fbpx

Central Pain Syndrome

Central Pain Syndrome

What is Central Pain Syndrome?

L. Edinger, a German neurologist, was the first to describe central pain in 1891. For years, it was thought that the majority of cases of central pain syndrome were caused by thalamic injury, which was most commonly caused by a stroke. After two French neurologists identified the so-called thalamic condition (1906), which had a pain component, the disorder was later dubbed Dejerine-Roussy syndrome. Central pain became synonymous with thalamic pain syndrome after that, and until recently. Damage to the pain-conducting circuits anywhere along the neural axis, from the spinal cord to the sensory cortex, can produce central pain syndrome, according to researchers. This includes cases following injury or a stroke. As a result, the current nomenclature for this collection of illnesses is a central pain syndrome, which recognises that central pain can be caused by damage to multiple parts of the CNS (not just the thalamus) and that a stroke is not always the primary cause. Central pain syndrome is divided into two types: pain that originates in the brain or brainstem, and pain that originates in the spinal cord. Central post-stroke pain is the name for a kind of central pain syndrome produced by CNS damage caused by a stroke. Pains characterised as central in disorders like Parkinson’s disease are not actually central pain and have different pathophysiology and therapy than true central pain; these are known as central-pain allied conditions.

Several million people are said to be affected by central pain syndrome around the world. Central pain affects about 5-10% of people who have a stroke, 20-40% of those who have had a spinal cord injury, nearly 30% of people with multiple sclerosis, and an unknown number of people with additional diseases.

Signs & Symptoms

Central pain syndrome can appear days, weeks, months, or even more than a year following a central nervous system injury. The disorder can, however, arise shortly after an accident or within a day. Central pain syndrome is almost always a lifelong condition.

Central pain syndrome can affect only a small section of the body, such as the hands or feet, or it can affect the entire body. Some parts of the body may be impacted more severely than others. Touch, emotions such as stress, certain movements or general level of activity, and temperature variations, particularly cold temperatures, can all alter pain throughout the day. Symptoms may be alleviated by rest and distraction.

Central pain syndrome can be very different from person to person, depending on the underlying aetiology of the disorder. Central pain syndrome symptoms might be vague and difficult to define in some circumstances. Burning, stabbing, lacerating, pressing, aching, prickling, or tingling (a feeling of being on pins and needles) are all possible pain sensations. In many cases, the most apparent symptom is a persistent burning feeling. Pain can be persistent and unrelenting, or it can be sporadic (intermittent). The discomfort is frequently persistent and moderate to severe in severity. Pain has been described as terrible in some circumstances. Some people who are impacted may experience severe, terrible pain in short bursts, similar to the sensation that happens when a dental probe touches an exposed nerve. The persistent discomfort associated with central pain syndrome can be devastating in some situations, affecting an individual’s ability to do daily duties and lowering their quality of life dramatically.

The pain sensations associated with central pain syndrome are usually spontaneous, meaning they happen without a known cause or trigger. People with this illness may be hypersensitive to acute painful stimuli or have a heightened response to them (hyperalgesia, hyperpathia), which implies that pain that would ordinarily be minor or insignificant is felt to a much larger extent. Furthermore, individuals may experience pain from stimuli that are ordinarily not uncomfortable (allodynia). Affected persons, for example, may suffer discomfort even when barely touched. A strong breeze, the weight of a blanket, or even the clothes a person is wearing can all produce agony in extreme situations.

Some people with central pain syndrome may feel sensory impairment or distortion at first, particularly with touch (dysesthesia). A hazy, unpleasant sensation is described as dysesthesia. Some people may have agonising numbness, particularly in their feet. Individuals with central pain syndrome have also reported itching (pruritus).

Other noticeable, associated symptoms include lack of sensation (hemihypesthesia), partial or total muscle paralysis (hemiparesis, hemiplegia), and, on occasion, strange, involuntary, irregular jerky motions and sluggish, writhing movements in those with central post-stroke discomfort (hemichoreoathetosis).

Diagnosis

Identification of distinctive symptoms, a complete patient history, a thorough clinical evaluation, and a variety of specialist testing are used to diagnose central pain syndrome. Individuals who report pain or other odd feelings after a central nervous system injury may have central pain syndrome. Before a diagnosis of central pain syndrome can be made, other causes of pain may need to be ruled out.

Clinical Testing and Workup

Tumours, infarcts, cerebral haemorrhage, demyelinating plaques, and other causative lesions are best visualised with magnetic resonance imaging (MRI). An MRI creates cross-sectional images of certain organs and body tissues using a magnetic field and radio waves. Recent variations of this method (such as magnetic resonance spectroscopy or default-state MRI) have sparked only academic curiosity.

Laser evoked potentials are rarely required to confirm pain conducting route impairment and are not routinely available.

Screening techniques (in the form of questionnaires) have been developed, but they miss 12-45% of cases and are thus not advised for confirming a diagnosis.

Causes

Damage to the central nervous system — the brain, brainstem, or spinal cord – causes the illness. A stroke, multiple sclerosis, spinal cord (but also brain) injury, or brain tumours are all common causes of such damage. Central pain syndrome can also emerge following brain or spine neurosurgery treatments.

Damage to the pain-transmission system from the spinal cord up to the cortex, the grey matter that covers the cerebral hemispheres, causes central pain syndrome.

A disruption in communication between the sensory thalamus and the sensory brain causes central pain syndrome. The thalamus is a deep brain region that works in tandem with the cortex to act as a major hub in sensory processing. The cortex and some thalamic nuclei are “locked” together in an altered state of activity when this synchronisation is disrupted by a neurological injury that unbalances the brain’s inhibitory tone. CPS is caused by a faulty corticothalamic loop along the sensory pain transmission pathways.

