PRINCIPLES OF PAIN

Definition of pain
The International Association for the Study of Pain (IASP) gives the following definition:
Pain is ‘an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage’.

Figure 1: Origin of pain and pain perception

Types of pain
The cause of pain can be non-malignant or cancerous (malignant). Pain is classified according to the source of injury:
● Neuropathic – injury to tissue of the nervous system
● Nociceptive – injury to tissue other than nerve tissue

Neuropathic pain
Neuropathic pain is defined as pain initiated or caused by a primary lesion or dysfunction in the peripheral or central nervous system. Neuropathic pain is described as a ‘burning’, ‘tingling,’ ‘shooting’, ‘electric-like’ or ‘lightning-like’ pain. Neuropathic pain may persist for months or years beyond the apparent healing of any damaged tissues.
Neuropathic pain is commonly associated with several distinct characteristics. The first is unfamiliar or abnormal unpleasant sensations such as ‘lancing’ or ‘burning’ pain, which are called dysesthesias. Persistent allodynia, pain resulting from a non-painful stimulus such as light touch, is also a common characteristic of neuropathic pain. Partial sensory deficit, for example, diminished perception of certain stimuli such as heat or cold, is also seen in patients with neuropathic pain. Finally, neuropathic pain is characterized by hyperpathia, which occurs when the pain message from a normally painful event is exacerbated so that greater pain is felt. Neuropathic pain can be effectively treated with neurostimulation

Nociceptive pain
Nociceptive pain is caused by an acute tissue injury or disease outside of the nervous system. It is often an on-going ‘dull ache’ or ‘pressure’, rather than the sharper, trauma-like pain more characteristic of neuropathic pain.
Examples of nociceptive pain include sprains, bone fractures, burns, bumps, bruises, postoperative pain, and inflammation from an infection or arthritic disorder. Nociceptive pain can be effectively treated with intrathecal drug delivery
There are two types of nociceptive pain (Table 1):
● Somatic nociceptive pain
● Visceral nociceptive pain

Table 1: Differences between somatic and visceral nociceptive pain
Somatic nociceptive pain		Visceral nociceptive pain
Location	Localized	Diffuse
Sensation	Continuous, aching, throbbing and gnawing	Deep, continuous, dull and vague
Cause	Destruction, invasion, or irritation of skeletal muscles, tissue, bone and blood vessels	Injury to the viscera such as internal organs of the cardiovascular and respiratory system, the gastrointestinal tract and the reproductive and urinary tracts

What’s Up
	August/14/2007 Inomed ISIS Intraoperative neurophysiological monitoring started to function in all our related surgeries.

	Oct /07/2009 The author celebrating 30 years experience in neurosurgery.
	Nov/28/2013 Skyra 3 tesla magnetom with all clinical applications are running in the neurosuite.
	Nov/28/2014 Inomed MER system for DBS and lesioning is running in the neurosuite.