Somatic sensation and pain - NeurologyHomePageneurology.pote.hu/neuro/modules/stud/data/061009e.pdf · Free nerve endings -hairy & hairless skin -C fibers ... • Somatic pain originates

SOMATIC SENSATION AND PAINSOMATIC SENSATION AND PAIN

ZoltZoltáánn PfundPfund, MD, PhD, MD, PhD

University of PUniversity of PéécscsDepartment of NeurologyDepartment of Neurology

CONTENTSCONTENTS

•• Anatomy and physiology of somatic sensationAnatomy and physiology of somatic sensation

•• InterruptionInterruption ofof sensory pathwayssensory pathways

•• Pain and Pain and nociceptionnociception

•• Anatomy and physiology of painAnatomy and physiology of pain

•• Pain disordersPain disorders

•• Therapy of painTherapy of pain

University of PUniversity of Péécscs, Department of Neurology, Department of Neurology

SENSORY AFFERENTS SENSORY AFFERENTS CUTAN MECHANORECEPTORSCUTAN MECHANORECEPTORS



•• Fast Adapting TouchFast Adapting Touch--Pressure ReceptorsPressure ReceptorsHair follicle receptorHair follicle receptor

MeissnerMeissner endings endings –– hairless skin hairless skin –– AAββRespond to fRespond to flutter, motionlutter, motion

PacinianPacinian corpuscle corpuscle –– dermis dermis –– AAββResponds to vResponds to vibrationibration



•• Slowly Adapting TouchSlowly Adapting Touch--Pressure ReceptorsPressure Receptors

Free nerve endings Free nerve endings -- hairy & hairless skin hairy & hairless skin -- C fibersC fibers

Tickle & light or superficial touchTickle & light or superficial touch

MerkelsMerkels discsdiscs -- in both hairy and hairless skin in both hairy and hairless skin –– AAββPressure, form, texturePressure, form, texture

RuffiniRuffini endingsendings -- hairy and some in hairless skin hairy and some in hairless skin -- AAββRespond to lateral stretch of the skin and Respond to lateral stretch of the skin and

steady pressuresteady pressure


SENSORY AFFERENTS SENSORY AFFERENTS JOINT JOINT && MUSCLE RECEPTORSMUSCLE RECEPTORS

•• ProprioceptiveProprioceptive ReceptorsReceptors

Receptors in muscles, tendons and jointsReceptors in muscles, tendons and joints

Joint afferents Joint afferents –– diverse receptors diverse receptors –– AAααProtective functionProtective function

Muscle spindle is a major stretch receptor Muscle spindle is a major stretch receptor -- AAββRespond to muscle lengthRespond to muscle length

GolgiGolgi organs in tendons organs in tendons -- AAααRespond to muscle tensionRespond to muscle tension


SENSORY AFFERENTS SENSORY AFFERENTS TEMPERATURE RECEPTORSTEMPERATURE RECEPTORS

•• Temperature ReceptorsTemperature ReceptorsSeparate warm and cold receptorsSeparate warm and cold receptors

Free nerve endingsFree nerve endings

Warm receptors Warm receptors -- C fibersC fibers

Respond to increasing temperatureRespond to increasing temperature

Cold receptors Cold receptors -- AAδδ fibersfibers

Respond to decreasing temperatureRespond to decreasing temperature


SENSORY AFFERENTSSENSORY AFFERENTSNOCICEPTORSNOCICEPTORS

•• NocioceptorsNocioceptorsFree nerve endings:Free nerve endings: mechanomechano and and thermoreceptorsthermoreceptors, ,

polymodal nociceptorspolymodal nociceptors

C fibers C fibers –– dull/burning paindull/burning pain –– slow painslow pain

AAδδ fibers fibers -- sharp pricking & stinging painsharp pricking & stinging pain –– fast painfast pain


