What does pain tell us?

1. Introduction:
My problem-based learning objective for this week is to find out how to differentiate between different types of pain. How are we supposed to do that? My general experience of occupational therapists is that if a patient complains of pain they go and get a doctor or nurse. As occupational therapists are trained in anatomy and physiology it would be great to see occupational therapists investigating pain themselves (at least on a superficial level) before reporting to other multidisciplinary team members. Hence I thought it might be worth sharing my work this week, which is intended for first-year students.

2. History taking:
The first step is taking a history. Medical students are trained to “use the acronym SOCRATES to remember site, onset, character, radiation, associated symptoms, time course, exacerbating factors, and severity”[1]. As a student physiotherapist I was taught to take a history and then use the acronym SIN to remember severity, irritability and nature. What do these things tell us?

2.1. Site: Of course it helps to know where a patient experiences pain. Matching this to your knowledge of pathology may give you an idea of the patient’s condition. In the case of arthritis for example, asymmetrical inflammation is more indicative of osteo-arthritis than rheumatoid arthritis. Pain does not always directly tell us where a problem is though. I personally have had pain in the sacro-iliac region that on examination proved to be a dysfunction of the upper lumbar spine, upper limb pain due to problems with my lower cervical and upper thoracic spine and rib pain that stemmed from my lower thoracic spine. Pain referred from the spine is common but it can happen in other areas too. A soldier once presented to me with intermittent knee pain that on examination turned out to be from a stress fracture in his neck of femur. Due to the potentially misleading nature of pain, it is helpful to understand dermatomes and referred visceral pain. A dermatome is “the cutaneous area supplied by one spinal nerve”[2:p363]. Unfortunately there are huge inconsistencies in the accounts different anatomy texts supply regarding dermatomes[2]. I have therefore only included areas I found consistent in the diagram below.

Figure 1:

Visceral pain is pain from internal organs. It can refer to other body parts. A good example of this is angina referring to the left upper limb. The diagram below has been adapted from my physiotherapy student notes. Unfortunately I have not been able to find any reliable reference for it, so it cannot be relied on as a source.

Figure 2:

2.2. Onset: The nature of onset can give us some indication of the cause of pain. Sudden onset at the time of trauma or gradual onset after trauma can be indicative of injury. If there is a history of trauma, the mechanism of injury can tell us which structures are likely to be injured. Gradual onset with no history of trauma may indicate pathology or occupationally related overuse injury. It is therefore useful to know exactly what the patient was doing when they first noticed the pain, and whether they were doing anything unusual in the previous 24 hours[6]. A good understanding of pathology may be required for this fragment of information to be useful e.g.:

· If a person develops calf pain during a period of bed-rest, after an operation or during a long economy-class flight, this history could lead you to suspect deep vein thrombosis.

2.3. Character: The way patients describe pain may give us an indication of where it comes from.

Table 1: Pain descriptions and related structures[6]

Pain
Structure
Cramping, dull, aching
Muscle
Sharp, shooting
Nerve root
Sharp, lightning-like
Nerve
Burning, pressure-like,
stinging, aching
Sympathetic nerve
Deep, nagging, dull
Bone
Sharp, severe
Fracture
Throbbing, diffuse
Vascular

The list in table 1 is not exhaustive. Pain is a subjective phenomenon so perhaps it will never be possible for one person to understand another’s pain.

2.4. Radiation: Radiation of pain from one body part to another or parasthesia (pins and needles) may suggest nerve involvement[5]. This does not necessarily mean a nerve itself is injured; another damaged structure such as a slipped intervertebral disc or muscle in spasm may be impinging it. Alternatively, radiation may indicate a visceral source such as indicated in figure 2.

2.5. Irritability (exacerbating and alleviating factors): Exacerbating and alleviating factors can be a good indicator of the source of pain, but only if knowledge of anatomy, physiology and pathology are applied to this information e.g.:

· Pain when limbs are elevated that eases when they are kept low, or calf pain that builds up gradually with walking and eases with rest may indicate ischaemia due to atherosclerosis. In the absence of these factors it could be due to injury, infection or thrombosis.
· Chest pain after eating that is worse when leaning forwards or lying down suggests gastric acid reflux or hiatus hernia. In the absence of these factors it could be musculo-skeletal or from other visceral sources (as shown in figure 2).

