Chronic pain Flashcards
Which one of the following terms is correctly matched with its definition?
a. Allodynia: an unpleasant abnormal sensation, whether spontaneous or evoked
b. Dysaesthesia: increased sensitivity to stimulation, excluding the special senses
c. Hyperaesthesia: pain due to a stimulus which does not normally provoke pain
d. Hyperalgesia: an increased response to a stimulus which is normally painful
D
Which of the following pain rating scales includes psychological assessment of the patient?
a. Brief Pain Inventory
b. Short Form – 36 Physical Function Scale
c. Galer Neuropathic Pain Score d. McGill Pain Questionnaire
D
Which of the following mechanisms is involved in central sensitisation? a. Increased sensitivity of nociceptor
b. Sympathetically mediated crosstalk
c. Wind-up phenomena
d. Spontaneous neuronal activity
C
Hyperalgesia is defined as ‘an increased sensitivity to pain’, which may be caused by damage to nociceptors or peripheral nerves. Primary hyperalgesia describes pain sensitivity that occurs directly in the damaged tissues. This occurs by peripheral sensitisation whereby
nociceptors exhibit reduction in threshold and an increase in responsiveness.
Secondary hyperalgesia describes pain sensitivity that occurs in surrounding or distant undamaged tissues. This is a result of central sensitisation wherein there is an increase in the excitability of neurons within the central nervous system, so that normal inputs begin to produce abnormal responses.
Regarding the transition of acute to chronic pain, which of the following statements is true?
a. Persistent C-fibre activation causes wind-up or central sensitisation
b. Ion channel changes in neuromas following nerve injury
c. Phenotypic switching of Aβ fibres occurs d. All of the above
D Glutamate receptors (AMPA and NMDA) have been identified in spinal cord. Activation of these receptors by nociceptive inputs from periphery is involved in development of chronic pain. Hence, NMDA antagonists such as ketamine are used to treat certain chronic pain states. Persistent nociceptive stimulation of C fibres produces hyperalgesia and allodynia through wind-up phenomena and central sensitisation. Axonal sprouting and neuroma formation subsequent to nerve injury exhibit altered up- regulation of sodium channels, and down-regulation of potassium channels. The net result is increased neuronal excitability. Lastly, sensory Aβ
undergo phenotypic switching to C fibres and start conducting pain.
Regarding low-back pain, which of the following is correct?
a. Mechanical back pain is not common
b. Lumbar X-ray should always be taken to rule out serious pathology c. Pain at night is a ‘red flag’ and should be evaluated further
d. Most are advised a 2-week bed rest
C Low-back pain is pain in the lumbosacral region arising from the spinal or paraspinal structures. Sciatica (radicular leg pain) may accompany low- back pain but is regarded as a separate entity. About 50%–80% of adults experience low-back pain. Most backaches (85%–90%) are simple low-back pain (mechanical back pain) in which no particular pathology exists. Non- mechanical backaches may be due to more serious conditions like cancer, infection or inflammatory arthritis. Visceral pathologies may also lead to low- back pain.
‘Red flag’ signs: non-mechanical pain, thoracic pain, history of cancer, HIV, weight loss, structural deformity, young (< 20 years) or old
(> 55 years), recent trauma, osteoporosis, night pain and bladder/bowel dysfunction.
Imaging: should be done only if the history or clinical examination is suggestive of non-mechanical back pain.
Management: mostly early mobilisation and pain relief. Physiotherapy may be needed if progress is slow. A minority will need further evaluation and management.
Note: bed rest is not effective and may be harmful.
Which of the following statements regarding spinal disc prolapse is incorrect?
a. It is most common at L5–S1 level
b. Severe pain means nerve root compression
c. Most herniations are posterolateral
d. Intradiscal pressures are highest while sitting and bending forward
B A spinal disc herniation is a condition affecting the spine due to tear in the outer, fibrous ring (annulus fibrosus) of an intervertebral disc allowing nucleus pulposus to bulge out beyond the damaged outer rings. Tears are almost always posterolateral in nature owing to the presence of the posterior longitudinal ligament. This tear causes release of inflammatory chemical mediators which may directly cause severe pain, even in the absence of nerve root compression. They most often result due to wear and tear, and occur most frequently at L4–L5 or L5–S1 levels. The second most common site is lower cervical (C5–C6 or C6–C7), while it is uncommon at thoracic levels. The sitting and bending forward position (associated with desk jobs) cause the highest increases in intradiscal pressures predisposing to prolapse.
