Surgery is necessary for the permanent reduction of excessive focal axillary hyperhidrosis (FAH). Recently, minimally invasive strategies such as superficial liposuction, manual curettage, or liposuction curettage have been favored, and complete excision of the axillary skin is performed less frequently [1–6]. Although several techniques have been reported to be effective and beneficial to the patients’ quality of life, nonresponders with recurrent sweating remain a problem [6]. Efficacy seems to rise with the aggressiveness of the procedure, as sharp cannulas have been shown to reduce sweat rates more effectively than blunt instruments [7, 8]. However, the recurrence rate varies widely in the literature, ranging from 2% to 20% [2, 9]. The exact reason for inadequate surgery still remains unclear. Some authors believe that the minimally invasive procedure itself is incapable of producing a permanent cure for FAH, leading to only a temporary breakdown of sweat gland innervation [10, 11]. Others propose that if surgery is performed too sparingly without aggressive removal of sweat glands, only inadequate sweat reduction is possible [7, 9].

The extent and anatomical distribution of recurrent axillary sweating have not been evaluated so far. Therefore, we initiated a study to evaluate the extent and distribution patterns of axillary sweating areas in patients who had undergone inadequate minimally invasive surgery.

Materials and Methods

Patients

Twenty-four patients (15 females, 9 males; median age = 27.8 years, range = 19–42 years) with FAH were enrolled in the study. All patients had undergone unsuccessful minimally invasive surgery for FAH prior to being recruited into the present study. Eighteen had unsuccessful superficial liposuction and six had liposuction curettage. Twenty-one patients were referred to our hyperhidrosis outpatient unit from other hospitals or private clinics and three had undergone surgery in our department. Fifteen patients reported recurrent bilateral sweating, whereas nine patients indicated that only one axilla was hyperhidrotic. This resulted in 39 axillae that were included in the present study.

Iodine Starch Test

To define the area of recurrent sweating, an iodine starch test was performed. To ensure that the iodine starch test findings were reproducible, every axilla was tested three times. For the starch test we used Lugol’s solution (also known as Lugol’s iodine), i.e., iodine, 1.0 g; potassium iodide, 2.0 g; and distilled water, 100.0 ml, a modification of the original Minor formulation [12]. Before testing, the axilla was dried thoroughly, painted with the iodine tincture, then air-dried and dusted with commercial potato flour. As the patient began to sweat, moistened starch reacted with the iodine to produce a vivid blue color. The size of hyperhidrotic area was quantified by using a transparent plastic foil with standardized grids (0.5 × 0.5 cm), enabling an exact measurement of the hyperhidrotic area in square centimeters [13]. Measurement was performed 60 s after application of the potato flour.

Results

Iodine Starch Test

The mean size of the recurrent hyperhidrotic area was 10.2 cm2 (range = 5.5–24.5 cm2). In the iodine starch tests, three different patterns of sweat area distribution could be distinguished: the crescent type (13 axillae, 33%), the circular type (16 axillae, 41%), and the spot-like form surrounding the insertions (10 axillae; 26%) (Fig. 1a–c). The crescent type occurred on the left side in 69% of those cases, always situated along the major pectoral muscle. The circular type was found equally on both sides around the hair-bearing axillary skin. The spot-like type was not uniformly distributed on both sides (70% right, 30% left) and presented as hyperhidrotic spots, each close to the insertion points of prior surgery.

Fig. 1
figure 1

a Crescent hyperhidrotic area situated laterally along the major pectoral muscle. b Circular-like recurrent hyperhidrotic area surrounding the hair-bearing axillary center. c Spot-like sweating areas located around the insertion points of the cannula. In all photos, the vivid blue color after iodine starch test indicates the hyperhidrotic area

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Discussion

For a permanent cure of axillary hyperhidrosis there are different surgical strategies reported in the literature, which can be divided primarily into local surgery and interruption techniques of the sympathic nerves (Table 1). The percentage of nonresponders to minimally invasive surgery, however, varies widely in the literature, ranging from 2% to 20% [2, 9]. Until today, the characteristics of recurrent axillary sweating and the extent of refractory hyperhidrotic areas have not been described in detail. This is due in part to inadequate methodology for evaluating the surgical outcome, making most results difficult to compare. Usually only subjective parameters such as the patient’s evaluation of symptoms are reported, whereas qualitative (e.g., iodone starch test) or quantitative (e.g., gravimetry) tests are often missing [1, 2, 4, 14].

Table 1 Classification of surgical strategies for focal axillary hyperhidrosis (FAH)
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Supporters of botulinum toxin A injections have recently expressed doubt that subcutaneous ablation of sweat glands is capable of permanent FAH reduction [10, 15]. They assume that minimally invasive strategies lead to only a temporary interruption of sweat gland innervation without removal of the glands themselves [10]. In contrast, supporters of surgical options believe that subcutaneous ablation techniques are efficient in removing sweat glands as shown by histologic studies, although inadequate surgery remains a possibility [8, 16].

A description of the recurrent sweating area could be helpful in assessing whether minimally invasive methods are inappropriate per se or whether an insufficient surgical performance might be responsible for the phenomenon of nonresponders. Interestingly, we showed that the central axillary region, which is normally the most secretory active area, did not reveal recurrent hyperhidrosis in any patient. Instead, three different patterns of recurrent sweat areas were identified: the crescent type, the circular type, and the spot-like form surrounding the insertion points of prior surgery. To explain the patterns we found, we assume that the surgeon focused mainly on the central axillary region, which is often the most hyperhidrotic area. The crescent type was always observed at the lateral aspect of the pectoralis muscle. The specific anatomical peculiarities of the peripheral axillary region could play a role in insufficient surgery. Our surgical experience confirms that the cupped depression between the pectoralis muscle and the axilla interferes with a subtle, careful curettage. Concerning the spot-like type, our surgical experience shows that the affected areas are difficult to reach by curettage, which is regularly performed in a fan-like fashion. The pressure that is necessary for the rasps of the cannula opening is not adequate around the insertion points; we feel that this is responsible for the spot-like pattern

On the one hand, our findings confirm that minimally invasive strategies are indeed capable of permanently reducing axillary hyperhidrosis. However, they also demonstrate that in the patients we studied, inadequate mapping of the FAH area and/or careless surgical technique may have occurred. Therefore, preoperative mapping of the hyperhidrotic area should be performed using an iodine starch test, followed by precise surgery of all identified sweating regions of the axillary skin.