The small nerve fibres that form a connection between the brain and several organs are responsible for autonomic functions. These are processes in the body that take place involuntarily, without conscious thinking. Impairment of small nerve fibres may lead to autonomic complaints, such as dry eyes or dry mouth, accommodation problems, increased or decreased perspiration, micturition problems, sexual dysfunction (such as impotence or decreased lubrication), diminished gastric emptying, diarrhoea or constipation, hot flushes and palpitations.

These complaints may also occur due to other conditions or as side effect of certain drugs. It is therefore important to exclude other causes for these complaints.