2.6. Time course: It is useful to know how long a person has had pain, whether it is getting better or worse with time and whether it follows a regular 24-hour pattern e.g.:
· Pain and stiffness first thing in the morning that eases with movement can be an indication of chronic inflammation[6] such as found in osteo-arthritis[7], or oedema, whereas pain that gets worse while a person is at work, or is worse after work but is eased by rest may suggest mechanical, ergonomic or overuse problems, or that a person does not enjoy his or her work.
· Intervertebral discs swell up while people sleep and are gradually compressed while people are active. This can have implications for back pain and nerve root compression.

2.7. Severity: I have heard several accounts of soldiers that were able to continue fighting or running while seriously wounded and on the other end of the spectrum I have met people that cried during drainage of small foot blisters. Occasionally people have presented to me with pain behaviour leading me to believe they were seriously injured, but on examination the actual injuries were relatively minor. The severity of pain can fluctuate according to how much a person is distracted. I therefore believe it would be inhumane to compare one person’s pain to another’s. Regularly asking about severity can give you an idea of whether a person’s pain getting better or worse over time. As a student physiotherapist I was taught to do this with a modified Likert scale: “On a scale of 0-10 where 0 is no pain and 10 is the most excruciating pain a human could ever feel, what number would you give your pain now?” It is worth noting that a person’s perception of number 10 will vary as they experience increasing pain.

Table 2. Putting the subjective assessment together using chest pain as an example[20].

Pain History
Possible source
Superficial, exacerbated
by movement and heavy touch
Muscular
Localised rib pain
exacerbated by inspiration or touch
Rib fracture
Localised to one or
more costochondral joints (occasionally radiating to general chest pain)
Costochondritis
Pain or paraesthesia
in a dermatomal distribution
Neuralgia
Retrosternal, exacerbated
by lying flat or bending forward
Oesophagus
Sharp, stabbing, well
localised pain limiting inspiration. Not exacerbated by touch.
Pleurisy, pulmonary embolism, pericarditis
Severe central chest
pain
Ischaemic heart disease, pericarditis,
pneumothorax, dissecting aortic aneurysm

3. Physical Examination:
3.1. Appearance and feel:[6] Looking at a person may reveal the source of their pain to you. You may for example see swelling, bruising or signs of poor circulation such altered skin colour or missing hair. Even if you cannot see the injury, abnormal posture or movement can give you an indication of the injured structure. If the suspected structures are superficial you can then palpate them to see if they are tender on light or heavy touch. Some body parts are usually tender, so if a person has an injury on one side of his or her body it helps to compare the injured side to the non-injured side. It is also important to check that the pain produced by examination is the same pain the patient is complaining of rather than some other unrelated pain. If pain is reproduced by palpation of the bone, military physiotherapists (in my experience) use tuning forks or ultrasound to vibrate the bone. If vibration reproduces pain they suspect a fracture.

· A parachutist once came to me with groin pain following a heavy landing one month earlier. He was seen by a paramedic and doctor at the scene. At the time his pain was too generalised and vague for them to determine the cause so he was treated with anti-inflammatory medication for groin strain. On examination, active movements and end range passive movements of his hip hurt, but on palpation pain was only reproduced by palpation of the inferior ramus of pubis. I referred him back to the doctor and a bone scan revealed a fracture.

3.2. Passive movements:[6] If you suspect musculoskeletal pain you can distinguish between injuries of muscle and other structures by testing passive movements (when you move the patient’s body parts for them) and static muscle contractions (tensing a muscle without moving). When testing passive movements patients will naturally try to help you by moving actively. If they do so, the movements will feel light. It is essential to make sure the patient is as relaxed as possible and the movements should feel heavy. If passive movements reproduce pain it may be due to stretching a muscle (either at the end of its range or if it is in spasm), nerve, ligament, tendon, joint capsule or skin. Pain at the end of range of movement with a soft end-feel is likely to be due to stretching or compression of soft tissues or joint effusion. Pain at the end of range of movement with a hard end-feel is likely to be due to bone on bone compression. Pain with stiffness through the whole range of movement is likely to be due to joint inflammation or muscle spasm. Pain through range with no stiffness may due to acute joint inflammation or nerve irritation. The characteristics of pain response as previously described can help you determine which structures are affected. Sharp pains tend to indicate new injuries whereas dull aches indicate chronic or healing injuries.

3.3. Static muscle testing:[6] Static muscle contractions do not in theory stress non-contractile structures. If pain is reproduced by tensing a muscle without moving it is likely that the tensed muscle or its tendon is injured. It is worth noting though that muscle contractions will increase joint compression even if a limb is not moving. As bursae sit under tendons, static muscle testing can compress a bursa and give positive signs for bursitis.

