Overview
This lecture covers persistent somatic symptoms (PSS) and persistent pain as seen in an orthopaedic setting. It moves from defining PSS and pain, through how pain is classified and processed (including nociplastic pain and the brain’s role in generating pain), to why the standard medical model struggles with these presentations, and finally to a practical approach: validating the patient, using a conceptual model to explain their symptoms, and recognising red flags for relapse or when to seek help.
Persistent Somatic Symptoms (PSS)
- Definition: presence of pain or physical symptoms persisting beyond an expected time for the initiating condition and not fully explained by established biomedical pathophysiology.
- Often triggered by an illness or injury, but the symptoms are out of proportion to what is expected and persist longer than expected.
- Epidemiology: 5-10% of the general population, 20%+ in primary care, even more common in specialist settings, predominantly affects females.
- Previously called “Medically Unexplained Symptoms”, but this term is outdated because good explanations for these symptoms now exist. Understanding the mechanism opens opportunities for treatment.
Common presentations, grouped by system:
- Musculoskeletal: back pain, complex regional pain syndrome (CRPS), fibromyalgia.
- Gynaecology: pelvic pain, sexual dysfunction.
- Gastro-intestinal: non-specific abdominal pain, irritable bowel syndrome (IBS).
- Cardiology: chest pain, shortness of breath, palpitations, POTS (postural orthostatic tachycardia syndrome).
- Neurology: motor (e.g. paralysis/movement disorders - functional neurological disorder, FND), sensory symptoms, non-epileptic seizures.
- General: chronic fatigue syndrome (CFS/ME), long covid, skin disorders.
Pain: Definition, Implications and Classification
IASP (2020) definition: an unpleasant sensory and emotional experience associated with, or resembling that associated with, actual or potential tissue damage.
Important implications of this definition:
- There may not be measurable tissue damage.
- All pain is real and must be respected.
- Emotional and affective factors, including anxiety, guilt, anger, helplessness, fear and depression, may contribute.
- Life experiences, especially prior trauma, may contribute.
- Pain should be thought of in terms of a biopsychosocial model.
- Persisting pain creates behavioural change which may seriously affect function and psychosocial wellbeing.
Classification of pain (slide text corrupted)
The slide text for the classification of pain could not be extracted directly (non-standard font encoding). A low-resolution thumbnail elsewhere in the deck suggests a three-way classification, but this reading is low-confidence and unverified:
- Nociceptive - pain associated with damage to peripheral structures.
- Neuropathic - pain arising from disease or injury to nerves.
- Nociplastic - pain arising from altered functioning of central and peripheral nerve pathways.
Treat this wording as unverified.
Pain may arise at different levels:
- Peripheral stimulus.
- In the conducting pathway.
- In the interpretation of the message.
Pain pathway (diagram as content): a noxious stimulus is detected by nociceptors in the hand (peripheral stimulus), alongside touch detected by mechanoreceptors. Primary afferent neurons (A-delta and C fibres) carry both signals via the dorsal root ganglion into the dorsal horn of the spinal cord. From there the spinothalamic tract carries the signal up to the thalamus, sensory cortex and limbic system. The limbic system and sensory cortex feed into “cognitive activities”, which send a descending pathway back down toward the dorsal horn/ventral horn. Overall, pain processing is a loop: peripheral receptor to spinal cord to brain (interpretation), with a descending modulatory pathway back to the spinal cord.
Nociplastic Pain
Nociplastic pain (2016 concept):
- A pain processing error - a disorder of the nervous system itself.
- Pain is more widespread than expected.
- Pain is more intense than expected.
- May occur in isolation or mixed with nociceptive and/or neuropathic pain.
- Associated with central sensitisation.
- Associated with other CNS symptoms: fatigue, sleep disturbance, memory and mood problems (depression, anxiety).
Nociplastic pain implies involvement of neuroplasticity: the ability of neurological pathways to expand or contract according to their usage. A further implication is that nociplastic pain may be reversible by influencing neurological pathways.
The Brain’s Role in Pain
- The brain receives multiple inputs and messages continually, mostly subconsciously.
- It has to try to create a sensible story from this input (subconscious).
- Based on this, if the brain concludes there is danger to the person, it sends a warning signal to the conscious brain: pain or fatigue.
- Pain then leads to protective behaviours and physiologic responses, e.g. inflammation.
Pain intensity is modified by psychosocial factors:
- Experience.
- Thoughts and beliefs.
- Emotions.
- Stress.
- Context.
In persistent pain, pain intensity is a poor predictor of tissue damage; these psychosocial factors are highly influential instead.
If the brain misinterprets incoming signals because of the prevailing psychosocial environment, the result is:
- Unnecessary pain.
- Unnecessary protective behaviour.
- Persistent pain and inflammation.
Challenges for the Medical Model
The standard medical model runs: Symptoms -> Examination -> Investigations -> Diagnosis -> Treatment. Case examples given: a young woman with paralysis, and a young woman with a sore knee, crutches and brace (CRPS, with visible reddened/discoloured skin over the knee/calf).
