What is chronic pain?
Chronic pain affects many people, across a variety of patient populations. Acute pain indicates a short duration and/or recent onset event, thought to be a protective mechanism of the body. Normally, this leads to healing and restoration however, persistent pain that lasts for over 12 weeks is referred to as chronic pain. This is considered pathological and is categorised as a condition in its own right. In such cases, the pain signals travelling between the spinal cord and the brain become over-activated. While pain mechanisms are complex and we do not yet understand the depth of this topic, it is likely that pains syndromes result from dysfunctional pain signalling. This information is transmitted to the central nervous system (the brain and the spinal cord) as a hyper-sensitive signal and thus, is perceived as abnormally painful.
In this blog we will focus on chronic neuropathic pain (pain relating to nerves), and we’ll also look at complex regional pain syndrome.
What are the signs of chronic pain syndromes?
So we know that about 30% of all nerve pain is due to diabetic neuropathy; this is caused by persistently raised blood sugar levels which damage the peripheral nerves of the body, particularly the finer, more delicate structure that infiltrate your hands and feet. Neuropathic pain may also result from trauma to nerve tissue, alcoholism, viral infections like shingles, and many neurological conditions like multiple sclerosis or stroke.
Neuropathic pain presents in various, often overlapping ways:
Spontaneous pain is pain that appears to occur without a physical stimulus. Patients describe it as shooting or sharp pain, or a numbing pain that feels like ‘pins and needles’.
Allodynia or ‘evoked pain’ is caused by a stimulus or experience that is not usually painful. For example, trigeminal neuralgia can cause severe facial pain from the lightest of touches to the face, as compression of the trigeminal nerve magnifies the pain response. Patients have said this can feel like a ‘bolt of lightning’ striking their face.
Hypoalgesia is when the sensation of pain is reduced, as the stimuli along the neural pathway is either decreased or interrupted. This is how analgesic drugs (like paracetamol) work to reduce pain. Patients affected by hypoalgesia may present with underlying conditions such as diabetic neuropathy, hereditary neuropathy, or hypertension as damaged nerves become less effective in transmitting pain messages.
Dysesthesia is caused by nerve damage, which causes nerves to misfire and send confusing messages to the brain when interpreting various sensations, like touch, or warmth. The brain responds by sending out pain signals in an attempt to resolve the confusing message; itchy, burning or sharp pain results from this. Dysesthesia is often rooted in carpal tunnel syndrome or multiple sclerosis, although it can also result from any kind of nerve damage.
Central post-stroke pain (CPSP) affects up to 20% of stroke survivors. A stroke can damage an area of the brain associated with pain perception. This means that pain stimuli may be interpreted abnormally and can lead to different types of pain sensation: burning or tingling, or perhaps a shooting or numbing pain on the stroke-affected side of the body (usually opposite to the affected side of the brain).
What about complex regional pain syndrome?
Complex regional pain syndrome (CRPS) usually develops within a month after an injury or surgery. Patients often report inflammation, and severe burning or shooting pain. However, its aetiology (cause) remains unclear. One leading theory suggests that normal recovery is complicated by CRPS, as the body reacts more severely than usual to physical trauma. The nervous, immune, and circulatory systems are all believed to ‘malfunction’ in response. This affects communication between the brain and the limbs; cementing the neuropathic symptoms of agonising pain and oversensitivity. Patients have reported ‘flare ups’ during times of stress in particular.
How do we manage symptoms?
Chronic pain commonly requires a multidisciplinary effort. Neurologists, specialist pain teams, physiotherapists, and psychotherapists could all be involved in a patient’s care.
Pain relief
Pharmacology such as anti-seizure drugs or anti-depressants can help patients with nerve damage. Tricyclic antidepressants have proven effective in relieving diabetic neuropathic pain. Alternatively, some patients find relief with a TENS (transcutaneous electric nerve stimulation) machine. It appears this works by electrical stimulation of nerve fibres which block the signals of pain impulses – it acts as a pain “distraction”, thus, decreasing the severity of the perceived pain.
Physiotherapy
Supporting patients to improve their mobility and function can alleviate chronic pain. This often supports the patient’s emotional and/or psychological wellbeing, which aids to better healing and an improved quality of life.
Holistic
Patients should be given varied, patient-centred support as long term pain can become clinically worse if not dealt with effectively. Commonly, psychotherapy and occupational therapy can both support recovery.
How could neurosurgeons treat chronic pain?
We can treat trigeminal neuralgia with nerve decompression. Microsurgery is used to relieve the compression which may decrease pain sensitivity and therefore reduce symptoms. Alternatively, a glycerol rhizotomy may be considered. In this procedure, glycerol is injected into a branching of the trigeminal nerve; this aims to stunt pain transmission signals to the brain.
Neurostimulation, such as spinal cord stimulation may be used to block pain signals travelling up to the brain by implanting a low-voltage electrical current. We safely secure the implant into the epidural space, found between the spinal cord and the vertebrae. Patients are given a remote control to take home, which allows them to switch the current on when in pain. Neurostimulation has been shown to be effective in treating chronic sciatica and spinal cord injury.
A cingulotomy is a surgical intervention we can use if other methods of pain management have not worked. The surgeon delicately uses laser or thermal technology to create lesions in the anterior cingulate cortex; a part of the limbic area of the brain that processes feelings, emotions and chronic pain. Patients with spinal cord injury and cancer pain report the best outcomes from this procedure.
Final thoughts?
So we’ve learnt that chronic pain can present in myriad ways and that it’s often a complex, multidisciplinary journey for patients. Neuropathic pain can have a poor prognosis, yet we are coming up with more and more ways to improve quality of life. Positively, we continue to learn more about the mind-body connection; which can empower all those with long term health conditions, not just chronic pain sufferers. Learning together with patients and making their health not just holistic, but also a shared, community experience, is something we can all work towards.
References
https://www.nhsinform.scot/illnesses-and-conditions/brain-nerves-and-spinal-cord/chronic-pain
https://painconcern.org.uk/resources/about-pain/
https://bestpractice.bmj.com/topics/en-gb/694
https://bnf.nice.org.uk/treatment-summary/pain-chronic.html
https://en.wikipedia.org/wiki/Hypoalgesia
https://www.stroke.org.uk/sites/default/files/user_profile/pain_after_stroke.pdf
https://www.aans.org/en/Patients/Neurosurgical-Conditions-and-Treatments/Chronic-Pain
https://www.columbianeurosurgery.org/treatments/cingulotomy/
https://painconcern.org.uk/complex-regional-pain-syndrome/
Credits
Sidi
Brainbook Editorial Officer
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