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Neuropathic pain: what to look for in primary care

Nigel Higson
MA BM BCh DRCOG
General Practitioner
Hove
East Sussex

Many people come to us complaining of pain. It is one of the most common presenting symptoms in primary care and a symptom for which there can be a host of causes. Some causes of pain are obvious - a broken finger, bruising, a wrenched back. Some causes are less obvious and include a host of anatomical and physiological disturbances that can make treatment less easy. Often with pain there is a considerable interplay with the patients psychological state - some have what we term "a low pain threshold", others tolerate considerable pain,depending not only on their previous experiences, but also on cultural origins and language difficulties.

What is neuropathic pain?
There are a number of different types of pain. Nociceptive pain is a natural and appropriate physiological response to a painful stimulus, for example the pain from an injury or a burn. It is usually shortlived, with a time course of less than three months, and results from tissue damage. Nociceptive pain will decrease with healing of the primary injury. Response to standard analgesia is good and is psychologically accepted by the patient as they can understand the ­origin of the pain.
Neuropathic pain, however, is an inappropriate response caused by a primary lesion or dysfunction of the nervous system. It results from damage within the peripheral nervous system to the neurons themselves; there are anatomical and physiological changes within the dorsal root ganglia and dorsal horns of the spinal cord that change the pain inhibitory mechanisms from the central nervous system (CNS). Such damage may result from viral or metabolic damage (as in diabetes,  shingles and HIV). Pain persists for years, and the patient is not necessarily able to understand the origin of the pain, which results in less acceptance and increased distress. Secondary depression is common coupled with chronic sleep disturbance. Discussion and explanation of the different types of pain and the ways in which the patient responds to them is a key step in helping the patient cope with his/her symptoms.
Neuropathic pain is often described as an intermittent shooting or penetrating pain with electric shock-like pains. There are unpleasant abnormal sensations that are not painful (paraesthesia) together with unpleasant abnormal sensations that are painful (dysthetic pain). Coupled with these are secondary morbidities consequent to the neuropathic pain:

  • Sleep interference.
  • Reduced quality of life.
  • Reduced memory retention.
  • Mood swings.
  • Depression.
  • Anxiety.
  • Anorexia.
  • Loss of libido.
  • Apathy.
  • Despair and isolation.
  • Suicidal tendencies.

Untreated, or treated inappropriately, neuropathic pain will not only worsen, as measured on any form of pain scale or questionnaire, but the patient will also develop more and more of the associated secondary morbidities. There will be increased dissatisfaction with the medical profession, and the patient may go to inappropriate therapists in an attempt to relieve the pain. There are many accounts of limbs being amputated in attempts to relieve pain - always unsuccessful as the pain mechanism arises within the spinal cord.

Causes of neuropathic pain
Many patients experiencing neuropathic pain will have one condition being the ultimate cause of that pain - all these causes can be seen to have damaged the nerve structure or function in some way. Poor recognition of the symptoms of neuropathic pain and inappropriate treatment will result in delays and suffering for the patient. If there is no obvious nociceptive cause for the pain, then the practitioner would be wise to consider neuropathic pain, such as:

  • Diabetes (peripheral diabetic neuropathy).
  • Poststroke pain.
  • Postsurgery pain.
  • Alcohol-induced neurotoxicity.
  • HIV - both secondary to the infection and to the treatment.
  • Trigeminal neuralgia.
  • Postherpetic neuralgia.
  • Multiple sclerosis (MS).
  • Nutritional.
  • Neurotoxic effects.
  • Phantom limb pain.
  • Chronic sciatica.
  • Spinal cord injury.

Perhaps the best tools for the practitioner in dealing with neuropathic pain are confidence and empathy. The patient needs to be brought on board and helped to understand that the pain they are feeling in their foot will not respond to the foot being removed! Simple explanations of neurophysiology - how nerve impulses are conducted across synapses and how such electrical changes are interpreted by the brain - can help with the discussion about prescribing drugs which change that transmission. An understanding that there is secondary morbidity and that being in chronic pain can cause family stress will encourage the patient to express themselves more fully and work with the medical or nursing practitioner to find a means to modify the pain.
Nursing assessment of a patient should not only include appropriate questioning about the pain if the patient volunteers that he or she is in discomfort, but also proactive discussion for those patients in the risk group for neuropathic pain - patients with diabetes being seen for monitoring; those nursed with shingles; and stroke or MS patients being supported at home or in hospital. The opportunity to discuss strange sensations that the patient is suffering may reassure them that they are not developing some other complicating morbidity such as cancer. Neuropathic pain and painless neuropathy are often underdiagnosed and often require someone assessing afresh or thinking more laterally to make a link between the symptoms and the underlying morbidity.
Shingles is a very common cause of neuropathic pain that may present to nurses in preference to medical practitioners. The development of a typical shingles rash (unilateral, blistering, painful rash) requires urgent action to try to diminish the risk of postherpetic neuralgia. The use of antiviral drugs and simple analgesics and the prescription of antineuropathic drugs such as amitriptyline should all be instigated as soon as the diagnosis is confirmed.
In the case of diabetic peripheral neuropathy, any attempt to control neuropathic pain must be in parallel with efforts to maximise control of the diabetes itself and thus lessen further neuronal and metabolic damage.

Drug management
Although drug management of neuropathic pain may not be in the control of the nurse, much can be done to assist with the other comorbidities as outlined above. There should also be awareness that many of the drugs that are used do have significant side-effects and these may well be the cause of patient presentation. Amitriptyline is widely used within Europe for modifying pain-nerve activity; dry mouth, constipation, sleepiness, cardiac rhythm abnormalities are not uncommon side-effects. Drugs such as pregabalin or gabapentin may make the patient feel "out of it" or unstable with mild giddiness. Visual disturbances and dizziness may occur with carbamazepine, which is commonly used to treat trigeminal neuralgia.
The greatest problem with using drugs that were primarily designed for other purposes (depression with amitriptyline, epilepsy with carbamazepine) is the patient information leaflet, or a chance remark by the pharmacist when the patient asks what the drug is for. It is essential when talking with patients about the medication that an explanation is given about the use of the drug for a purpose that may not be described in the patient information leaflet contained in the medication packaging.
Nurses are in a prime position to recognise signs or symptoms of neuropathic pain, to support the patient in understanding the causes of the pain, and to bring such patients to the attention of the appropriate medical practitioner.

Resources
The Neuropathy Trust
A very good ­independent organisation/self-help group that has developed to assist patients with the ­understanding of neuropathic pain.
They publish useful booklets on the origins, causes and management of neuropathic pain
T:01270 611828
E:info@neuropathy-trust.org
W:www.neuropathy-trust.org