SENSORY AFFERENTSSENSORY AFFERENTSPRIMARY AFFERENT FIBERSPRIMARY AFFERENT FIBERS

LargeLarge II AAαα 1212--2020 µµmm 7272--120120 m/secm/sec

MediumMedium IIII AAββ 66--1212 µµmm 3636--7272 m/secm/sec

SmallSmall IIIIII AAδδ 11--66 µµmm 44--3636 m/secm/sec

UnmUnmyelinatedyelinated IVIV CC 0.20.2--1.51.5 µµmm 0.40.4--2.02.0 m/secm/sec


SOMATOSENSORY PATHWAYSSOMATOSENSORY PATHWAYS

•• Dorsal ColumnDorsal Column--Medial Medial lemniscallemniscal systemsystemDiscriminative touchDiscriminative touch

Vibratory senseVibratory sense

Limb and joint position informationLimb and joint position information

•• AnterolateralAnterolateral systemsystemPainPain

TemperatureTemperature

Crude touchCrude touch


DORSAL COLUMN DORSAL COLUMN –– MEDIAL MEDIAL LEMNISCAL SYSTEMLEMNISCAL SYSTEM

•• Primary afferents ascend to the medullaPrimary afferents ascend to the medulla

on the on the ipsilateral ipsilateral side of the cord in the side of the cord in the

posterior columns posterior columns

•• Secondary afferents cross in the medulla Secondary afferents cross in the medulla

and ascend as the medial and ascend as the medial lemniscuslemniscus

•• In the thalamus they synapse in the VPL In the thalamus they synapse in the VPL

((ventroposterior ventroposterior lateral nucleus) and ascend lateral nucleus) and ascend

to the cortexto the cortex


ANTEROLATERAL SYSTEMANTEROLATERAL SYSTEM

•• Primary afferents enter the cord laterallyPrimary afferents enter the cord laterally

and synapse in the dorsal hornand synapse in the dorsal horn

•• TheThe secondary afferents cross to the secondary afferents cross to the

opposite side of the spinal cord and ascend opposite side of the spinal cord and ascend

in the spinothalamic tractin the spinothalamic tract

•• TThehe spinothalamic tractspinothalamic tract enterenterss thethe VPLVPL of of

the thalamusthe thalamus,, synapses andsynapses and isis finally carried finally carried

to cortex by the thalamocortical neurons to cortex by the thalamocortical neurons



Pain afferents Pain afferents travel one or two segments up or down the cordtravel one or two segments up or down the cordbefore synapsingbefore synapsing.. Lissauer's tractLissauer's tract isis the tract carrying these the tract carrying these migrating axonsmigrating axons,, but they are only in the tract forbut they are only in the tract for aa short timeshort time. . Within one or twoWithin one or two levelslevels,, they enter the dorsal horn and synapsethey enter the dorsal horn and synapse..


Lissauer`s tract


TheThe dorsal horndorsal horn is ais a multimulti--layered structurelayered structure. The. The thin outermost layerthin outermost layer is is called the posterior marginalis layercalled the posterior marginalis layer. The. The wide pale second layerwide pale second layer isis called called tthe substantia gelatinosa, and the layer deep to that is called the substantia gelatinosa, and the layer deep to that is called the nucleus he nucleus ppropriusroprius..



The two types of pain fibers enter different layers of the dorsaThe two types of pain fibers enter different layers of the dorsal horn. l horn. AAδδ fibers enter the posterior marginalis and the nucleus proprius,fibers enter the posterior marginalis and the nucleus proprius, and and synapse on a second set of neurons. The C fibers enter the substsynapse on a second set of neurons. The C fibers enter the substantia antia gelatinosa and synapse, but they do not synapse on secondary affgelatinosa and synapse, but they do not synapse on secondary afferents. erents. Instead they synapse on interneurons Instead they synapse on interneurons -- neurons which do not project neurons which do not project out of the immediate area. The interneurons must carry the signaout of the immediate area. The interneurons must carry the signal to the l to the secondary afferents in either the posterior marginalis or the nusecondary afferents in either the posterior marginalis or the nucleus cleus proprius. proprius. University of PUniversity of Péécscs, Department of Neurology, Department of Neurology