Unhelpful approaches to persisting pain in orthopaedics:
- Reassurance alone: “There is no physical cause so you must get better.”
- “There is no physical cause - it must be in your head and you should see a psychiatrist/psychologist.”
Problems these approaches cause:
- Frustration and disappointment for both patient and doctor.
- Anger directed at the doctor.
- A tendency to seek further opinions and fruitless investigations.
- Failure of the medical model to serve either party well.
Broader challenges for clinicians:
- How to explain to a person how and why they have pain when no cause can be found.
- Doctors (and many patients) tend to get stuck in a medical-model way of thinking.
- Developing the confidence, particularly as a junior doctor, to stop further investigation despite fear of missing a diagnosis.
- Avoiding giving the impression that the patient is making up or exaggerating their symptoms.
An Approach to PSS: Using a Conceptual Model
An approach to PSS:
- Normalise and validate the symptoms.
- Show compassion.
- Pain is always pain, whether or not a cause can be found.
- Consider the possibility that the brain has misinterpreted messages, i.e. overestimated the threat.
- Provide a conceptual model to help the person understand how and why they have pain.
- Understanding is everything - it hands back control to the patient, and with control they can potentially heal themselves.
- Analogy used: being lost in the bush.
What makes a good conceptual model:
- Its key purpose is to explain how the brain and nervous system work and how pain sensations occur.
- It should be plausible.
- It does not need to be medically exact.
- It should be simple, using terms that make sense to the patient.
- Conceptualisation offers the opportunity to develop means to eradicate pain by “reprogramming the nerve pathways”.
Integrating Centre diagram (content): a large oval represents the person, divided by a horizontal line into “Conscious” (above) and “Subconscious” (below). At the top, a “Perceived Stimulus, e.g. pain” circle is reached by an upward arrow from an “Integrating Centre” circle sitting on the conscious/subconscious dividing line. Feeding into the Integrating Centre from the subconscious side are four inputs: Prior Experience, Stress, Anxiety, and Social/Spiritual Context. A separate “Physical Change” input, positioned outside/below the oval, also feeds into the Integrating Centre. In sum: the Integrating Centre combines the subconscious/psychosocial inputs (prior experience, stress, anxiety, social/spiritual context) together with physical change (a nociceptive/somatic input) to produce the perceived stimulus (e.g. pain) that reaches consciousness.
Relapse and Red Flags
Factors associated with a positive outcome:
- Early diagnosis.
- Good response to initial treatment.
- Good therapeutic alliance with the clinician.
Factors associated with a poor outcome and relapse:
- Multiple physical symptoms.
- Long-standing symptoms.
- Poor physical functioning.
- Comorbid personality disorder.
- Beliefs that symptoms are irreversible and caused by a disease with a known pathologic basis.
- Illness-related financial benefits.
Red flags - when to ask for help:
- Anxiety.
- Depression.
- Panic.
- Substance misuse in adult patients.
- Secondary gain.
- Excessive doctor shopping.
- No longer attending school or work.
- Relationship with pain becoming obsessive: over-attention or analysis of the pain, or family relationships becoming focused on the pain.
Key Learning Points
- Pain sensations arise from contributions from tissue injury and psychosocial factors.
- Persistent somatic symptoms and nociplastic pain are common.
- Always consider the possible contribution from psychosocial factors in the presentation of an illness or injury.
- Develop a conceptual model to help explain how the brain and nervous system functions.
- Understanding is everything.
Self-test
- Define persistent somatic symptoms (PSS).
- Give the epidemiology of PSS: the rate in the general population, the rate in primary care, and which sex predominantly presents with it.
- List the six body systems in which PSS commonly presents, with one example condition/symptom for each.
- State the IASP (2020) definition of pain.
- List three important implications that follow from the IASP definition of pain.
- Describe the three levels at which pain may arise, and describe the steps of the pain pathway from peripheral stimulus to brain interpretation, including the descending pathway.
- List the features that characterise nociplastic pain.
- Explain what neuroplasticity is, and what it implies for the reversibility of nociplastic pain.
- Describe how the brain generates a pain signal, from subconscious input to conscious warning.
- List the five psychosocial factors that modify pain intensity, and state what this implies about pain intensity as a predictor of tissue damage in persistent pain.
- Predict the three consequences if the brain misinterprets incoming signals due to the prevailing psychosocial environment.
- List the five steps of the medical model flowchart.
- Give the two example statements of unhelpful reassurance/explanation described in the lecture, and list the problems that result from this kind of unhelpful approach.
- List the challenges clinicians face when a patient’s pain has no identifiable structural cause.
- Describe the components of a good approach to a patient with PSS.
- List the three properties a good conceptual model of pain should have for a patient.
- Describe the Integrating Centre diagram: what inputs combine, and what do they produce?
- List three factors associated with a positive outcome and three associated with a poor outcome/relapse in PSS.
- List the red flags that should prompt a clinician to ask for help with a PSS patient.
