9. Pain Flashcards
What are the types of pain?
Nociceptive
- pain transmitted by noiceptors
- SOMATIC (soft tissue, bone)
- VISCERAL (less well-localised)
Neuropathic
- pain as a result of damage to the pain system
Noiciplastic
- pain as a result of a modualted pain system eg central sensitisation
what is fibromyalgia
Fibromyalgia is a syndrome characterised by widespread pain throughout the body with tender points at specific anatomical sites
The exact pathophysiology is not known. Hypotheses include:
Peripheral and central hyperexcitability at spinal or brainstem level.
Altered pain perception.
Somatisation.
epidemiology fibromyalgia
women are around 5 times more likely to be affected
typically presents between 30-50 years old
features of fibromyalgia
chronic pain: at multiple site, sometimes ‘pain all over’
lethargy
cognitive impairment: ‘fibro fog’
sleep disturbance, headaches, dizziness are common
Symptoms are generally reported as worse in cold, humid weather and under times of stress
diagnosis of fibromyalgia
clinical
may refer to American college pf rheumatology classification criteria which lists 9 pairs of tender points on the body. If a patient is tender in at least 11 of these 18 points it makes a diagnosis of fibromyalgia more likely
management fibromyalgia
aerobic exercise: has the strongest evidence base
NICE advises that gabapentinoids, including pregabalin, should not be offered to people with chronic primary pain
However SIGN recommends that clinicians should consider pregabalin for people with fibromyalgia, but states that this is outwith the marketing authorization
neuropathic pain guidance
first-line treatment*: amitriptyline, duloxetine, gabapentin or pregabalin
if the first-line drug treatment does not work try one of the other 3 drugs
in contrast to standard analgesics, drugs for neuropathic pain are typically used as monotherapy, i.e. if not working then drugs should be switched, not added
tramadol may be used as ‘rescue therapy’ for exacerbations of neuropathic pain
topical capsaicin may be used for localised neuropathic pain (e.g. post-herpetic neuralgia)
pain management clinics may be useful in patients with resistant problems
*please note that for some specific conditions the guidance may vary. For example carbamazepine is used first-line for trigeminal neuralgia
causes of neuropathic pain
radiculopathy
Postherpetic neuralgia (post-shingles)
Trigeminal neuralgia
Nerve damage, including postoperative.
Pain because of cancer tumour infiltration.
Peripheral neuropathy:
A – Alcohol
B – B12 deficiency
C – Cancer and Chronic Kidney Disease
D – Diabetes and Drugs (e.g. amiodarone, metronidazole, cisplatin, phenytoin, isoniazid, nitrofurantoin)
E – Every vasculitis
pathophysiology of neuropathic pain
Neuropathic pain may be defined as pain which arises following damage or disruption of the nervous system. It is often difficult to treat and responds poorly to standard analgesia.
Neuropathic pain is characterised by continuous or intermittent spontaneous pain, typically described as burning, aching or shooting in nature. The pain may be provoked by normally innocuous stimuli (allodynia). Neuropathic pain is also commonly associated with hyperalgesia (increased pain intensity evoked by normally painful stimuli), paraesthesia and dysaesthesia.
causes of peripheral neuropathy
A – Alcohol
B – B12 deficiency
C – Cancer and Chronic Kidney Disease
D – Diabetes and Drugs (e.g. amiodarone, metronidazole, cisplatin, phenytoin, isoniazid, nitrofurantoin)
E – Every vasculitis
Presentations different types of diabetic peripheral neuropathy
A-alpha/A-delta (larger sensory fibres)
- distal symmetrical sensory neuropathy
- touch, vibration and proprioception defecits
A-delta/C
- Caused by loss of small sensory fibres.
- Presents with deficits in pain and temperature sensation in a glove and stocking distribution along with episodes of burning pain.
