Neuropathic or nerve pain arises as a result to damage or improper functioning of the nerves/nervous system. It presents as poorly localised burning, shooting or electric shock like pain with altered sensitivity in the affected area. Sudden increase in pain severity is commonly observed. Over the period of time sometimes skin changes, weakness and wasting of muscles can develop. The affected area may develop increased sensitivity perceiving non painful stimuli such as touch to be painful. Alternatively patient may report having pain in areas which feel numb. Some examples of common conditions with neuropathic pain include
- Diabetic Neuropathy where patients complain of a burning sensation most commonly in the sole of feet, worst at night time
- Infections such as Post heretic neuralgia, HIV
- Persistent post surgery pain or trauma involving nerve damage
- Drug induced neuropathy including that after chemotherapy/radiotherapy
- Cancer related neuropathy
- Post Amputation- Phantom limb pain
- Central causes such as spinal cord injuries, strokes, multiple sclerosis
- Complex Regional Pain Syndrome
- Nutritional deficiencies
Screening questionnaires are commonly used in diagnosing neuropathic pain. Investigations such as blood tests, scans, and nerve and muscle tests may be requested to confirm the diagnosis or rule out other conditions. Depending on the history, examination and investigation findings the pain condition is diagnosed as possible, probable or definite neuropathic pain.
Neuropathic pain can be severe with significant impact on the quality of life. Sleep disturbances, anxiety and depression are frequently observed along with pain. Multi-disciplinary approach has the advantage of addressing all concomitant factors involved in exacerbating pain and affecting quality of life. Some of the common interventions include
Drugs labelled as Neuropathic agents are specifically used to treat pain neuropathic pain. Whilst they may have been made to treat other conditions (like epilepsy and depression) it is not uncommon for drugs to be used for multiple conditions. A number of anticonvulsants and antidepressants are well reorganised pain killers for nerve pain. Examples of these drugs include Gabapentin, Pregabalin, Nortiptyline etc. Please follow the link to medication optimisation to find out more.
Nerves carry the pain sensation to the brain and blocking this transmission can be achieved by nerve blocks. These are useful when the pain generator are the nerves themselves and in conditions where the focus is on reducing pain, improving quality of life. An example of this is persisting knee pain after joint replacement surgery despite there being no problem with the replaced joint. In such cases Genicular nerves which carry pain sensation from the knee are targeted to reduce pain. It is important to understand that persisting pain does not always signify ongoing damage. The nerves targeted will depend on the area involved and may include sympathetic nerves as in Sympathetic blocks e.g. stellate ganglion block, Hypogastric plexus block.
Transmission of pain impulses to brain can also be reduced by other interventions such as radiofrequency treatment and Neurolytic blocks. Further details of this are mentioned in other sections of this website depending on the body part involved such as for shoulder pain further information about suprascapular nerve can be found in the joint pain section.
Some drugs when given through the veins over a period of time can produce prolonged pain relief when the source of pain is the nerves/nervous system. These drugs can help to reduce the sensitivity of nerves at the site of lesion and in spinal cord which in turn leads to reduced pain sensation being transmitted to brain.
As nerve injury /dysfunction may be accompanied by weakness/ atrophy of muscles, physiotherapy forms an essential pillar of overall management. It helps in preventing deconditioning of muscles and preserving the functionality. Please follow the link for finding out more about how physiotherapy can help.
Options including cognitive behavioral therapy, coping strategies and relaxation techniques can help in dealing with flare up episodes and any accompanying mood disturbances. Please follow the link for finding out more about how psychology can help.
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Postherpetic Neuralgia (PHN)
Herpes Zoster is caused by the reactivation of the same virus which causes chickenpox. If you have had chickenpox before, the virus lies inactive in the nervous system till the time it gets an opportunity (such as in old age or when body’s immunity is reduced) to spread along the nerve. This produces the typical rash of Herpes Zoster accompanied by pain, numbness, itching, skin pigmentation and sometimes scarring. One out of five patients goes on to develop PHN where the pain persists for more than 120 days after the onset of rash. PHN is rare in age group below 50 years and incidence increases after the age of 60 years. Risk factors for PHN or persisting pain include older age and widespread rash with severe pain at onset.
