Introduction

Hyperhidrosis (HH) is an excessive sweating disorder that affects 2.8% of the population in the United States alone. By definition, HH is sweating beyond what is expected for environmental conditions and thermoregulation. In practice, it is considered sweating that significantly interferes with daily life. Not only does it cause anxiety and emotional distress for those who suffer from it, but it can also be a risk factor for cutaneous infection, eczematous dermatitis, and muscle cramps. Lear et al reported that most patients who have HH experience it in areas of high eccrine density such as the axillae (51%), soles (30%), palms (24%), and occasionally in the craniofacial area (10%). Multiple modalities are available for treatment of primary focal HH, from topical medications such as aluminum chloride, to non-surgical approaches such as iontophoresis and botulinum toxin injections, to systemic medications such as clonidine and even surgical sympathectomy. In this chapter, we will discuss the role of botulinum toxin in the treatment of HH of the palms and soles.

Patient evaluation

Most patients who present with palmar HH have had the condition since childhood or early adolescence with no known cause and report ‘sweaty palms’ that cause them social embarrassment. Solish & Haider reported evidence suggesting that an autosomal dominant inheritance pattern with variable expressivity such that a child born to a parent with palmar HH has a 25% chance of developing the disorder as well. Patients will go to great lengths to avoid shaking people’s hands and often keep their hands in their pockets. The hyperhidrosis can be so severe as to cause actual physical dripping and maceration and peeling of the skin itself (Fig. 24.1). Similarly, patients with plantar hyperhidrosis will report the need to change socks frequently or that they ‘slip’ in their shoes while walking. Interestingly, a study by Lear and colleagues suggested that spontaneous regression might occur over time as there is a low prevalence of the disorder in the elderly population. It is important for the physician to keep in mind the severe psychological impact HH has on patients, many of whom do not seek treatment due to embarrassment and yet decrease their leisure activities and suffer from depression because of it.

Figure 24.1 Severe palmar hyperhidrosis.

Prior to treatment, it is important to take a careful clinical history to ensure that the patient suffers from primary, not secondary, hyperhidrosis. In secondary hyperhidrosis, medications or systemic health problems can be responsible for sweating (Box 24.1) and the condition is usually generalized. If there is a suspicion of secondary hyperhidrosis, a complete blood count, fasting glucose level and thyroid function test are preliminary laboratory tests to be ordered.

In primary hyperhidrosis, neither the number, density, nor size of eccrine glands is abnormal; rather there is overactivity of the postganglionic sympathetic cholinergic fibers innervating them. For this reason, botulinum toxin type A can be effective in treatment; the toxin inhibits presynaptic release of acetylcholine and binds to acetylcholine receptors at the postsynaptic membrane thus disrupting sympathetic input to eccrine glands. Because eccrine glands are found in a high concentration in the axillae, palms, soles, and forehead, these are the areas where primary focal HH typically presents as excessive sweating for at least 6 months’ duration. To make a positive diagnosis of focal primary HH, Hornberger stated that the patient should also present with at least two of the following criteria: age at onset younger than 25 years, frequency of at least one episode per week, a positive family history, cessation of sweating upon sleep, impairment of activities of daily living, and a distribution that is bilateral and relatively symmetric. Of note, Hamm et al found that palmar hyperhidrosis can present unilaterally in 6% of cases.

Scoring the impact of hyperhidrosis on the patient’s quality of life is important as well, not only to gauge treatment success but also to aide in obtaining insurance approval for treatment. The Hyperhidrosis Disease Severity Scale (HDSS) is a quick diagnostic tool that the practitioner can administer during the examination and was found by Solish and colleagues to be a reliable means of assessment (Table 24.1). HDSS scores should be followed to guide the choice of treatment and to determine whether treatment has made an impact (success should be considered a reduction in HDSS of 1 or more).

Table 24.1 Hyperhidrosis disease severity scale

General considerations

Treatment of palms and soles for primary focal HH is considered an off-label use of neurotoxin. In the United States, botulinum toxin type A (which is FDA approved for treatment of axillary HH) is commercially available as Botox^® (Allergan, Irvine, CA, USA), Dysport^® (Medicis, Scottsdale, AZ, USA), and Xeomin^®