essay 5 - Pain - definition, etiology, classification. Pathways o superficial and deep somatic pain

Give definition of pain

• Pain is a complex, unpleasant sensory and emotional experience associated with actual or potential tissue damage.

• IASP (international association for the study of pain) definition: an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage.

• Kitchel (1987) def: a subjective interpretation of nerve impulses induced peripherally by a stimulus that is actually or potentially noxious to tissue

define pain threshold and pain tolerance

• pain threshold: the minimal intensity at which a stimulus is perceived as painful

• Pain tolerance: the maximum intensity or duration of pain that a person is willing to endure before responding overtly

what are some influences on pain tolerance?

• decreased by: fatigue, anxiety, fear, sleep deprivation, repeated exposure

• inceased by: alcohol, medication, hypnosis, warmth, distractions, belief/faith

pain perception depending on age and sex

• newborn > adults

• adolescents < adults

• elderly report pain more than younger adults

• women > men in perceived pain intensity

what are the different pathways of pain (neuroanatomy)?

1. afferent pathway

2. primary afferent fibers

3. major ascending pain pathways

describe the afferent pathway

• pain begins with activation of nociceptors (pain receptors) which transmit signals via afferent nerve fibers to the spinal cord.

1. Sensor receptors:

— exteroceptive: skin and mucosa

— Interoceptive: internal organs

— Proprioceptive: position of body parts

• Nerve impulse transmission:

1. resting potential: neuron at rest

2. action potential: sodium enters → depolarization

3. repolarization: potassium exits

4. hyperpolarization: neuron overshoots

5. refractory period: ion return to resting state

Describe the primary afferent fibers

• alpha beta

• alpha delta

• c fibres

describe the major ascending pain pathways

1. spinothalamic tract: from body to brain (sharp, local pain)

2. spinoreticular tract/spinoparabrachial tract: carries dull, aching pain

3. trigeminal system: or facial pain (via V1, V2, V3 branches)

what is Gate control theory (Melzack and wall)?

• pain signals via alpha delta and C fibers synapse in the substantia gelatinosa (SG) in the spinal cord

• SG acts as a gate:

— closed gate: decrease t-cell simulation → decrease pain perception

— open gate: increase t-cell simulation → increase pain perception

how is pain classified?

• by cause

• by type

pain classified by cause

1. Nociceptive pain - due to actual tissue damage

• acute physiological: sharp, sudden pain from injury

• pathophysiological: in inflamed/damaged tissues

2. neuropathic pain - nerve injury or disease

• peripheral: e.g trigeminal neuralgia

• central: e.g post-stoke pain

3. chronic pain - lasting >6 months

Includes physical + psychological components (depression, sleep disorders)

pain classified by type

1. Somatic pain

• superficial (cutaneous): sharp, localized (skin/mucosa)

• deep (muscles, joint, bones): dull, aching, poorly localized

2. Visceral pain= internal organs, poorly localized, often referred pain

3. thalamic pain = due to lesions in the thalamus (central processing)

4. Neuropathic pain = from damaged nerves (e. post-hepetic neuralgia)

5. referred pain= perceived in a different area than the actual source (e.g heart attack → jaw pain)

6. phantom pain= felt in limb or body pat that has been amputated

7. psychosomatic pain = real pain linked to motional or psychological factors

clinical features of pain

1. Acute pain response:

• increased heart rate

• increased blood pressure

• sweating (diaphoresis)

• dilated pupils

• hyperglycemia

• decreased gastric mobility and acid secretion

2. Chronic pain response:

• Psychological changes: depression, anxiety, poor sleep, denial

• Pain pathways (face vs body)

— Body = spinothalamic tract (from spinal cord o thalamus)

— face = trigeminal nerve → spinal trigeminal nucleus → thalamus

Describe acute pain response

1. Acute pain response:

• increased heart rate

• increased blood pressure

• sweating (diaphoresis)

• dilated pupils

• hyperglycemia

• decreased gastric mobility and acid secretion

describe the chronic pain response

2. Chronic pain response:

• Psychological changes: depression, anxiety, poor sleep, denial

• Pain pathways (face vs body)

— Body = spinothalamic tract (from spinal cord o thalamus)

— face = trigeminal nerve → spinal trigeminal nucleus → thalamus

describe the types of orofacial pain

• typical facial pain: e.g trigeminal neuralgia

• bone pain: e.g from tumor or fracture

• muscle pain: e.g from bruxism or TMJ dysfunction

• Inflammatory pain

• Ischemic pain - pain caused by a lack of blood supply (ischemia) to a tissue

• sensitization pain: increased response to repeated stimuli

describe the management of orofacial pain

1. pharmacological:

• analgesics: NSAIDs, paracetamol

• narcotics

• antidepressants/ anticonvulsants: for neuropathic pain

• anesthetics: topical or injectable

• anti-inflammatoy/ anti-microbial/antiviral/antihistamine agents

• muscle relaxants , vasoactive agents, neurolytic agents

2. physical therapy

• ultrasounds

• electrogalvanic simulation

• sensory stimulation (TENS, acupuncture)

3. psychological support

• hypnosis

• behavioral therapy

• stress management

what are the pharmacological ways of managing orofacial pain?

1. pharmacological:

• analgesics: NSAIDs, paracetamol

• narcotics

• antidepressants/ anticonvulsants: for neuropathic pain

• anesthetics: topical or injectable

• anti-inflammatoy/ anti-microbial/antiviral/antihistamine agents

• muscle relaxants , vasoactive agents, neurolytic agents

what physical therapy can be done to manage orofacial pain?

2. physical therapy

• ultrasounds

• electrogalvanic simulation

• sensory stimulation (TENS, acupuncture)

what psychological support can be given to manage orofacial pain?

3. psychological support

• hypnosis

• behavioral therapy

• stress management