- A patient presents with a persistently painful, discoloured knee and lower leg after a minor orthopaedic injury, using crutches and a brace, with no clear structural explanation on examination (a CRPS-type picture). Using the concepts from this lecture, describe how you would explain the pain to the patient and structure your approach to management.
Answers
Reveal answers
- PSS is the presence of pain or physical symptoms persisting beyond an expected time for the initiating condition and not fully explained by established biomedical pathophysiology.
- 5-10% in the general population, 20%+ in primary care (even more common in specialist settings), predominantly females.
- Musculoskeletal (e.g. back pain, CRPS, fibromyalgia), gynaecology (e.g. pelvic pain, sexual dysfunction), gastro-intestinal (e.g. IBS, non-specific abdominal pain), cardiology (e.g. chest pain, POTS), neurology (e.g. FND/paralysis, non-epileptic seizures), general (e.g. CFS/ME, long covid, skin disorders).
- An unpleasant sensory and emotional experience associated with, or resembling that associated with, actual or potential tissue damage.
- Any three of: there may not be measurable tissue damage; all pain is real and must be respected; emotional/affective factors (anxiety, guilt, anger, helplessness, fear, depression) may contribute; life experiences, especially prior trauma, may contribute; pain should be viewed via a biopsychosocial model; persisting pain creates behavioural change affecting function and psychosocial wellbeing.
- Pain may arise peripherally, in the conducting pathway, or in the interpretation of the message. Pathway: a noxious stimulus is detected by nociceptors (alongside touch via mechanoreceptors) in the periphery; A-delta and C fibre primary afferents carry the signal via the dorsal root ganglion into the dorsal horn of the spinal cord; the spinothalamic tract carries it up to the thalamus, sensory cortex and limbic system; these feed into “cognitive activities”, which send a descending pathway back down to the dorsal/ventral horn, modulating the spinal signal.
- A pain processing error (disorder of the nervous system); pain more widespread than expected; pain more intense than expected; may occur alone or mixed with nociceptive/neuropathic pain; associated with central sensitisation; associated with other CNS symptoms such as fatigue, sleep disturbance, and memory/mood problems.
- Neuroplasticity is the ability of neurological pathways to expand or contract according to their usage. This implies nociplastic pain may be reversible by influencing (reprogramming) neurological pathways.
- The brain continually receives multiple inputs/messages subconsciously and tries to construct a sensible story from them; if it concludes there is danger to the person, it sends a warning signal to the conscious brain (pain/fatigue), which then leads to protective behaviours and physiologic responses such as inflammation.
- Experience, thoughts and beliefs, emotions, stress, and context. In persistent pain, pain intensity is a poor predictor of tissue damage; these psychosocial factors are highly influential instead.
- Unnecessary pain, unnecessary protective behaviour, and persistent pain and inflammation.
- Symptoms, Examination, Investigations, Diagnosis, Treatment.
- “There is no physical cause so you must get better”, and “there is no physical cause - it must be in your head and you should see a psychiatrist/psychologist.” Problems: frustration and disappointment for both patient and doctor; anger directed at the doctor; a tendency to seek further opinions and fruitless investigations; failure of the medical model to serve either party well.
- Explaining pain when no cause can be found; both doctors and patients tend to get stuck in medical-model thinking; junior doctors need confidence to stop investigating further despite fear of missing a diagnosis; avoiding giving the impression the patient is making up or exaggerating symptoms.
- Normalise and validate the symptoms; show compassion; treat pain as always real whether or not a cause is found; consider that the brain may have overestimated the threat; provide a conceptual model to explain the pain; emphasise that understanding hands back control to the patient (the “lost in the bush” analogy).
- Plausible, does not need to be medically exact, and simple, using terms that make sense to the patient.
- Four subconscious inputs (Prior Experience, Stress, Anxiety, Social/Spiritual Context) plus a Physical Change input combine at the Integrating Centre to produce the Perceived Stimulus (e.g. pain) that reaches consciousness.
- Positive outcome: early diagnosis, good response to initial treatment, good therapeutic alliance with the clinician. Poor outcome/relapse: multiple physical symptoms, long-standing symptoms, poor physical functioning, comorbid personality disorder, beliefs symptoms are irreversible/disease-caused, or illness-related financial benefits (any three).
- Anxiety, depression, panic, substance misuse in adult patients, secondary gain, excessive doctor shopping, no longer attending school or work, and an obsessive relationship with the pain (including family relationships becoming focused on it).
- Normalise and validate the symptoms and show compassion, explaining that pain is always real whether or not a structural cause is found. Consider that the brain may have misinterpreted signals and overestimated the threat, contributing to a nociplastic component alongside any nociceptive input from the original injury. Offer a simple, plausible conceptual model (e.g. the Integrating Centre model, combining prior experience, stress, anxiety and social/spiritual context with the physical change) so the patient understands how and why the pain is occurring, since understanding hands back control and offers a route to “reprogramming” the nerve pathways. Watch for red flags (e.g. anxiety, depression, secondary gain, excessive doctor shopping, an obsessive relationship with the pain) that would prompt seeking further help, and note factors that favour a good outcome such as early diagnosis and a good therapeutic alliance.