Pain
Types of Pain
Pain can be divided into three subtypes, each with their own mechanisms, symptoms and treatments.
Acute Pain
Acute pain is the direct result of Nociceptor activity within the Nervous System. It can be excruciating but fortunately is not long lasting (4-5 days post-stimulus). This type of pain is usually self-resolving with tissue healing and can be easily treated with standard analgesics such as opioids and Non-Steroidal Anti-Inflammatory Drugs (NSAIDs). Migraine falls under this category of pain.
Chronic Pain
Unlike acute pain, chronic pain is a major clinical condition; it is usually the result of inflammation, for example in arthritis, or space-occupying lesions (tumours). Like acute pain it is also a result of nociceptor activity but it is more prolonged, lasting a minimum of 3-6 months. This type of pain can be self-resolving but it is often not; treatment is similar to that with acute pain but the long-term nature of the condition can pose problems such as dependency. Chronic pain can also lead to behavioural changes, for example depression and changes in posture to protect the affected area.
Neuropathic Pain
Also known as Neurogenic Pain, it is a result of peripheral or central nerve damage, caused by either direct trauma or illness. Central lesions can produce a similar effect. Neuropathic pain is long lasting and episodic; it can be very severe and is not necessarily the result of nociceptor activity. Treatment of such conditions is variable, a third of affected patients can be successfully treated with Tricyclic Antidepressants, eg Despiramine, and a further third can be treated successfully with Anticonvulsants, eg Gabapentin, however both of these are effective at levels lower than those used for their traditional usage. The remaining third of affected patients is unfortunately untreatable. The condition can also result in depression and other behavioural problems. Pathological Pain, often associated with Neurogenic Pain but it can be distinct, is due to an abnormal functioning of the pain system. [32, 40]
