Neuropathic Pain

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Definition

Complex type of pain initiated or caused by a primary lesion or dysfunction in the nervous system (IASP, 2012).

“pain initiated or caused by a primary lesion or dysfunction in the nervous system.” One example of neuropathic pain is called phantom limb syndrome.

Cause

Damage can be caused by trauma, surgery or disease processes including diabetes,infection (eg after shingles infection - post-herpetic neuralgia) and cancer.

Has a peripheral origin and may develop central sensitization but "primary afferent input is critical for maintaining neuropathic pain in peripheral nerve injury and distal polyneuropathy"

Pain may be generated in peripheral nerve, dorsal root ganglion,There are many reasons that patients may develop neuropathic pain. However, on a cellular level, one explanation is that an increased release of certain neurotransmitters which signal pain, combined with an impaired ability of the nerves to regulate these signals leads to the sensation of pain originating from the affected region. Additionally, in the spinal cord, the area which interprets painful signals is rearranged, with corresponding changes in neurotransmitters and loss of normally-functioning cell bodies; these alterations result in the perception of pain even in the absence of external stimulation. In the brain, the ability to block pain can be lost following an injury such as stroke or trauma. Over time, further cellular damage occurs and the sense of pain persists.

Trigeminal neuralgia.
Pain following shingles (postherpetic neuralgia).
Diabetic neuropathy - a nerve disorder that develops in some people with diabetes.
Phantom limb pain following an amputation.
Multiple sclerosis.
Pain following chemotherapy.
HIV infection.
Alcoholism.
Cancer.
Atypical facial pain.
Various other uncommon nerve disorders.

Assessment

Assessing neuropathic pain

Step 1. A clinical history of disease or lesion of the somatosensory system suggests a possible diagnosis of neuropathic pain Step 2. Confirmation by either clinically reproducible signs or investigations would suggest a probable diagnosis of neuropathic pain Step 3. If the history, clinical examination and investigations are positive, this would support a definite diagnosis of neuropathic pain

Adapted from Treede RD, Jensen TS, Campbell JN, et al. Neuropathic pain: redefinition and a grading system for clinical and research purposes. Neurology 2008;70:1630–5

Sensory examination - light touch, temperature, painful stimulus, vibration and proprioception. Motor testing tone, strength, reflexes and coordination. Look for autonomic changes in colour, temperature, sweating and swelling.

Examination of a Patient with Peripheral Neuropathic Pain shows a real patient with multiple mononeuropathy due to isolated peripheral nervous system vasculitis. He is suffering from neuropathic pain in his left hand and both legs. Functional assessment and sensory and motor examination of both upper and lower limbs is demonstrated

DN4 – QUESTIONNAIRE Assists with neuropathic pain assessment

Use when neuropathic pain is suspected.

Please complete this questionnaire by ticking one answer for each item in the 4 questions below.

Interview Of The Patient

Question 1: Does the pain have one or more of the following characteristics?

1: Burning Yes No 2: Painful Cold Yes No 3: Electric Shocks Yes No

Question 2: Is the pain associated with one or more of the following symptoms in the same area?

4: Tingling Yes No 5: Pins and Needles Yes No 6: Numbness Yes No 7: Itching Yes No

Examination Of The Patient

Question 3: Is the pain located in an area where the physical examination may reveal one or more of the following characteristics?

8: Hypoesthesia to touch Yes No 9: Hypoesthesia to prick Yes No

Question 4: In the painful area, can the pain be caused or increased by:

10: Brushing ? Yes No

TO COLLATE: •Score 1 to each YES answer •Score 0 to each NO answer •If the score is 4 or higher then the pain is likely to be neuropathic pain. •If the score is less than 4 then the pain is unlikely to be neuropathic pain

Ref : Bouhassira D, Attal N, Alchaar H, et al. "Comparison of pain syndromes associated with nervous or somatic lesions and development of a new neuropathic pain diagnostic questionnaire (DN4)." Pain 114.1-2 (2005): 29-36.