3.4. Active movements:[6] If repeated active movements ease an ache, this may suggest chronic inflammation or tissue shortening. If they worsen a sharp pain this is more likely to be acute inflammation.

3.5. Tests that a physiotherapist or doctor may use:

3.5.1. Isolating and stressing individual anatomical structures:[6] Applying anatomical and biomechanical knowledge a doctor or physiotherapist may isolate individual muscles, ligaments or articulating surfaces and apply stress to them to see if they hurt. If a visceral source is suspected a doctor will examine the abdomen. Similarly, physiotherapists and doctors will examine the chest. My current module of study is locomotion so I will not address these now.

3.5.2. Biomechanical assessment:[6] If there is no history of trauma and pain onset was gradual a physiotherapist may look at muscle and bone lengths and joint positions to see whether the painful structures were injured over time due to a mechanical disadvantage.

3.5.3. Nerve pain: If stretching over several joints exacerbates pain, this suggests that unless several structures have been injured the pain may be coming from a nerve. This can be tested by stretching a nerve over several joints consecutively to see if pain increases. A commonly known example of this is the straight leg raise.
· To experience a nerve stretch for yourself lie on your back and raise a straight leg as high as you can until the pulling sensation on the back of your leg stops you. Then keeping your leg still, put your chin on your chest or dorsi-flex your foot. If either of these movements increase the pulling sensation you are experiencing a nerve stretch.
Testing of sensation, muscle power and reflexes can help reveal nerve injuries. Decreased reflexes suggest peripheral nerve injury whereas exaggerated reflexes suggest central neurological impairments.

3.5.4. Circulation: A doctor may palpate pulses to check circulation and lymph nodes to check for infection. Swollen lymph nodes suggest an immune reaction that may be in response to infection.

4. Investigations that doctors may use: Pain that is not affected by movement, weight bearing or structural testing may indicate pathology such a malignancy or infection. If the cause of pain is in doubt following history taking and examination investigations may be undertaken, but these will not be much use unless applied to the full clinical picture.

4.1. Checking medication for side-effects: “Arthralgia is a known side-effect of the following; ACE inhibitors, proton pump inhibitors, quinolones, gonadorelin analogues and tibolones.”[8] http://www.wrongdiagnosis.com/ lists 218 drugs that can cause muscle aches as a side effect. This source may not be accurate, so a doctor may check a patient’s drug history against the side effects listed in the British National Formulary.

4.2. Blood tests: Full blood count (low haemoglobin may indicate chronic disease, elevated white blood cells indicate infection, eosinophilia indicates and allergic reaction)[9]
4.2.1. For inflammatory pathology:[8]
· Plasma viscosity, erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) are used as markers of inflammation (but can be normal in 60-70% of patients with inflammatory pathology).
· Rheumatoid factor (positive in 33% of patients with inflammatory pathology)
· Anti-cyclic citrullinated peptide (anti-CCP) for differential diagnosis between rheumatoid arthritis (positive) and polymyalgia rheumatica (negative).[10]
· Interleukin-6 for polymyalgia rheumatica.
· Serum uric acid (SUA) or plasma urate for gout.[11]
4.2.2. For blood clots: D-dimer[13]which if positive, indicates the presence of an abnormally high level of cross-linked fibrin degradation products due to significant blood clot formation and breakdown somewhere in the body.[18]

4.3. Imaging: Plain x-rays or bone scans may reveal bone pathology or loss of intervertebral disc space. Diagnositc ultrasound, computerised tomography (CT) or Magnetic resonance imaging (MRI) can be used to reveal pathology in other tissues.

4.4. Biopsy or aspiration: Synovial fluid can be analysed for crystals, white blood cell count, blood and fat. Crystals suggest crystalline arthritis, elevated white blood cells suggest inflammatory or septic arthritis and fat or blood may suggest a fracture or tumor.[12] Soft tissue biopsies can be used to check for suspected malignancy or other pathology.

