Answer:
Sensory innervation to the superior portion of the breast is supplied by the supraclavicular nerves formed from the third and fourth branches of the cervical plexus. The medial breast skin is supplied by the anterior cutaneous divisions of the second through seventh intercostal nerves. The dominant innervation to the nipple appears to derive from the lateral cutaneous branch of the fourth intercostal nerve, whereas lateral cutaneous branches of other intercostal nerves travel subcutaneously to the areola and the skin of the breast to and beyond the midclavicular line. Independent confirmation of the importance of the lateral cutaneous branch of the fourth intercostal nerve has led to greater acceptance of techniques that include its course in the vascular pedicle to the nipple. Sensation is preserved equally by inferior and superior pedicle techniques if the pedicles have a large base. Reduced sensitivity occurs in about 4%, and absent sensitivity occurs in about 1% of cases who undergo Lejour reduction. In another study, 4% lost sensibility in the group in which < 550 gram were removed (central or inferior pedicle) and 15% lost sensibility when > 550 gram were removed.