What is central sensitisation and how is it addressed clinically?

What is central sensitisation: clinical definition and neurobiological basis?

Clinical definition

The central awareness is a state of hyperexcitability of the central nervous system in which neurons involved in nociception respond in an increased manner to normal or even subthreshold stimuli. Clinically, pain is observed which may be disproportionate to tissue damage, expansion of receptive fields and characteristic sensory phenomena:

• Alodyniapain to usually non-painful stimuli (e.g. light touch).
• Hyperalgesiaincreased pain response to noxious stimuli.
• Temporary pain summation (wind-up)pain: progressive increase in pain with repeated stimuli of equal intensity.
• Persistence of the painful sensation after cessation of the stimulus (after-effect).

Neurobiological basis

It is underpinned by mechanisms of synaptic plasticity similar to a long-term potentiation in the medullary dorsal horn and trigeminal nuclei, with activation of NMDA receptors, They also help to reduce the number of nociceptive pathways, phosphorylate ion channels and increase the synaptic efficacy of nociceptive pathways. Contribute to the reduction of GABAergic/glycinergic inhibition, the imbalance of the top-down control (decreased inhibition and increased facilitation from the brainstem), and processes of neuroinflammation with activation of microglia and astrocytes that release pronociceptive mediators. Functional changes in cortical pain networks that modulate sensory gain and processing of nociceptive signals have also been described.

Common symptoms and manifestations of central sensitisation in persons with persistent pain

Central sensitisation is associated with a amplification of nociceptive signals in the nervous system. In people with persistent pain, this can result in a pain response disproportionate to the stimulus, pain spread to uninjured areas, and daily fluctuations with no clear single trigger.

• Hyperalgesiapain: increased intensity of pain in response to stimuli that would normally be painful.
• Alodyniapain: pain to non-painful stimuli, such as rubbing of clothing or light pressure.
• Generalised or migratory paindistribution: wide, shifting and often bilateral distribution, not limited to a specific nerve territory.
• Sensory hypersensitivitydiscomfort or worsening of pain with intense light, noise, odour, temperature or vibration.
• Temporary submersion and residual painpain: progressive increase in pain with repeated stimuli and persistence of pain after cessation of the stimulus.
• Paresthesias and dysesthesiastingling, burning or “burning” sensation with no obvious peripheral cause.
• Sleep disturbancessleep and frequent awakenings, which are often associated with increased sensitivity the next day.
• Fatigue and cognitive fogmarked tiredness, mental sluggishness and difficulty in concentrating or remembering recent information.

These manifestations can be intensified by stress, The pain intensity is often not clearly related to peripheral findings. Pain intensity is often not clearly related to peripheral findings. Coexistence of functional symptoms such as tension or migraine headache, temporomandibular pain, pelvic or abdominal discomfort and urinary urgency is common, without implying a single causal mechanism. The presence and combination of these symptoms varies between individuals and, by themselves, do not establish a specific diagnosis.

How central sensitisation is diagnosed: clinical assessment, complementary tests and differential diagnosis

Clinical assessment

The clinical diagnosis part of a guided interview and a physical examination aimed at identifying an amplified and generalised pain pattern. Pain disproportionate to tissue findings may be observed, allodynia (pain in response to non-noxious stimuli), hyperalgesia, The diagnosis is supported by the temporal summation of pain (increased pain with repeated stimuli) and diffuse sensitivity to pressure. Temporal summation of pain (increased pain with repeated stimuli) and diffuse pressure sensitivity support the diagnosis. Validated questionnaires, such as the Central Sensitisation Inventory (CSI), can provide complementary information, but do not in themselves constitute diagnostic confirmation.

Complementary tests

There is no complementary test or specific biomarker. Tests are used to rule out alternative causes and, when available, to detect alterations in pain processing: quantitative sensory assessment (thermal and pressure thresholds), measurement of temporal summation and conditioned pain modulation, or algometry. Basic blood tests and imaging studies are requested according to clinical signs to exclude inflammatory, autoimmune, endocrine or structural pathology. Advanced neuroimaging or neurophysiology techniques are of research interest and are not routinely used in clinical practice.

