Dermatologic Use of Botulinum Toxin Workup

Updated: Feb 07, 2019
  • Author: Zoltan Trizna, MD, PhD; Chief Editor: Dirk M Elston, MD  more...
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Diagnostic Procedures

Electromyography (EMG) is useful in exactly identifying the muscles underlying the wrinkles, especially the smaller muscles. EMG is also a good teaching tool. To perform the procedure, the active EMG electrode is inserted into the muscle and slowly advanced until a signal of maximum intensity is detected. This signal is generated by the contraction of the target muscle. The botulinum toxin is injected into the identified area. EMG is time consuming and adds to the expense of the procedure. Therefore, it is not frequently used in the general dermatologic practice. Several portable devices are available.

The starch-iodine test visually demonstrates the extent of hyperhidrosis and indicates the amount of sweating. This test is performed by exposing the hyperhidrotic area to paper impregnated with iodine or by layering a starch-iodine mixture onto the skin. The paper method may be better on the palms and soles, whereas layering the mixture is easier in the axillae. This test is contraindicated in patients with hypersensitivity to iodine. The presence of sweat results in a blue-black pigment reaction after about 10 minutes. By photocopying the paper or photographing the area, permanent documentation is achieved.

Sweating can be quantitatively measured by placing bibulous paper on the affected area. After a period of time, the increase in the weight of the paper is documented. Repeated measurements should be obtained under the same conditions of ambient temperature and elapsed time.