Autonomic nerves (very small)
Autonomic Neuropathy
Presents with postural hypotension, gastroparesis, constipation, urinary retention, arrhythmias and erectile dysfunction.
Mononeuritis multiplex
Diabetic Amyotrophy
Caused by inflammation of lumbosacral plexus or cervical plexus.
Severe pain around the thighs and hips.
Proximal weakness.
How does gastroparesis present? diabetes
symptoms include erratic blood glucose control, bloating and vomiting
management options include metoclopramide, domperidone or erythromycin (prokinetic agents)
cause, pathophysiology and presentation alcoholic neuropathy
secondary to both direct toxic effects and reduced absorption of B vitamins
sensory symptoms typically present prior to motor symptoms
Alcoholic neuropathy is damage to the nerves that results from excessive drinking of alcohol. The damage may affect the autonomic nerves (those that regulate internal body functions) and the nerves that control movement and sensation.
what vitamin deficiency is associated with peripheral neuropathy?
A lack of B12 damages the myelin sheath that surrounds and protect nerves. Without this protection, nerves cease to function properly and conditions such as peripheral neuropathy occur. Even B12 deficiency that is relatively mild may affect the nervous system and the proper functioning of the brain.
what neuropathic pain syndorme is treated differently?
trigeminal neuralgia
- Carbamazepine
pathophysiology trigeminal nauralgia?
Most cases are idiopathic but compression of the trigeminal roots by tumours or vascular problems could be the cause.
red flags trigeminal neuralgia
looking for non-idiopathic cause ef tumour or vascualr problems
Red flags:
Sensory changes
Deafness or other ear problems
History of skin or oral lesions that could spread perineurally
Pain only in the ophthalmic division of the trigeminal nerve (eye socket, forehead, and nose), or bilaterally
Optic neuritis
A family history of multiple sclerosis
Age of onset before 40 years
when should you refer someone with tirgeminal neuralgia? to who?
Failure to respond or atypical features should prompt referral to neurology
Presentation trigeminal neuralgia
Severe unilateral pain, often triggered by touching the skin, brief electric shock like pains, abrupt in onset and termination
Triggers
Light touch, washing, shaving, mocking, talking, brushing teeth. Particularly of nasolabial fold.
what is shingles?
Shingles (herpes zoster infection) is an acute, unilateral, painful blistering rash caused by reactivation of the varicella-zoster virus (VZV). Following primary infection with VZV (chickenpox), the virus lies dormant in the dorsal root or cranial nerve ganglia.
features shingles
Features
prodromal period
burning pain over the affected dermatome for 2-3 days
pain may be severe and interfere with sleep
around 20% of patients will experience fever, headache, lethargy
rash
initially erythematous, macular rash over the affected dermatome
quickly becomes vesicular
characteristically is well demarcated by the dermatome and does not cross the midline. However, some ‘bleeding’ into adjacent areas may be seen
most commonly affected dermatomes shingles
The most commonly affected dermatomes are T1-L2.
management shingles
- remind patients they are potentially infectious
may need to avoid pregnant women and the immunosuppressed
should be advised that they are infectious until the vesicles have crusted over, usually 5-7 days following onset
covering lesions reduces the risk
+ anaglgesia
paracetamol and NSAIDs are first-line
if not responding then use of neuropathic agents (e.g. amitriptyline) can be considered
oral corticosteroids may be considered in the first 2 weeks in immunocompetent adults with localized shingles if the pain is severe and not responding to the above treatments
+ antivirals
within 72 hours for the majority of patients, unless the patient is < 50 years and has a ‘mild’ truncal rash associated with mild pain and no underlying risk factors
one of the benefits of prescribing antivirals is a reduced incidence of post-herpetic neuralgia, particularly in older people
aciclovir, famciclovir, or valaciclovir are recommended
complication shingles?
post-herpetic neuralgia
the most common complication
more common in older patients
affects between 5%-30% of patients depending on age
most commonly resolves with 6 months but may last longer