INTERRUPTION OF SENSORY INTERRUPTION OF SENSORY PATHWAYSPATHWAYS

Hemispheric lesion:Hemispheric lesion:Contralateral Contralateral side of the bodyside of the body




Brainstem:Brainstem:Alternate syndromesAlternate syndromes



Spinal cord:Spinal cord:SegmentalSegmental



Peripheral:Peripheral:RootRoot, p, plexuslexus or peripheral nerveor peripheral nerve

PAIN AND NOCICEPTIONPAIN AND NOCICEPTION

•• Pain is a subjective experience that accompanies Pain is a subjective experience that accompanies nociception, but can also arise without any nociception, but can also arise without any stimulistimuli. It . It includes the includes the emotionalemotional response.response.

•• Nociception is a Nociception is a neurophysiologicneurophysiologic term and denotes the term and denotes the activity in the nerve pathways. These pathways transmit activity in the nerve pathways. These pathways transmit the unpleasant signals that are not always painful. the unpleasant signals that are not always painful.

•• Pain is a critical component of the Pain is a critical component of the bodybody's defense system's defense system

•• CCognitiveognitive and and emotionalemotional factors might dramatically factors might dramatically influence painful sensationsinfluence painful sensations

•• According to WHO one human being out of five suffers According to WHO one human being out of five suffers from chronic painfrom chronic pain


PAIN AND NOCICEPTIONPAIN AND NOCICEPTION

•• Pain is a subjective experience that accompanies Pain is a subjective experience that accompanies nociception, but can also arise without any nociception, but can also arise without any stimulistimuli. It . It includes the includes the emotionalemotional response.response.

•• Nociception is a Nociception is a neurophysiologicneurophysiologic term and denotes the term and denotes the activity in the nerve pathways. These pathways transmit activity in the nerve pathways. These pathways transmit the unpleasant signals that are not always painful. the unpleasant signals that are not always painful.

•• Pain is a critical component of the Pain is a critical component of the bodybody's defense system's defense system

•• CCognitiveognitive and and emotionalemotional factors might dramatically factors might dramatically influence painful sensationsinfluence painful sensations

•• According to WHO one human being out of five suffers According to WHO one human being out of five suffers from chronic painfrom chronic pain


NOCICEPTIONNOCICEPTION

•• Nociceptors are the free nerve endings of neurons thatNociceptors are the free nerve endings of neurons that

have their cell bodies outside the have their cell bodies outside the spinal columnspinal column in the in the dorsal dorsal

root ganglionroot ganglion

•• When the When the nociceptorsnociceptors are stimulated, they transmit signals are stimulated, they transmit signals

through sensory neurons in the spinal cordthrough sensory neurons in the spinal cord

•• Signals release Signals release glutamateglutamate, an exicitory , an exicitory neurotransmitterneurotransmitter

that relays signals from one neuron to another and ultimately that relays signals from one neuron to another and ultimately

to the to the thalamusthalamus, in which pain perception occurs, in which pain perception occurs

•• From the thalamus, the signal travels to the From the thalamus, the signal travels to the cerebrumcerebrum, ,

at which point the individual becomes fully aware of the painat which point the individual becomes fully aware of the pain


ANATOMY AND PHYSIOLOGY ANATOMY AND PHYSIOLOGY OF PAINOF PAIN

–– Neurotransmission by C neurons involves substance P Neurotransmission by C neurons involves substance P

–– AA--δδ transmitters at terminals: glutamate, transmitters at terminals: glutamate, aspartateaspartate, , adenosinadenosin triphosphatetriphosphate

–– Opiates (receptors in lamina II) decreases substance P and Opiates (receptors in lamina II) decreases substance P and lamina II neurons release lamina II neurons release enkephalinsenkephalins, endorphins and , endorphins and dynorphinsdynorphins



