Types of Neuropathic Pain (NP) – and Epidemiology


Neuropathic pain can be subdivided according to the structure involved, e.g. a peripheral nerve, nerve root or the central nervous system (spinal cord, brain). It appears to serve no useful function, and is an abnormal condition. It is often difficult to diagnose and treat. NP is routinely classified according to the anatomical location of the lesion as well as the underlying cause of the disorder, with the majority of patients falling into four broad categories: painful peripheral neuropathies (in some circumstances also called localized neuropathic pain2), central-pain syndromes, mixed-pain syndromes, and complex painful neuropathic disorders.1

Based on the fact that averaging across all neuropathic pain conditions, physicians reported that approximately 60% of patients had Localized neuropathic pain (LNP) an expert group has proposed a first nucleus for a definition for LNP based on the International Association for the Study of Pain (IASP) definition of neuropathic pain: LNP is a type of neuropathic pain characterized by a circumscribed and consistent area of maximum pain.2

Peripheral neuropathies originate from damage to the peripheral nerve, plexus, dorsal root ganglion, or root. Examples include post-herpetic neuralgia (PHN), diabetic polyneuropathy (DPN), phantom-limb pain, painful scars, human immunodeficiency virus (HIV)-associated polyneuropathy, and trigeminal neuralgia.1

 

 

Epidemiology and risk factors of Post-Herpetic Neuralgia (PHN)

PHN is a form of neuropathic pain that can occur after rash healing in persons infected with herpes zoster, an acute viral infection also known as shingles.3

Primary infection with the varicella zoster virus  (VZV) causes chickenpox, which affects 90% of children by the age of 15.4

Following primary infection, the virus typically remains dormant in the dorsal root ganglia, but may become reactivated to cause herpes zoster.4

According to a report of the International Association for the Study of Pain (IASP) of 1994, the lifetime incidence of herpes zoster is 10–20% of the population.4

Among all patients with herpes zoster, 9-14% develop PHN.2 This incidence increases to 20–50% in patients over 50 years of age.

 

Epidemiology and risk factors of Diabetic Polyneuropathy (DPN)5–14

In 2000, more than 171 million people were affected with diabetes worldwide.12

Among patients with diabetes, an estimated 16-50% have DPN,2-6 although up to 50% of cases may be asymptomatic.5, 8

Where DPN is present, 10-20% of patients may experience troublesome sensory symptoms requiring treatment,5 although significant levels of pain may be present in many more. In a study cited by Schmader, the average pain intensity among 105 diabetics with DPN was 5.75 on a scale of 0-10, where 0 = no pain and 10 = worst possible pain.6 Schmader also reports that, in patients with diabetes, the occurrence of neuropathy increased from 6% at baseline  to 20% over a 10-year follow-up period.6

Risk factors for developing DPN include the degree and duration of hyperglycaemia, smoking, and comorbid retinopathy and nephropathy.9

Some studies suggest that the prevalence of both PHN and DPN is expected to increase.10, 11, 13

 

References
1 Baron R. Neuropathic pain: a clinical perspective. Handb Exp Pharmacol. 2009; 194:3-30.
2 Mick G, et al. What is localized neuropathic pain? A first proposal to characterize and define a widely used term. Pain Manag. 2012 Jan;2(1):71-7.
3 Dworkin RH, et al. Impact of postherpetic neuralgia and painful diabetic peripheral neuropathy on health care costs. J Pain. 2010; 11:360-8.
4 Mohamed SA et al. Pain: Clinical Updates. 1994;2:1-8.
5 Boulton AJ, et al. Diabetic somatic neuropathies: a technical review. Diabetes Care. 2004;27:1458-86.
6 Schmader KE. Epidemiology and impact on quality of life of postherpetic neuralgia and painful diabetic neuropathy. Clin J Pain. 2002;18:350-4.
7 Daousi C et al. Chronic painful peripheral neuropathy in an urban community: a controlled comparison of people with and without diabetes. Diabet Med. 2004; 21:976-82.
8 Boulton AJ et al. Diabetic neuropathies: a statement by the American Diabetes Association. Diabetes Care. 2005; 28:956-62.
9 Zochodne DW. Diabetes mellitus and the peripheral nervous system: manifestations and mechanisms. Muscle Nerve. 2007;36:144-66.
10 Reynolds MA et al. The impact of the varicella vaccination program on herpes zoster epidemiology in the United States: a review. J Infect Dis. 2008; 197 (Suppl 2):224-7.
11 Sadosky A et al. A review of the epidemiology of painful diabetic peripheral neuropathy, postherpetic neuralgia, and less commonly studied neuropathic pain conditions. Pain Pract. 2008; 8(1):45-56.
12 Wild S et al. Global prevalence of diabetes. Estimates for the year 2000 and projections for 2030. Diabetes Care. 2004; 27:1047-53.
13 Dworkin RH, et al. Impact of postherpetic neuralgia and painful diabetic peripheral neuropathy on health care costs. J Pain. 2010; 11:360-8.
14 Barrett AM et al. Epidemiology, public health burden, and treatment of diabetic peripheral neuropathic pain: a review. Pain Med. 2007; 8:50-62.