Which of the following is not a feature of L5–S1 disc prolapse (causing significant compression on the corresponding nerve roots)?
a. Inability to walk on toes
b. Inability to walk on heels
c. Loss of ankle reflex
d. Reduced sensation on lateral plantar foot surface
B
Which of the following is not a feature of C5–C6 disc prolapse (causing significant compression on the corresponding nerve roots)?
a. Inability to flex the elbow
b. Inability to extend the wrist
c. Inability to flex the wrist
d. Anaesthesia over index finger
C
Regarding lumbar facet arthropathy, which of the following is false? a. Facet joints are innervated by the medial branches of dorsal rami
b. Radiation of pain below the knee is uncommon
c. A proper history and clinical examination reliably establishes diagnosis d. Diagnostic blocks employ only local anaesthetics
C Facet arthropathy causes 15%–40% of cases of low-back pain due to dysfunction or inflammation of the facet (zygapophyseal) joints. These joints are formed by the articulation of the articular processes of the adjacent vertebrae. They are innervated by two medial branches of the dorsal rami
of the corresponding spinal nerves.
The patient complains of deep, achy, non-specific low-back pain localised over the affected facet joint. Radiation to the thigh is possible, but radiation distal to the knee is uncommon. The pain is worse with lumbar extension, extensive walking or sitting for long periods of time. The bowel and bladder are not involved. On examination, there is pain with deep palpation over the affected facet joint. Paraspinal muscle spasm, loss of lumbar lordosis and limited extension of spine may be noted.
However, historic or physical examination findings cannot reliably diagnose lumbar zygapophyesal joint pain. The most accepted method for diagnosing pain arising from the lumbar facet joints is with low-volume intra-articular injections or medial branch blocks. Diagnostic blocks use
only local anaesthetics, and analgesics (opioids) for sedation must be avoided.
Regarding lumbar canal stenosis, which of the following statements is correct?
a. Neurogenic claudication occurs immediately after starting to walk
b. There is an increase in pain after spine flexion
c. Walking uphill is easier than walking on a flat surface d. Causes inability to ride a cycle
C Lumbar spinal stenosis is the narrowing of the spinal canal (transforaminal canal), resulting in nerve compression of the spinal roots laterally. It usually affects middle-age patients (> 55 years). Symptoms include leg pain, weakness, paraesthesia and radicular pain of the involved spinal root. This is similar to vascular claudication, but different in many respects, hence it is called pseudoclaudication or neurogenic claudication.
Patients with mild to moderate symptoms are treated conservatively, while those with severe symptoms may need surgery (laminectomy) if conservative treatment fails by 3–6 months. In fact, lumbar spinal stenosis has become the
most common indication for lumbar spine surgery.
Regarding sacroiliac joint pain, which of the following is true? a. It is worse toward the end of the day
b. Standing on the involved joint relieves the pain
c. Lasègue’s test is positive
d. Intra-articular injections are an effective form of treatment
D
The sacroiliac joint (SIJ) is innervated posteriorly by lateral branches of the dorsal primary rami of L4–S3 and anteriorly by lateral branches of the dorsal primary rami of L2–S2. SIJ pain accounts for 16%–30% of cases of chronic mechanical low-back pain.
SIJ pain mainly involves the buttocks, although it may be referred to the thigh, abdomen, groin or legs. It may also occur with systemic conditions such as ankylosing spondylitis, Crohn’s disease and gout. SIJ pain is worse in the morning and can be exacerbated by spine flexion, prolonged sitting and weight bearing on the painful limb. Symptoms may be relieved by flexing the affected leg and weight bearing on the contralateral leg.
Different provocative manoeuvres help distinguish this condition from others causing low back pain. Most commonly used is the FABER (flexion, abduction, external rotation, and extension of the hip to create a figure of four: elicits pain) Patrick test. This is used to increase the predictive value and establish the diagnosis. Radiological imaging is used mainly to exclude red flags.
Treatment follows a multidisciplinary approach. Conservative treatments include exercise therapy and manipulation (address gait and posture imbalance). Intra-articular SJ infiltrations with local anaesthetic and corticosteroids have been found to be effective in most studies.
Regarding piriformis syndrome, which of the following is false? a. It may result from the splitting of piriformis muscle
b. It leads to sciatica
c. Pain decreases with hip flexion, adduction and internal rotation
d. Neurological examination including straight leg raising may be normal
C The piriformis is a muscle in the gluteal region of the lower limb. The piriformis muscle is part of the lateral rotators of the hip and it externally rotates the extended thigh and abducts the flexed thigh. In about 15% of patients, the piriformis muscle is split and pierced by the two components of sciatic nerve. At other times, overuse injury (common in cyclists, runners, tennis players, ballet dancers) of this muscle may cause symptoms. This causes sciatic compression and consequent sciatica (pain in the distribution of sciatic nerve). Pain worsens on squatting, climbing stairs, walking and prolonged sitting. It is typically unilateral.
Diagnostic tests include:
Pace sign: pain and weakness on resisted abduction of flexed thigh in seated position.
Lasègue’s sign: pain on flexion, adduction and internal rotation of hip in a supine patient.
Freiberg’s sign: pain on forced internal rotation of the extended thigh.
