Diagnostic Testing

The total hyperhidrotic surface area varies with each Frey syndrome patient (Fig. 6.1). For this reason, it is crucial to accurately map the affected area prior to proceeding with long-term treatment. Minor’s iodine starch test, first published in 1927, has remained the traditional method for the evaluation for gustatory sweating [12]. After thoroughly cleaning and drying the area in question, the skin is painted with a layer of 2% iodine solution and allowed to dry. A starch powder is then applied evenly over the site. The patient then chews a piece of gum for several minutes. If Frey syndrome is present, the patient will begin to sweat with the moistened starch reacting with the iodine to produce a dark blue discoloration on the skin surface (Fig. 6.2). The active fraction of the starch is amylose, a polymer

Fig. 6.1 Drawing of positive discoloration with consistent extension (striped area) and variable extension (stippled area) from Linder et al. [8]

Fig. 6.2 Minor’s starch iodide test on a patient with symptomatic gustatory sweating from Linder et al. [8] of the sugar a-D-glucose, which reacts the small molecules of iodine causing the blue color change [13]. This technique allows the surgeon to determine the precise borders of the affected area in preparation for preventive therapy.