suggested by Rystedt et al.,8
the equivalent Onabotulinumtoxin A units utilized in our patient is still only around 35 units, which is significantly below the acceptable maximum 100 Onabotulinumtoxin A units recommended in the neck and still less than the upper limit of units used by many authors.Another possibility is that our technique of injecting into the muscle belly instead of using a “bleb” technique, as done by other specialists, may cause increased diffusion to deeper structures. However, we pinch the muscle as we inject it, thus lifting it away from deeper structures making this less likely as an explanation.Lastly, inadvertent intravascular injection and subsequent spread may be a mechanism that most likely accounts for the side effects in this patient. In prior studies of Rimabotulinumtoxin B for axillary hyperhidrosis9, 7 of 20 subjects (35%) experienced mild to moderate dry mouth lasting from 2 to 38 days. Furthermore, 5 of 20 subjects (25%) experienced dry eyes lasting 2 to 128 days. The distant nature of the side effects from the treatment sites may be suggestive of systemic diffusion rather than local diffusion.Although botulinum toxin-A is generally considered a safe off-label treatment for vertical platysma bands, one should still be aware of the possible side-effects even with low dose use, as supported by our case report of dysphagia with relatively conservative doses of Abobotulinumtoxin A.