Spinal afferent tractsSpinal afferent tracts

–– Lateral Lateral spinothalamicspinothalamic tract (fast conducting tract (fast conducting pathway) via anterior pathway) via anterior comissurecomissure, termination in , termination in brainstem and thalamic structuresbrainstem and thalamic structures

–– Medial Medial spinothalamicspinothalamic tract; tract; paleospinothalamicpaleospinothalamicpathway (slowpathway (slow--conducting conducting multineuronmultineuron system), system), mediates poorly localized pain from deep somatic mediates poorly localized pain from deep somatic and visceral structures. Connections to medulla, and visceral structures. Connections to medulla, parabrachialparabrachial region, midbrain reticular formation region, midbrain reticular formation and hypothalamusand hypothalamus



Thalamic terminus and Thalamic terminus and thalamocorticalthalamocortical projectionsprojections

–– Lateral division terminates in the Lateral division terminates in the ventrobasalventrobasal and and posterior groups of nuclei; projections to the primary posterior groups of nuclei; projections to the primary sensory cortex and sensory cortex and SylvianSylvian fissurefissure

–– Medial divisions terminates in the Medial divisions terminates in the intralaminarintralaminar complex; complex; projections to hypothalamus, projections to hypothalamus, amygdaloidamygdaloid nuclei and nuclei and limbic cortex (arousal and autonomic responses)limbic cortex (arousal and autonomic responses)

–– PaleospinothalamicPaleospinothalamic fibers project onto the medial fibers project onto the medial intralaminarintralaminar nuclei; cortical projection is not well knownnuclei; cortical projection is not well known


DESCENDING PAINDESCENDING PAIN--MODULATING MODULATING SYSTEMSSYSTEMS

–– Projections from the frontal cortex and Projections from the frontal cortex and hypothalamus to the hypothalamus to the periaqueductalperiaqueductal region of region of the midbrain and medullathe midbrain and medulla

–– From the medulla it descends to the lateral From the medulla it descends to the lateral funiculusfuniculus and posterior hornand posterior horn

–– Modulate activity of Modulate activity of nociceptivenociceptive pathwayspathways

–– Other descending pathways (Other descending pathways (serotoninergicserotoninergic, , noradrenergicnoradrenergic) project to locus ) project to locus ceruleusceruleus, dorsal , dorsal rapheraphe nucleusnucleus


DESCENDING PAINDESCENDING PAIN--MODULATING MODULATING SYSTEMSSYSTEMS

Opiate interneurons in the spinal cord can be activated by desceOpiate interneurons in the spinal cord can be activated by descending nding projections from the brainstem (especially the raphe nuclei and projections from the brainstem (especially the raphe nuclei and periaqueductal periaqueductal grey), and can block pain transmission at two sites. 1grey), and can block pain transmission at two sites. 1.,., They can prevent the They can prevent the primary afferent from passing on its signal by blocking neurotraprimary afferent from passing on its signal by blocking neurotransmitter release, nsmitter release, and 2and 2.,., they can inhibit the secondary afferent so it does not send the they can inhibit the secondary afferent so it does not send the signal up signal up the spinothalamic tract.the spinothalamic tract.


PAIN THRESHOLDPAIN THRESHOLD

•• The threshold for perception of pain is approximately The threshold for perception of pain is approximately the same in all personthe same in all person

•• It is lowered by inflammation (sensitization)It is lowered by inflammation (sensitization)

•• It is raised by local anesthetics, certain lesions of the It is raised by local anesthetics, certain lesions of the nervous system and centrally acting analgesic drugs nervous system and centrally acting analgesic drugs


DIFFERENT TYPES OF PAINDIFFERENT TYPES OF PAIN

•• Acute pain is defined as shortAcute pain is defined as short--term pain or pain with term pain or pain with an easily identifiable causean easily identifiable cause

•• Chronic painChronic pain is medically defined as pain that has is medically defined as pain that has lasted 6 months or longerlasted 6 months or longer

