Implications of botulinum toxin injection of the brow^∗

John Singer Sargent (1856-1925), Lady Agnew of Lochnaw, 1892. Observer's gaze is drawn to the lady's eyes, where her expression is framed and punctuated by a raised brow. Sir Charles Bell (1774-1842, anatomist, surgeon, and physiologist, best known for defining different functions for ventral and dorsal spinal roots, as well as for characterizing the facial nerve palsy bearing his name) regarded the corrugator muscle as “the most remarkable muscle of the human face. It knits the eyebrows with an energetic effort, which unaccountably, but irresistibly, conveys the idea of mind.”¹ Image reprinted courtesy of the National Gallery of Scotland.