Differential diagnosis

• Nociceptive pain mechanical or inflammatory: localised tissue lesions (osteoarthritis, tendinopathies, stress fractures, arthritis) with anatomical correlation and inflammatory signs where appropriate.
• Neuropathic painsomatosensory system lesion/disease (radiculopathy, peripheral neuropathy) with neurological distribution, objectifiable sensory disturbances and, where appropriate, compatible electrophysiological studies.
• Systemic disordersRheumatological diseases, hypothyroidism, anaemia or vitamin deficiencies, which may be associated with generalised pain and fatigue.
• Sleep factors and mental healthinsomnia, sleep apnoea, depression or anxiety can modulate the perception of pain and should be assessed without exclusively attributing pain to them.
• Pharmacological effects and other causes: hyperalgesia induced by opioids or other drugs associated with myalgia.
• Clinical overlaps with chronic pain syndromes (e.g. fibromyalgia), applying specific criteria where appropriate.

Clinical approach to central sensitisation: multimodal approach and prudent therapeutic options

The comprehensive assessment prioritises the identification of clinical patterns compatible with central sensitisation: generalised or disproportionate pain, hypersensitivity (hyperalgesia, allodynia), fatigue, sleep disturbances and cognitive difficulties. The presence of triggers, comorbidities (e.g. headache, mood disorders, irritable bowel syndrome) and psychosocial factors that may modulate the painful experience are assessed. Physical examination is aimed at differentiating active nociceptive/neuropathic generators, ruling out “red flags” and estimating movement and load tolerance. Realistic functional goals are proposed and a multimodal approach with shared decision-making and regular monitoring.

Combined and progressive non-pharmacological interventions are at the core of management. The pain education helps to reinterpret symptoms and align expectations. The graduated exercise (low to moderate intensity aerobic, strength and mobility with progressive exposure) aims to improve capacity without exacerbating flare-ups; pacing and self-regulation of effort are key. The psychological therapy with validated approaches (e.g. cognitive-behavioural or acceptance and commitment) can support coping, reduction of catastrophising and stress management. Routines are recommended for sleep hygiene, The programme also includes relaxation and breathing techniques, and adjustments to habits that minimise the physiological burden.

The prudent pharmacotherapy is considered when symptoms persist despite non-pharmacological measures or to treat relevant comorbidities. In selected cases, low-dose tricyclic antidepressants, serotonin-norepinephrine reuptake inhibitors or gabapentinoids may be considered after an individual assessment of benefit-risk balance, interactions and preferences; it is suggested to start with low doses, reassess efficacy and adverse effects and deprescribe if they are of no clinical value. Prolonged use of opioids is usually avoided due to their risk profile, and invasive interventions are not considered first-line. Regular monitoring with functional metrics, flare recording and stepwise adjustments supports safety and consistency of the treatment plan.

Disorders in which central sensitisation may be present: fibromyalgia, migraine, irritable bowel syndrome and other conditions.

The central awareness describes a state of hyperexcitability of the central nervous system with amplified sensory processing, which can manifest itself as hyperalgesia (increased pain), allodynia (pain to non-painful stimuli) and sensitivity to light, noise or temperature. There is no single diagnostic test; its presence is inferred by the clinical pattern and, when available, by measures of sensitivity.

Disorders in which it is usually considered

• Fibromyalgia: widespread musculoskeletal pain, fatigue, sleep disturbances and reduced pain thresholds consistent with central pain amplification.
• Migraine: episodes with photophobia, phonophobia and cutaneous allodynia; in some patients central phenomena are described that facilitate persistence and chronification.
• Irritable bowel syndrome: recurrent abdominal pain and increased visceral tenderness without demonstrable structural lesion, with possible central pain modulation.

Other conditions in which it may be present

• Temporomandibular disorders and chronic orofacial pain.
• Chronic tension headache and medication-overuse headache.
• Chronic non-specific low back pain and chronic neck pain/chronic whiplash.
• Chronic pelvic pain syndrome, dyspareunia and vulvodynia.
• Painful bladder syndrome/interstitial cystitis.
• Complex regional pain syndrome and persistent musculoskeletal pain without proportional active tissue damage.

The contribution of central awareness is heterogeneous and varies between individuals and over time. Its identification is clinical and should be integrated with the assessment of mechanisms nociceptives, inflammatory y neuropathic, avoiding single attributions when there are treatable peripheral causes.