Hyperhidrosis

1

What is hyperhidrosis?

Hyperhidrosis is defined as sweating and flushing in response to heat or emotional stimuli in excess of that required for normal thermoregulation.

It most commonly affects the palms, soles and axillae.

2

What is the anatomy of the sympathetic chain (Figure 1)?

The left and right sympathetic chains consist of 23 paired sympathetic ganglia (three cervical, twelve thoracic, four lumbar and four sacral) interconnected by nerve fibres.

The thoracic sympathetic ganglia measure 1-2mm in diameter and lie just beneath the parietal pleura over the neck of each rib, in close proximity to the spinal column on the posterior thoracic wall.

The stellate ganglion represents fusion of the inferior cervical ganglion and the 1st thoracic ganglion.

The 2nd thoracic sympathetic ganglion is located just above the confluence of the azygos vein and superior vena cava on the right, and just above the aortic arch on the left.

Occasionally, there may be aberrant anatomy, such as double sympathetic chains.

3

What is the physiology of sweating?

Thermoregulation is coordinated via the cerebral cortex, hypothalamic pre-optic sweat centre and sympathetic chain, with:

a)

sensory afferents conveying heat or emotional stimuli to the central nervous system;

b)

efferent post-ganglionic fibres connecting the sympathetic chain to the sweat glands.

The 1st thoracic sympathetic ganglia is responsible for facial sweating, 2nd and 3rd for palmar sweating and 4th for axillary sweating.

The purpose of sweating is heat loss, with physiological sweating ranging from 0.75-10L/day, depending on the number of apocrine and eccrine sweat glands that are activated, such as by increased temperature or exercise.

Eccrine glands are located all over the body and secrete sweat directly onto the skin via pores, whereas apocrine glands are located in hair-dense areas of the body, such as the axillae and groin, and secrete sweat via hair follicles.

In hyperhidrosis, the sweat glands are activated in excess of that required for normal thermoregulation.

4

How is hyperhidrosis classified?

Localised hyperhidrosis – palmar, plantar, gustatory, cervical, axillary, thoracic or abdominal.

Generalised hyperhidrosis.

Emotionally induced hyperhidrosis – which affects the palms, soles and axillae.

5

What is the aetiology of hyperhidrosis?

Primary (idiopathic) – which represents over-activity of the sympathetic nervous system.

Secondary hyperhidrosis – which appears to be more generalised and can be caused by:

a)

neurological disorders – peripheral neuropathy, Parkinson’s disease, spinal cord injuries, reflex sympathetic dystrophy;

b)

metabolic disorders – thyrotoxicosis, diabetes mellitus, phaeochromocytoma, hyperpituitarism, pregnancy, carcinoid syndrome;

c)

infections – tuberculosis;

d)

malignancy – lymphoma, leukaemia;

e)

chronic alcoholism;

f)

medications – cholinesterase inhibitors, opioids, tricyclic antidepressants, selective serotonin reuptake inhibitors.

6

What is the epidemiology of hyperhidrosis?

Its prevalence is estimated around 1-2% in the general population, but occurs 20 times more frequently in the Japanese population.

It affects men and women in an equal distribution.

Localised hyperhidrosis usually presents at puberty whereas the generalised form usually occurs in adulthood.

7

What are the clinical features of hyperhidrosis?

The clinical features suggestive of a diagnosis of primary hyperhidrosis include:

a)

excessive sweating >6 months’ duration;

b)

primarily affecting eccrine-dense sites, such as the axillae, palms, soles and face;

c)

bilateral and symmetric distribution;

d)

episodes occurring at least once a week;

e)

absent nocturnally;

f)

onset at age <25 years;

g)

positive family history;

h)

impairment of daily activities, such as patients nervous of greeting people with a handshake, unable to grip strongly or frequent changes of clothing per day.

The severity of hyperhidrosis may be quantified by the Hyperhidrosis Disease Severity Scale (HDSS) (Table 1).

8

What is Harlequin syndrome?

Harlequin syndrome is a rare autonomic disorder characterised by reduced flushing and sweating of half of the face, neck and upper chest, in response to heat or exercise.

It may occur following unilateral injury to the sympathetic chain, resulting in the:

a)

ipsilateral half of the body becoming denervated;

b)

contralateral half of the body becoming hyperactive.

9

What is Frey’s syndrome?

Frey’s syndrome represents a disorder in which there is sweating and flushing in the cheek area in response to stimuli that would normally cause salivation, such as the smell, sight or taste of food (gustatory sweating).

It may occur as a complication of parotid gland surgery (secondary to facial nerve injury) or thoracic sympathectomy (due to aberrant neural regeneration).

10

What are the investigative findings of a patient with hyperhidrosis?

Ninhydrin sweat test – which demonstrates functioning sweat glands as printed dots on special paper, as ninhydrin stains amino acids and peptides contained in sweat with great sensitivity. It can be used as a qualitative assessment of palmoplantar hyperhidrosis to monitor the progress before and after treatment.

Minor starch iodine test – where sweat causes dark blue staining when the skin is pressed against special paper. It can also be used for mapping focal hyperhidrosis.

Gravimetric testing – which involves measuring the collection of sweat, using filter paper of a known weight, over a fixed period of time at rest, after exposure to heat and after treatment.

11

What are the therapeutic options for a patient with hyperhidrosis?

Conservative:

a)

topical aluminium chloride;

b)

intradermal botulinum toxin injection;

c)

systemic anticholinergic agents or beta-blockers;

d)

tap water iontophoresis – passing a direct current across the skin.

Surgical:

a)

endoscopic thoracic sympathectomy (open surgery is rarely performed);

b)

subcutaneous excision of axillary sweat glands (using curettage or liposuction).

12

What are the principles of management of a patient with hyperhidrosis?

Once the diagnosis has been established, particular attention should be made to identify any secondary causes of hyperhidrosis.

Initially, patients with all stages of disease severity are managed using the least invasive treatment options, such as topical aluminium chloride.

Systemic medications may be used for patients with generalised hyperhidrosis.

Tap water iontophoresis is reserved for patients with palmoplantar hyperhidrosis.

Botulinum toxin injections are generally used for patients with axillary hyperhidrosis.

Percutaneous sympathectomy is a minimally invasive procedure similar to the botulinum method, where nerve block is obtained with injection of phenol. The procedure provides temporary relief and is used in some cases before progressing to permanent surgical sympathectomy.

Endoscopic sympathectomy is usually performed in patients with primary focal hyperhidrosis after conservative methods have failed.

13

What are the principles of a thoracic sympathectomy for a patient with hyperhidrosis?

The primary aim of a sympathectomy in the management of hyperhidrosis is to interrupt the transmission of impulses from the sympathetic nervous system to the sweat glands.

Under general anaesthesia with a double-lumen endobronchial tube, single-lung ventilation is obtained, with CO₂ insufflation to aid visualisation.

The patient is placed in a semi-Fowler’s position (arms abducted and a roll behind the shoulders), which uses gravity to displace the lungs downwards and away from the upper posterior chest wall.

Either a single-port technique, with an operating thoracoscope, or a two-port technique, with a separate camera and dissecting instruments, can be used.

The thoracic sympathetic ganglia are identified running over the necks of the ribs under the parietal pleura in the superior part of the posterior chest wall (Figure 2).