Pain Classification: Nociceptive, Neuropathic, Central and Mixed - PowerPoint Presentation

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Pain Classification:Nociceptive, Neuropathic, Central and Mixed

Rachael Rzasa Lynn, MD

Chronic Pain Zoom Webinar

2 December 2015Slide2

Definitions

Most basic = neurophysiologic classification

based

on

presumed mechanism

of pain.

Simplified, there are 2 types of pain:

nociceptive pain

non

-nociceptive

pain

Neuropathic pain

Idiopathic pain

≠psychogenic pain!Slide3

Nociceptive Pain

Pain due to continuous tissue injury

actual or threatened damage to non-neural tissue results in activation of peripheral

nociceptors

noxious

stimulus  electrochemical impulses in peripheral nerves  spinal cord  brain= transduction, transmission, modulation, and perceptionExamples: arthritis pain, acute post-traumatic painSubdivided into somatic pain and visceral pain

Basbaum

et al.

Cell

2009; 139:

267-284Slide4

Nociceptive Pain

Somatic pain

excitation and/or sensitization

of

nociceptors

in tissues such as bone, periarticular soft tissue, joints, and muscles Well localizedIntermittent or constant“aching,” “stabbing,” “gnawing,” “throbbing”Slide5

Nociceptive Pain

Visceral pain

Not produced by all

visceral

organs

Liver, kidney, most solid viscera, and lung parenchyma are not sensitive to pain.Not always created by visceral injury Cutting intestine causes no pain, stretching of the bladder is painfulDiffuse and poorly localizedNo separate visceral sensory pathway and low proportion of afferent nerve fibers from visceraIntermittent or constant“dull,” “colicky,” “squeezing”Referrs to other

locations.Accompanied by motor and autonomic reflexes

Eg

, nausea

, vomiting,

muscle tension, etc.Slide6

Neuropathic Pain

“Pain

arising as a direct consequence of a lesion or disease affecting the somatosensory system

.”

at

any point(s) within the somatosensory pathwaysPain from lesion/disease sustained by aberrant processing in the peripheral and/or central nervous systemtypically described as “sharp” or “burning”This is a clinical description (NOT a diagnosis) According to IASP,“this requires a demonstrable lesion or a disease that satisfies established neurological diagnostic criteria.”“The presence of symptoms or signs (e.g., touch-evoked pain) alone does not justify the use of the term

neuropathic.”“It is

common…that

diagnostic testing may yield inconclusive or even inconsistent data. In such instances, clinical judgment is required to reduce the totality of findings in a patient into one putative diagnosis or concise group of diagnoses

.”Slide7

Neuropathic Pain

Subsets

Peripherally

generated pain:

involves such

cervical or lumbar radiculopathy, spinal nerve lesions, and brachial or lumbosacral plexopathiesCentrally generated pain:involves injury to the central nervous system at the level of the spinal cord or above. Sympathetically maintained pain:may be generated peripherally or centrallycharacterized by localized autonomic dysregulationvasomotor or sudomotor changes, edema, sweating, trophic changes including atrophyComplex Regional Pain SyndromeSlide8

Central Pain States

Central pain

: Pain initiated or caused by a primary lesion or dysfunction in the central nervous system.

Can be produced by an type of vascular

, demyelinating, infectious, inflammatory, or traumatic lesion in the

brain or spinal cordEg, post-stroke painCentral sensitization: Increase in the excitability of neurons in the spinal cord.Increased responsiveness of nociceptive neurons in the central nervous systemIncreased response to input to which they normally respondActivation in response to subthreshold inputSlide9

IASP Pain Classification

Multidimensional

Classification of

Pain

Developed to standardize descriptions of pain syndromes and provide a point of reference

Uses 5 axes to classify chronic painRegion of the body affected (Axis I),System whose abnormal functioning could produce the pain (Axis II),Temporal characteristics of pain and pattern of occurrence (Axis III),Patient's statement of intensity and time since onset of pain (Axis IV)Mild, medium or severe, each for ≤1 month, 1-6 months or >6 months durationPresumed Etiology (Axis V

)Infection, inflammation, neoplasm, toxic, metabolic, etc

Uses the above to create 5-digit code assigned to each chronic pain diagnosis

Limitations: Does not include psychosocial or behavioral data

ALL PAIN HAS A PSYCHOLOGICAL COMPONENTSlide10

Proposed Taxonomy of Pain Based upon Multifactorial Assessment

Pain

Parameters:

Anatomy/System

Duration/Intensity/Quality

Associated Abnormality (physical/psychological)Underlying Diseases:Signs/SymptomsPain Mechanisms:NEUROPHYSIOLOGICALPrimary afferent involvementCNS involvementPSYCHOLOGICALCognitive-Affective-Behavioral InvolvementCognitive appraisal of painCoping

Affect/moodEnvironment Slide11

Mixed Pain

Most pain is mixed

Even “nociceptive pain” can lead to central sensitization

Eg

, osteoarthritis

fMRI and PET changesIncreased activation in brain areas involved with affect, aversive conditioning and motivation than experimental painThese patients display hyperalgesia locally and in areas distant from the arthritic jointAfter THA, these patients display reduced pain in both areasALL pain has a psychological component!

Aranda

-Villalobos P et al. Arthritis & Rheumatism 2013; 65:

1262-1270.

Sofat

et al.

Rheumatology

2011; 50:

2157-2165Slide12

TRP: Transient

receptor potential

channel (many subtypes)

TRPA1=cold

(<15°C) in injury (not normal, acute cold), menthol TRPM8=cold(<25°C), menthol TRPV1=heat (>43°C), capsaicinASICs: Acid-sensing ion channelsKCNK: Potassium channel subtypesNav: Voltage-gated sodium channel isoformsAlso Voltage-gated Calcium channels (N- and T-type); α2δ subunit ↑’d after injury Mechanical transduction may occur via TRP, ASIC and/or KCNK channels

Grace PM, et al.

Nat Rev

Immunol

.

2014;

14: 217-

231

Basbaum

et al. Cell 2009; 139: 267-284Slide13

Mechanistic Stratification of Medications Used

to Treat Neuropathic Pain

Fig. 4. Mechanistic stratification of antineuralgic agents. PNS = peripheral nervous system; CBZ = carbamazepine; OXC = oxcarbazepine; PHT = phenytoin; TPM = topiramate; LTG = lamotrigine; TCA = tricyclic antidepressant; NE = norepinephrine; SSRI = selective serotonin re-uptake inhibitor; SNRI = serotonin and norepinephrine re-uptake inhibitor; GBP = gabapentin; LVT = levetiracetam; NMDA = N-methyl-D-aspartate; NSAID = nonsteroidal anti-inflammatory drug.

Beydouna

&

Backonja

M.

J Pain Symptom Manage.

2003;25:S18-30