•• Cutaneous pain is caused by injury to the Cutaneous pain is caused by injury to the skinskin or or superficial tissuessuperficial tissues

•• Somatic pain originates from Somatic pain originates from ligamentsligaments, , tendonstendons, , bones, bones, blood vesselsblood vessels, and even , and even nervesnerves themselvesthemselves

•• Visceral pain originates from body organsVisceral pain originates from body organs

•• Phantom limb painPhantom limb pain is the sensation of pain from a is the sensation of pain from a limb that one no longer has limb that one no longer has

•• Neuropathic pain can occur as a result of injury or Neuropathic pain can occur as a result of injury or disease to the nerve tissue itselfdisease to the nerve tissue itself


DIFFERENT PAIN TYPES DIFFERENT PAIN TYPES

•• Skin pain: fast pain is transmitted by ASkin pain: fast pain is transmitted by A--δδ fibers, slow fibers, slow and longerand longer--lasting pain is transmitted by C fiberslasting pain is transmitted by C fibers

•• Deep pain: visceral and Deep pain: visceral and skeletomuscularskeletomuscular structures; structures; sharp, penetrating and burning type (e.g. heartburn sharp, penetrating and burning type (e.g. heartburn and angina pectoris)and angina pectoris)

•• Referred pain: deep pain projects fix site Referred pain: deep pain projects fix site


PAIN INTENSITYPAIN INTENSITY

IntensityIntensity

TimeTime


fast painfast pain

longerlonger--lasting painlasting pain

REFERRED PAINREFERRED PAIN

Diaphragm C4Diaphragm C4

Heart T3Heart T3--44

Esophagus T4Esophagus T4--55

Stomach T6Stomach T6--99

Liver, gallbladder T8Liver, gallbladder T8--1111

Small intestines T10Small intestines T10--L1L1

Large intestines T11Large intestines T11--L1L1Kidney, testicles T10Kidney, testicles T10--L1L1

Urinary bladder T11Urinary bladder T11--L1L1


PAIN DISORDERSPAIN DISORDERS

Peripheral nerve pain (Peripheral nerve pain (neuropathicneuropathic, , neurogenicneurogenic))

–– Pain arises from direct stimulation of nervous tissue, Pain arises from direct stimulation of nervous tissue, pain is due to stimulation of sensitized C fibers pain is due to stimulation of sensitized C fibers

–– Mono and Mono and polyneuropathiespolyneuropathies

–– Plexus lesionPlexus lesion

–– TrigeminalTrigeminal neuralgianeuralgia

–– Root irritationRoot irritation

–– Herpes Herpes zosterzoster

–– DeafferentationDeafferentation painpain

–– Reflex sympathetic Reflex sympathetic distrophydistrophy

–– FibromyalgiaFibromyalgia



Carpal tunnel syndrome (Carpal tunnel syndrome (mononeuropathymononeuropathy))



Carpal tunnel syndromeCarpal tunnel syndrome

•• Due to excessive use of hand Due to excessive use of hand •• DysesthesiasDysesthesias and pain in theand pain in the

fingers fingers •• ParesthesiasParesthesias are worse duringare worse during

the nightthe night•• Pain radiates into the forearmPain radiates into the forearm•• Sensory loss, atrophy, motor Sensory loss, atrophy, motor

weaknessweakness



PolyneuropathyPolyneuropathy: : similar symptoms, similar symptoms, different etiologydifferent etiology


Brachial plexus neuritis (ParsonageBrachial plexus neuritis (Parsonage--Turner syndrome)Turner syndrome)

–– The illness develops abruptly in healthy individuals The illness develops abruptly in healthy individuals

–– Shoulder and neck ache Shoulder and neck ache

–– Pain becomes rapidly more severePain becomes rapidly more severe

–– After a period of 5 to 14 days there is a rapid development After a period of 5 to 14 days there is a rapid development

of muscular weakness, sensory and reflex impairmentof muscular weakness, sensory and reflex impairment