Pain character in PHN is generally burning, shooting, throbbing or electric shock like and this may occur spontaneously or in response to stimuli. It is most commonly observed in chest wall region (thoracic dermatomes) and in the distribution of ophthalmic branch of the trigeminal nerve (around the eye). You may find pain is more severe at night time and during periods of stress. It is often accompanied by hypersensitivity of the involved area. In some cases muscle weakness may be present. About half of the patients recover within a year and in the remaining the course is variable. In one study it was observed that the proportion of patients with spontaneous resolution of pain decreased with increasing time since the onset of herpes zoster.
Prevention of PHN is important and includes vaccination, early use of antiviral agents. Acute pain control at the time of onset is important. In selective cases oral steroids are considered. Those with persisting pain can be challenging to treat and Multi-disciplinary approach is preferred. Drug combination therapy is often used with a combination of systemic medications and topical agents (gels/patches /creams). Unfortunately some of the topical options such as 8% capsaicin patch, 5% lidociane patch are not available in India currently.
Apart from medications Interventions/ injections such as nerve blocks, drug infusions, neuromodulation are reasonable option to consider. Sympathetic nerve blocks including stellate ganglion block are often used. Most evidence suggesting short-term benefits and hence they may need to be repeated. It is important to address any concomitant psychological factors and maladaptive coping mechanisms.
Complex Regional Pain Syndrome (CRPS)
CRPS is one of the causes of persisting limb pain. It can occur after surgery or injury and sometimes the injury is so trivial that you may not even remember it. In other cases the injury may be more severe with or without nerve damage. The pain however lasts much longer and is more severe than expected. It can range from mild self-limiting to chronic debilitating condition affecting activities of daily living and quality of life. The reason why CRPS develops is unclear and multiple mechanisms are thought to be involved. A combination of signs and symptoms is used to make the diagnosis as there is no specific diagnostic test. Investigations are helpful to exclude other conditions such as infection and rheumatologic conditions which may have similar presentation.
Pain in CRPS is accompanied by other signs and symptoms such as
- Hypersensitivity of the affected limb
- Swelling, abnormal sweating
- Involved limb may feel unusually cold or warm with or without colour changes
- Nail, skin and hair changes
- Stiffness, weakness, abnormal tone of muscles and jerky movements
The aim in CRPS management is pain control and functional recovery. Early diagnosis and treatment using multi- disciplinary approach is preferred. Your pain management specialist may recommend interventions such as intravenous drug infusions, sympathetic blocks such as stellate ganglion block or lumbar sympathetic blocks and neuromodulation. These are used in combination with medications, physiotherapy and psychology input.
Medications prescribed depend on the phase of disease and the predominant symptoms. A combination of anti inflammatory drugs, neuropathic medications and opioids is commonly utilised. Some other medications including bisphosphonates, free radical scavengers (topical 50% dimethylsulfoxide- DMSO), oral steroids etc. may also be used.
Your physiotherapist will teach you desensitisation techniques if the limb sensitivity is increased. It helps in preventing problems due to weakening and reduced usage of the affected limb. Strengthening exercises are incorporated as the pain is adequately controlled. He may consider specialist interventions such as mirror therapy or graded motor imagery if indicated.
Chronic Post Surgical Pain (CPSP)
Chronic post surgical pain (CPSP) is pain localized to the surgical site or a referred area persisting 3 months after surgery. To diagnose CPSP pain should have been absent before surgery or should have different characteristics from preoperative pain. Other possible causes of the pain such as infection, recurrence of original problem etc need to be excluded.
CPSP is a common complication of surgery and rates up to 80 % in adults have been reported in some studies. CPSP is also reported in children although the incidence is less than in adults. It can have significant consequences for the individual and the World Health Organisation plans to include this as a separate diagnosis in the upcoming version of the International Classification of Diseases, ICD-11.
Type of surgery influences not only the risk of development but also the severity of CPSP. Some surgeries are more prone to develop CPSP such as amputations, thoracotomy, and mastectomy. It is observed after commonly performed operations such as hernia repair, caesarean sections, knee replacement etc. Risk factors for developing CPSP include having pain before surgery, severity of acute pain immediately after surgery, multiple surgeries younger age and site of surgery. Genetic and psychological factors are also thought to play a role. A significant proportion of the cases are attributed to nerve damage.
Management of CPSP required multi-modal approach focussing on
- Patient and family education
- Optimization of medications
- Interventional approaches such as injections and neuromodulation.
- Psychological interventions such as cognitive behavioural therapy