L17 - Pain Flashcards
1. Revise peripheral and central neural pathways that subserve pain 2. Learn about localisation in pain syndromes - ranging from small fibre peripheral neuropathy to thalamic infarction 2. Understand complex regional pain syndromes and phantom limb phenomenon. 3. Know difference between primary and secondary head aches. 4. Understand that primary headache disorders differ from other types of pain and are managed differently, and know the important types of primary headache - migraine, cluster
Definition of pain?
Unpleasant sensory, emotional experience associated with actual or potential tissue damage
Hyperalgesia
Increased response to stimulus that is normally painful
Dysaesthesia
An unpleasant abnormal sensation, whether spontaneous or evoked
Hypoalgesia
Diminished response to a normally painful stimulus.
Analgesia
Absence of pain in response to stimulation that normally is painful
Hyperaesthesia
Increased sensitivity to stimulation, excluding special senses
Hypoaesthesia
Diminished sensitivity to stimulation, excluding special senses
Hyperpathia
An increased sensitivity with increasing threshold to repetitive stimulus.
Paraesthesia
An abnormal sensation whether spontaneous or evoked
Allodynia
Pain resulting from stimulus (light touch) that does not normally elicit pain
Briefly summarise the types of pain
Nociceptive pain - somatic (relating to body) - visceral (organs) Neuropathic pain - sympathetic, peripheral, central
What is nociceptive pain?
Usually acute, develops in response to a specific situation.
What are nociceptors and their role?
Nociceptors - specialised nerve cells
Detect noxious stimuli
- extreme heat
- cold
- pressure
- pinching
- chemicals
Examples of Noxious stimuli?
Noxious stimulus - potentially tissue damaging event.
- Mechanical
- pinching, other tissue deformation - Thermal
- high / low temp - Chemical
- acid / irritant
What is neuropathic pain?
Caused by damage or disease affecting somatosensory nervous system.
- primary lesion or dysfunction in nervous system
Describe peripheral neuropathic pain?
Peripheral
- Aberrant regeneration of neurones may cause them to become unusually sensitive.
- May develop spontaneous pathological activity.
State the different fibres in primary afferent neurones?
C - Fibre
A(delta)- Fibre
A(beta) - Fibre
C - Fibre
Smallest
Un-myelinated
Slow, diffuse, dull pain
A(delta) - Fibres
Still small
Activated by mechanical and thermal stimuli.
Cause rapid, sharp, localised pain.
A(beta) - Fibres
Large diameter
Highly myelinated
sensation- light touch, non-noxious
Role of noradrenaline in pain?
Involved with descending modulation of pain
Role of Substance P in pain?
- Identified in C-Type sensory nerve ending.
- Associated with inflammation.
- Can be synthesised and released from immune cells such as macrophages and eosinophils.
Role of glutamate in pain?
what is glutamate important in?
- Glutamate = main excitatory neurotransmitter in mammal nervous system.
- Involved in central sensitisation
- Glutamate important:
- brain development
- learning
- memory storage
- nociceptive processing
What is central sensitization?
Development and maintenance of chronic pain.
Nociceptive processing
Perception of pain sensations
Give examples of symptoms of loss of sensation?
Negative (loss of sensation)
- touch
- vibration
- proprioception (perception or awareness of position and movement of body)
- pain
- temp
Examples of symptoms which involve gain of a sensation?
Positive
- burning
- shooting
- hyperalgesia (increased sensitivity to pain)
- Paresthesia
- allodynia
Paresthesia
Abnormal dermal sensation with no apparent physical cause.
What pathways does the spinothalamic tract consist of?
Anterior
Lateral
What information is carried in the anterior spinothalamic tract?
Crude touch
ACT
What information is carried in the lateral spinothalamic tract?
Pain and temperature
Where does the decussation of the spinothalamic tract occur?
Level of spinal cord.
Not the brain stem like
- dorsal column-medial lemniscus pathway
- lateral corticospinal tract
Describe the fibres of the lateral spinothalamic tract?
Composed of:
- fast-conducting, sparsely myelinated A(delta) fibres.
- slower, unmyelinated C fibres
Which fibres carry sensory information in the anterior spinothalamic tract?
A(beta) fibres carry sensory info pertaining to crude touch from the skin.
Where does a lower motor neuron lesion affect?
Nerve fibres travelling from :
- ventral horn…
- to anterior grey column of spinal cord…
- to relevant muscles….
Flaccid paralysis
Paralysis accompanied by loss of muscle tone.
What are symptoms of a lower motor neurone lesion?
- Muscle paralysis
- Fasciculations
- –> caused by increased receptor conc on muscles to compensate for lack of innervation.
What reflex is often missing when patient has lower motor neuron lesion?
Plantar reflex (babinski)
- elicited when sole of foot is stimulated with a blunt instrument.
- in a normal patient plantar reflex causes a downward response
An upward response = babinski response, can identify disease of spinal cord and brain in adults.
Mononeuropathy
One nerve involved
Mononeuropathy multiplex
- Asymmetrical damage to single nerves.
e. g Right arm and left leg affected
Polyneuropathy
Symmetrical
common cause: diabetes, although alcohol can also be a factor
What is a common cause of mononeuropathy?
