Management of pain in dermatology

“Pain is both unique and universal, and it is a reminder of man’s vulnerability. Pain is a symbolic anticipation of death. All cultures without distinction have tried to find a meaning to pain through their traditions [1]”. Management of pain is a public health objective.

1 - DEFINITIONS AND PATHOPHYSIOLOGICAL MECHANISMS

According to the International Association for the Study of Pain (IASP) “pain is an unpleasant sensory and emotional experience associated with actual or potential tissue damage or described in terms of such damage”. All pain is made up of several components, i.e. sensory, affective, cognitive and behavioural. Damage to tissues leads to the release of several groups of mediators that activate or control the activation threshold of nociceptors, i.e. bradykinin, H⁺ and K⁺ ions, serotonin, histamine, prostaglandins, leukotrienes and neuropeptides (substance P, CGRP and VIP). Originating in the free nerve endings of the skin, the afferent Ad (small diameter, myelinated) or C (non-myelinated) fibres carry pain signals to the posterior horn of the spinal column and create a synapse there. Two types of mediators intervene predominantly, i.e. excitatory amino acids and peptides, including substance P [2].

The neurons of the posterior horn transmit information to the reticular formation of the brainstem (imprecise and poorly localised information) and the central, posterior, lateral and medial subdivisions of the thalamus (sensory-discriminative information). The pain signals then arrive at the cortex, giving rise to a sensation of pain. The body also possesses an endogenous pain control system consisting of descending inhibitor supramedullary neurons. The neurons are capable of modulating the medullary transmission of the pain signal. Inhibition is mediated by noradrenaline and serotonin generated in the brainstem.

Pain can be divided into two categories as follows:

– acute pain is considered as an “alarm signal” heralding damage threatening the tissues. Acute pain is a symptom of a physical disorder, lesion or disease. Patients should receive treatment for the cause of the pain and be given analgesics if necessary depending on the intensity of the pain;

– chronic pain is characterised by the occurrence of pain for more than three months. Patient presenting with chronic pain cannot simply be given symptomatic treatment. Correcting the underlying disorder may be an essential preoccupation which may require the skills of a multidisciplinary team consisting of the attending physician, a pain specialist and a psychotherapist.