5. When all else fails:
When no cause can be found (such as in fibromyalgia[14]) it is possible that pain is psychosocially mediated, as according to NICE[19:p16] "at least two-thirds of depressed people who see their GP present with physical or somatic symptoms rather than psychological symptoms, making recognition harder." An inflammatory mediator known as substance-P can be released by the central nervous system and peripheral sensory nerves in response to stress[15]. Case study evidence suggests that occupational and lifestyle changes can alter somatic symptoms but this remains to be tested by clinical trials[16].
· When I working as a basic grade occupational therapist in orthopaedics, physiotherapists told me that a patient was unable to move in bed without crying hysterically due to lower limb pain. Medical investigations revealed no pathology, but examination of her social history revealed that she was a refugee with a troubled past, and her husband was being treated with psychotherapy due to their past trauma. Applying the principles from John Eaton’s book on Reverse Therapy[17] the lady was able to transfer independently from bed to commode after two treatment sessions.

6. Summary:
I consulted a general practitioner when writing this blog and he told me that when he was taught medicine, 90% of diagnosis was in history taking. Just by remembering the acronym SOCRATES and looking at active and passive movements, occupational therapists may be able to get a good idea of where pain is coming from before reporting to other multidisciplinary team members. Having said that, if a patient requires prompt analgesia or is likely to need emergency medical or surgical treatment, it may be unethical to delay referral to doctors or nurses in order to take a history.

References:
1. Hayes T (2003) 10 green bottles. http://student.bmj.com/issues/03/04/life/122.php accessed 13:33 31/1/2009
2. Lee M.W.L., McPhee R.W., Stringer M.D. (2008) An Evidence-Based Approach To Human Dermatomes. Clinical Anatomy 21:363–373
3. Snell R.S. (1981) Clinical Anatomy 2nd edition. Little, Brown and Company: Boston.
4. Drake R.L., Vogl W., MitchellA.W.M. (2005) Gray’s Anatomy for Students. Churchill Livingsone: Philadelphia.
5. Saunders D.R., Thompson A.J. (2008) Pain from the digestive organs. http://www.uwgi.org/gut/pain_03.asp accessed 19:58 31/1/2008
6. Magee D.J. (1992) Orthopedic Physical Assessment 2nd edition. W.B. Saunders Company: Philadelphia.
7. Bellamy N., Sothern, J Campbell J., W W Buchanan W.W. (2002) Rhythmic variations in pain, stiffness, and manual dexterity in hand osteoarthritis Annals of the Rheumatic Diseases;61:1075-1080
8. Willacy H. (2008) Aching Joints - Assessment, Investigations and Management in Primary Care. http://www.patient.co.uk/showdoc/40024540/ accessed 19.25 1/2/2009
9. EMIS and PIP (2006) Full Blood Count and Blood Smear. http://www.patient.co.uk/showdoc/27000454/
10. Willacy H. (2007) Polymyalgia rheumatica (PMR). http://www.patient.co.uk/showdoc/40001184/ accessed 20.16 1/2/2009
11. Clinical Knowledge Summaries (2007) Gout - Making a diagnosis. http://www.cks.library.nhs.uk/gout/making_a_diagnosis/diagnosing_gout/hi... accessed 21:20 1/2/2009
12. Siva C, Velazquez C, Mody A, Brasington R. (2003) Diagnosing acute monoarthritis in adults: a practical approach for the family physician. American Family Physician. 68(1) http://www.aafp.org/afp/20030701/83.html accessed 21:33 1/2/2009
13. EMIS and PIP (2006) Deep Vein Thrombosis (DVT). http://www.patient.co.uk/showdoc/23068982/ accessed 10:44 2/2/2009
14. EMIS and PiP (2008) Fibromyalgia. http://www.patient.co.uk/showdoc/27000172/ accessed 12:43 2/2/2009
15. Mailoo V.J. (2006) Psychoneuroimmunology and occupational therapy for inflammatory disorders. International Journal of Therapy and Rehabilitation 13(11): 503-510
16. Various (2005-2007) Testimonials http://www.reverse-therapy.com/Testimonials/default.asp
17. Eaton J. (2006) M.E., Chronic Fatigue Syndrome & Fibromyalgia. The Reverse Therapy Approach. Authors Online: Hertford
18. Lab tests online uk (2007)D-dimer http://www.labtestsonline.org.uk/understanding/analytes/d-dimer/test.html accessed 16:52 29/1/2009
19. NICE (2007) Depression (amended) Management of depression in primary and secondary care: http://www.nice.org.uk/nicemedia/pdf/CG23NICEguidelineamended.pdf accessed 11:39 3/2/2009
20. Parker S., Middleton P.G. (1993) Assessment. In: Webber B.A., Pryor J.A. (eds)Physiotherapy for Respiratory and Cardiac Problems.Churchill Livingstone: Edinburgh. 3-22