients less than a year postoperatively have significantly decreased sensation along the inframammary scar (A-C) (p=0.0006-0.003), mid-axillary line (D-D2) (p=0.014-0.048), and nipple (p=0.00037-0.002).
For breasts that had more than 500 g resected, there were significant sensation decreases along the inframammary scar (B, C) (p=0.004-0.031), mid-axillary line (D-D3) (p=0.00016-0.015), and below the inframammary scar (A1-C1) (p=0.014-0.04), whereas breasts with less than 500 g resected had normal sensation at those locations (Table 2).
48.3% had absent nipple sensation postoperatively (Table 3). Compared to preoperative breasts, postoperative breasts had significantly reduced nipple sensation at all times (p=0.00000037-0.018). For those who were able to sense any stimuli on their nipples, a thicker monofilament size was required (4.45-4.46, p=0.00037-0.002) (Table 2).
CONCLUSION: Postoperative sensation is normal except on the nipple, inframammary scar, and mid-axillary line. The inframammary scar is located along the dermatome of the 4th intercostal nerve that is routinely resected in DM-FNGs. Patients with large breasts have gravitational traction injury of their intercostal nerves with concomitant binding due to gender dysphoria have decreased sensation at baseline, which may explain why those with larger resected weights have less sensation postoperatively. Those who retained nipple sensibility had diminished protective sensation, increasing their risk for pressure injury. Protection against temperature injury was preserved. Understanding how sensation returns will better align patient expectations with outcomes.




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