Conservative management comprises analgesics, stretching exercises and deep heat using ultrasound. Fluoroscopy-guided piriformis injections using local anaesthetics and corticosteroids are effective. Botulinum toxin injections have shown more effective pain relief. Surgical release is the last
option.
Which of the following is not used in intravenous drug infusion therapy for treatment of neuropathic pain?
a. Lignocaine
b. Magnesium
c. Phentolamine d. Ketamine
C
Intravenous drug infusion may be used to treat neuropathic pain. This uses lignocaine (Na+ channel blocker), ketamine (NMDA antagonist), magnesium (NMDA antagonist), adenosine (presynaptic antinociception by preventing release of substance P) and alfentanil (opioid).
Phentolamine (α-blocker) infusion is used as a diagnostic test for sympathetic mediated pain. If positive, the patient is prescribed oral α- blocker such as doxazocin.
Regarding fibromyalgia syndrome, which of the following is false? a. There are widespread tender points
b. It is more common in females
c. It is often associated with psychiatric complaints
d. It responds best to analgesics
D
Fibromyalgia syndrome is a disorder characterised by chronic generalised pain and allodynia, a heightened and painful response to pressure (tender points). Other symptoms may include fatigue, sleep disturbance, joint stiffness, bowel and bladder abnormalities, paraesthesia, depression and anxiety. It is estimated to affect 2%–4% of the population and is more common in females (nine times).
The American College of Rheumatology (ACR 1990) established criteria for the diagnosis of FMS, including the presence of tenderness at 11 or more of 18 preselected sites (tender points). Additionally, the Fibromyalgia Impact Questionnaire is used to assess the impact of pain on a patient’s life.
A multidisciplinary treatment programme combining behavioural modification, education and physical training is effective.
Regarding post-herpetic neuralgia, which of the following statements is false?
a. It follows acute herpes zoster infection in most instances
b. Non-steroidal anti-inflammatory drugs are very effective in relieving pain c. Amitryptiline is a first-line drug
d. It is hard to treat once established, and therefore it is best prevented by vaccination
B Post-herpetic neuralgia is a debilitating neuralgia following an acute varicella zoster infection (usually after 6 weeks). Typically, it is confined to a dermatomal distribution of the skin. It is difficult to treat once established. Hence both childhood vaccination and early, aggressive treatment of acute herpes zoster infection are vital.
Since it is a neuropathic pain, it is treated first with antidepressants (tricyclic antidepressants like amitryptyline) followed by anticonvulsants (gabapentin).
Opioids may be needed in some (NSAIDs are rarely useful). Topical local anaesthetics and capsaicin may also relieve pain. Intrathecal methylprednisolone with lignocaine as repeated injection can help where non-interventional therapies fail.
Regarding transcutaneous electrical nerve stimulation, which of the following statements is false?
a. It is based on the gate control theory of pain
b. It may be used in epileptic patients
c. It is used for treatment of chronic pain
d. It is contraindicated in patients with cardiac pacemakers
B Melzack and Wall proposed that the transmission of noxious information (C fibre) could be inhibited by activity in large-diameter peripheral afferents (Aβ fibre) (gate control theory of pain). In transcutaneous electrical nerve stimulation (TENS), electric current produced by a device is used to stimulate the nerves for therapeutic purposes (analgesia). Two types of TENS are used.
Indications include acute post-operative pain, labour pain, angina, dysmenorrhoea and chronic pain states.
Contraindications include cardiac pacemakers (interference), pregnancy (can stimulate uterine contractions), bleeding diathesis and epilepsy (may induce seizures).
Which of the following statements is correct?
a. Opioid-induced hyperalgesia is a phenomenon associated with the short- term use of opioids
b. Tolerance occurs because of rightward shift of the dose-response curve c. Pseudotolerance results from prescribing a higher opioid dose than is needed by the patient
d. All of the above
D Tolerance and opioid-induced hyperalgesia result from opioid therapy, but are caused by two distinct mechanisms.
Opioid-induced hyperalgesia (OIH) is a phenomenon associated with the long-term use of opioids. Over time, individuals develop an increasing sensitivity to noxious stimuli (hyperalgesia), such that a non-noxious stimulus evokes a painful response (allodynia). Mechanisms involved in OIH are: spinal NMDA activation, spinal dynorphin release (KOP agonist) and facilitation of descending inhibitory pathways. Treatment options include:
reduction of opioid dose
opioid rotation to methadone or buprenorphine (KOP antagonist) NMDA antagonists (ketamine).
In tolerance, increasing the dose of opioid can overcome it, but doing so in opioid-induced hyperalgesia may worsen the patient’s condition by inducing hyperalgesia while increasing physical dependence. It is important to make a clinical distinction between tolerance (reduction in effect needing an increase of opioid dose to maintain pain relief) and pseudotolerance (request of more opioids by patient as the prevalent dose is insufficient for treating the pain).