Carpal tunnel syndrome
Common cause of mononeuropathy multiplex?
Diabetes
Vasculitis
What is multiple sclerosis?
Condition that affects your brain and spinal cord.
- Immune system attacks myelin
- forms lesions
- disrupts messages traveling along nerve fibres
State some examples of patterns of damage to nerves?
- Wallerian degeneration
- Segmental demyelination
- Axonal degeneration
Wallerian degeneration
- Active process of degeneration.
- Nerve fibre cut.
- Part of axon distal to injury degenerates.
- Axonal degeneration followed by:
- —> degradation of myelin sheath
- —> infiltration by macrophages.
Describe segmental demyelination?
- Focal degeneration of myelin sheath, sparing axon.
- Often immune mediated or inflammatory in origin.
CIDP
- chronic inflammatory demyelinating polyneuropathy
Describe axonal degeneration?
Can occur with age >60 y/o
Starts distally.
Common cause:
- diabetes, alcohol, toxins
Briefly describe causes of mononeuropathy?
- Trauma
- Entrapment / compression
- Infection
- Systemic illnesses:
- diabetes mellitus
- sarcoidosis
- vasculitis
- leprosy
Recap: Diabetes Mellitus
Type 1: body cannot produce insulin needed to control BG.
Type 2: body cannot produce enough insulin, insulin ineffective.
Sarcoidosis
Disease involving abnormal collections of inflammatory cells that form lumps known as granulomas.
- develop on organs, usually lungs and skin
Leprosy
lmao ice-age, diego’s got the L word
Caused by Mycobacterium Leprae.
Disfiguring pale skin sores.
Nerve damage:
- loss of feeling in arms and legs
- muscle weakness
v. long incubation period, almost 3 to 5 years.
Briefly state 4 ways of Polyneuropathy classification?
- Distribution
- symmetrical vs asymmetrical, proximal vs distal - Functional disturbance
- motor, sensory, autonomic, mixed - Mode of onset
- acute, subacute, chronic - Pathological process
- axonal, demyelinating
Briefly describe the pathophysiology of diabetic polyneuropathy?
- Poor glycaemic control
- accumulation of sorbitol and fructose in axon/ schwann cells
- occlusion of nutrient vessels supplying nerves
Describe Varicella Zoster?
where does it stay dormant?
DNA herpes zoster virus.
Stays dormant within the dorsal root after initial infection.
Sciatica
Irritation of the sciatic nerve causing pain.
- pain in lower back to behind the thigh, radiating down below the knee.
What is the most common cause of sciatica?
Prolapsed disc.
Describe the SLR test for sciatica?
SLR - straight leg raise
Patient supine, clinician lifts leg until patients complain.
Degree of hip flexion may indicate condition
What is Syringomyelia
Development of fluid filled cyst in spinal cord.
Describe clinical features associated with Syringomyelia?
- Dissociated sensory loss of pain and temperature.
- Wasting and weakness of small muscles of hand.
- Winging of scapula
Explain the ‘cape like’ distribution of pain in syringomyelia?
Compression of area of decussation of spinothalamic tract.
- dysfunction of fibers that pass through the anterior white commissure.
What is Horner’s syndrome?
Rare disorder characterized by:
- constricted pupil (miosis)
- drooping of upper eyelid (ptosis)
- absence of sweating of face (anhidrosis)
- shrinking of eyebacll into body cavity that protects eye (enophthalmos)
What is complex regional pain syndrome?
Poorly understood condition where a person experiences persistent severe and debilitating pain.
- skin of affected body part can become so sensitive, slight touch or bump or even change in temp can cause intense pain
Describe type 1 CRPS?
Complex regional pain syndrome
aka: Reflex sympathetic dystrophy
Occurs after an illness or injury that didn’t directly damage nerves in affected limb.
Describe type 2 CRPS?
Causalgia
- defined nerve injury
State some symptoms of CRPS?
Pain - burning, allodynia. hyperalgesia Loss of hair, nail changes, oedema and shininess Warm or cold limb Sweating Tremor
Describe phantom limb pain?
Common in patients post amputation.
Sensation body part is still present.
What is the difference between primary and secondary headaches?
Primary
- no underlying cause
Secondary
- cause, underlying abnormality
Examples of primary headaches?
Migraine
Cluster headache
Trigeminal autonomic cephalalgias
Group of headache disorders characterised by attacks of moderate to severe unilateral pain in head or face.
Give examples of some secondary headaches?
Thunderclap headache
Hydrocephalus as a result of raised intracranial pressure.
Pyrexia
Rise in body’s core temp.
Reduces severity of illness by preventing bacteria and viruses from multiplying.
Describe a migraine
Pulsatile, unilateral, moderate-severe headache which builds up over 1-2hrs
What is a cluster headache?
Relatively short but EXTREMELY SEVERE neuropathic pain every day for weeks or months at a time.
Describe Trigeminal neuralgia?
Neuropathic pain in the distribution of the trigeminal nerve (usually 2nd and 3rd)
- persistent dull ache of the face
Neuralgia
Severe, shooting pain occuring due to a damaged or irritated nerve.