This knowledge points to the development of novel experimental therapy techniques (see below).

Treatment

Standard Therapies

Treatment for central pain syndrome is ineffective because, while most patients experience some alleviation, total control is rare. Furthermore, medicines that have been shown to be effective in some people may not be effective in others.

Traditional pain relievers (e.g., NSAIDs) provide little to no help for people suffering from central pain syndrome. However, for the majority of those affected, pharmacological therapy remains the first line of treatment. Amitriptyline and lamotrigine, two medications, have been shown to help people with central pain in the brain in controlled trials. Amitriptyline is a mood stabiliser. Lamotrigine is a seizure medication (anticonvulsant). Antiarrhythmics like mexiletine and topical anaesthetics like lidocaine can help.

Although MHRA-approved for central pain, gabapentinoids, another type of anti-seizure medication, are not recommended as first-line therapy for central pain: a thorough, conflict-free review of the entire database (including unpublished studies) reveals that these drugs are ineffective in the vast majority of patients, with meaningful benefit occurring only infrequently. Despite being licenced by the MHRA for chronic pain, unbiased analysis of the complete database reveals that ziconotide has a relatively low therapeutic index, with the majority of patients experiencing no consistent effect. Opioids like morphine and levorphanol are ineffective in the vast majority of situations and are actually contraindicated in the vast majority of people.

The effectiveness of medication therapy is reduced in certain circumstances due to side effects.

Recent advancements point to the addition of alternative/complementary therapies to pharmacological therapy. Virtual-reality-assisted hypnotherapy is of particular interest. Also recommended are supportive care, rehabilitation, and counselling.

 

Investigational Therapies

Extradural cortical stimulation of the sensory-motor region (MCS/PCS) is a treatment that has been used to treat refractory, chronic pain in people with central pain of brain origin who do not respond to medication therapy. To give electrical stimulation, a stimulating paddle or plate is inserted extradural (or sometimes subdurally) on the primary motor cortex and/or primary sensory cortex. The paddle is inserted extradural on the dura mater, the outermost layer of the membranes that line the brain and spinal cord (meninges). The paddle is inserted through two burr holes or by removing a little section of the skull temporarily (craniotomy).

According to medical research, more than half of people saw a pain reduction of more than 50% with no notable side effects. This type of stimulation is more effective than placebo stimulation, according to studies.

Although noninvasive forms of cortical stimulation, such as transcranial magnetic stimulation (TMS) or transcranial direct current stimulation (tDCS), have been used to treat CPS, results reveal that their efficacy falls short of that of neurosurgical intervention. They may, however, aid in the selection of patients for surgical implantation.

With a few exceptions and only after a trial of CS, much research has shown that deep brain stimulation is NOT recommended for the treatment of persons with central pain syndrome. An electrode is implanted in the thalamus, and a thin wire is inserted beneath the skin and attached to a small battery pack during the process (which is also placed underneath the skin). Lethal brain bleeding is a modest but actual risk.

Spinal cord stimulation helped a small percentage of patients with both CCP and BCP in resource-constrained settings, although long-term control is unusual. Some people get pain relief by injecting medications directly into the cerebrospinal fluid that surrounds the brain and spinal cord (intrathecal administration). This has been done using drugs like baclofen and midazolam. A few people have reported pain relief after having a morphine pump implanted that distributes medicines intravenously, but this should only be used as a last resort. Individuals with central pain syndrome do not always respond well to intrathecal medication administration. In this area, however, much more research is required.

Individuals with central pain syndrome have previously been treated with surgery. This involves invasive, severe procedures including surgically removing or destroying specific portions of the brain, such as the thalamus (thalamotomy) and the mesencephalon (mesencephalotomy) (mesencephalotomy). However, the majority of these procedures were linked to low long-term success rates as well as a high risk of complications and morbidity. Individuals with central pain syndrome no longer require such invasive operations.

A surgical treatment known as subparietal leucotomy/capsulotomy, according to medical literature, has the ability to remove the discomfort associated with central pain syndrome. A tiny lesion is produced in certain parts of the white matter of the brain to interrupt the descending arm of the corticothalamic loop during this surgery. This technique reduced pain in the affected person instantly and totally in one case described in the medical literature. More research is needed, however, to determine the procedure’s long-term safety and usefulness as a viable therapy for those with central pain syndrome.

Recent discoveries in the field of spinal cord injury show that, where possible, removing an injured portion of the spinal cord together with a vertebrectomy or several discectomies may help both motor and sensory rehabilitation. This is an experimental path that will be tested in humans.

 

Outook

Central pain syndrome is a neurological condition caused by impairment of the central nervous system’s sensory pathways (CNS). Pain (but sometimes pruritus) and loss of sensation, commonly in the face, arms, and/or legs, are common complaints. Pain can be mild, moderate, or severe in severity and is frequently consistent (although can sometimes be intermittent). Individuals who are affected may become hypersensitive to painful stimuli. The sort of pain that individual experiences might vary depending on the underlying cause of the condition and the location of the central nervous system that is afflicted. Central pain syndrome has the ability to disturb a person’s daily life. In severe situations, the pain can be excruciating and unrelenting, affecting a person’s quality of life significantly. A variety of disorders can cause central pain syndrome, including stroke, multiple sclerosis, spinal cord injury, brain tumours, and iatrogenic central nervous system damage.

SCROLL DOWN FOR THE NEXT ARTICLE
NEXT ARTICLE