Why does my pain seem to spread the longer I have it?

A pattern I see almost every week: a patient describes jaw pain that started in one specific spot — perhaps the right TMJ — and over months or years has slowly spread. Now it includes the temple, the back of the head, the shoulder, sometimes the opposite jaw. They worry that "something else is going wrong". Almost always, the explanation is reassuring and has a clear treatment path: central sensitisation.

What central sensitisation actually is

Central sensitisation is a real, measurable change in how the central nervous system processes pain. The spinal cord and brainstem neurons that handle pain signals become more excitable, more spontaneously active, and respond to a broader range of inputs (Woolf, 2011). Three observable consequences result:

1. Hyperalgesia — the same painful input produces more pain than it used to.
2. Allodynia — non-painful inputs (light touch, mild temperature) start producing pain.
3. Spread — pain is felt in territories beyond the original tissue source, often in the receptive fields of adjacent nerves.

This is not "imagined" pain. It is a change in the wiring of the nervous system that has been demonstrated experimentally in animal models and in human fMRI studies of chronic pain patients (Apkarian et al., 2009).

Why it spreads — the neuroanatomy

The trigeminal nerve (face, jaw, teeth) shares its brainstem processing centre with the upper cervical nerves (neck, scalp, shoulders). This is the trigeminocervical nucleus. When the nucleus becomes sensitised by sustained input from one source — say, the right TMJ — it amplifies signalling for all its inputs. Touch on the temple, the upper neck, even the shoulder can now reach pain-threshold (Olesen, 1991). This is exactly the mechanism behind why TMD pain often spreads to:

• The opposite jaw.
• The temples and forehead (migraine-like patterns).
• The back of the head (sub-occipital and upper cervical regions).
• The shoulder and shoulder blade on the same side.
• The teeth or sinuses (sometimes mistaken for dental or ENT problems).

How clinicians measure it

A specialist physiotherapist can identify central sensitisation through a combination of:

• Distribution mapping — drawing the pain on a body chart. Spread beyond the expected territory of the original structure is the most obvious clinical signal.
• Pressure pain threshold testing — using a pressure algometer to measure the force at which gentle pressure becomes painful. Sensitised patients have lower thresholds, often at sites distant from the original pain.
• Conditioned pain modulation testing — assessing the body's natural "pain dampening" system, which is typically impaired in central sensitisation.
• The Central Sensitisation Inventory — a validated 25-item questionnaire that gives a score from 0–100 (Neblett et al., 2017). Scores ≥40 strongly suggest central sensitisation contribution.

Why early treatment matters

The longer a peripheral pain source goes untreated, the more likely the central nervous system is to amplify and generalise it. A 2018 longitudinal study of TMD patients found that those treated within 3 months of symptom onset had a 78% reduction in 12-month chronification rates compared with patients treated after 12 months (Slade et al., 2018). The window where a localised peripheral problem can be calmed before central sensitisation takes hold is real and measurable.

The good news — sensitisation is reversible

This is the most important sentence in this article. Central sensitisation is a plastic change — it can be reversed, although doing so takes a different approach from simply treating the original tissue. Effective desensitisation programmes share five elements:

1. Address the peripheral driver. If a specific source of nociception still exists (a stuck TMJ, a sensitised neck joint), it needs treating — but with the recognition that this alone will not fix the central side.
2. Pain neuroscience education. Patients who understand sensitisation engage better with the rehabilitation that follows. Wood and Hendrick (2019) showed clinically meaningful effects from education alone.
3. Graded movement and exposure. Gentle, predictable, gradually escalating loading "teaches" the nervous system that movement is safe. Random spikes of pain reinforce the sensitisation; predictable manageable inputs reduce it (Smith et al., 2017).
4. Sleep, stress and mood support. All three modulate central pain processing. Sleep deprivation alone lowers pain thresholds by 15–30% within a week.
5. Time. Plastic changes take weeks to months to reverse, even with optimal treatment. Patients who expect a quick fix often abandon a programme that was working.

What treatment looks like in practice

For a TMD patient with widespread sensitised pain, a typical programme runs 12–16 weeks and combines:

• 4–6 manual therapy sessions targeting the strongest peripheral drivers (TMJ, upper cervical, jaw muscles).
• A structured home programme of graded jaw and neck exercises starting deliberately easy.
• Two or three sessions on pain neuroscience and self-management.
• Active management of sleep and stress.
• Optional CBT input, particularly when anxiety or low mood are part of the picture.
• Where indicated, medication review — some patients benefit from low-dose amitriptyline or duloxetine for centrally-acting modulation.

The takeaway

If your pain has spread over time, you are not "getting worse" in the structural sense — your nervous system has become more efficient at producing pain. This is real, common, and treatable. The right combination of peripheral treatment, pain education, graded movement and time can reverse central sensitisation in the majority of patients. The earlier this is identified and addressed, the more reliably it resolves. If you have been told that your widespread pain is "just chronic" and there is nothing more to do, please consider a second opinion — modern pain science has moved a long way from that view.