–– AtrophyAtrophy

–– CMV infection, AIDS, Coxsackie virus, vaccinesCMV infection, AIDS, Coxsackie virus, vaccines



LowLow--back painback pain

-- Local pain: Local pain: periosteumperiosteum, capsule of , capsule of apophyseal apophyseal

joints, muscles, ligaments, annulus joints, muscles, ligaments, annulus fibrosusfibrosus

-- Referred pain: projected from the spine to visceraReferred pain: projected from the spine to viscera

-- RadicularRadicular or root pain: distal radiation to the or root pain: distal radiation to the

territory of rootterritory of root

-- Pain secondary to muscle spasmPain secondary to muscle spasm




Disc degenerationDisc degeneration

AbnormalAbnormalNormalNormal


L5 disc: axial viewL5 disc: axial viewS1 root irritationS1 root irritation




Herpes Herpes zosterzoster::•• segmental distribution of rashsegmental distribution of rash•• inflammatory reaction in cranial inflammatory reaction in cranial or spinal sensory ganglia (root)or spinal sensory ganglia (root)•• radicular radicular pain pain •• varicella zoster varicella zoster virusvirus


Central painCentral pain

– Spinal cord lesionSpinal cord lesion: intolerable pain below the level of lesion;: intolerable pain below the level of lesion;

deafferentationdeafferentation of secondary neurons in the posterior horns of secondary neurons in the posterior horns

or of sensory ganglion cells; or of sensory ganglion cells; deafferented deafferented cells become cells become

continuously activecontinuously active

–– Thalamic pain syndromeThalamic pain syndrome ((DDééjerinejerine--RoussyRoussy) and ) and parietal parietal

lobelobe infarctioninfarction ((Schmahmann Schmahmann and and LeiferLeifer), ), lateral lateral medullary medullary

and and pons pons lesionlesion: intractable pain; loss of descending : intractable pain; loss of descending

inhibitory systems and/or altered sensitivity and inhibitory systems and/or altered sensitivity and

hyperactivity of central neuronshyperactivity of central neurons



Primary headachesPrimary headaches

–– Migraine: Migraine: trigeminovascular trigeminovascular headacheheadache

–– Cluster: Cluster: trigeminotrigemino--autonomic headacheautonomic headache

–– Tension headache: contraction of Tension headache: contraction of craniocervicalcraniocervical muscles muscles



Secondary headacheSecondary headache

-- Headaches related to medical diseasesHeadaches related to medical diseases

-- PainPain--sensitive cranial structures: sensitive cranial structures:

1. Skin, 1. Skin, subcutaneussubcutaneus tissue, muscles, tissue, muscles, extracranialextracranial arteries,arteries,

periosteumperiosteum of the skullof the skull

2. Delicate structures of eye, ear, nasal cavities, sinuses2. Delicate structures of eye, ear, nasal cavities, sinuses

3. 3. IntracranialIntracranial venous sinusesvenous sinuses

4. Parts of 4. Parts of duradura and and intracranialintracranial arteriesarteries

5. Optic, 5. Optic, oculomotoroculomotor, , trigeminaltrigeminal, , glossopharyngealglossopharyngeal, , vagusvagus,,

first three cervical nervesfirst three cervical nerves


ANEURYSM RUPTUREANEURYSM RUPTURE


SINUS THROMBOSISSINUS THROMBOSIS


BRAIN TUMORBRAIN TUMOR


THERAPY OF PAINTHERAPY OF PAIN

•• (specific treatment)(specific treatment)•• NonopioidNonopioid analgesicsanalgesics: e.g. Acetylsalicylic acid, : e.g. Acetylsalicylic acid, IndomethacinIndomethacin, ,

NaproxenNaproxen•• Narcotic analgesicsNarcotic analgesics: e.g. Codeine, Morphine, : e.g. Codeine, Morphine, FentanylFentanyl•• AnticonvulsantsAnticonvulsants: e.g. : e.g. CarbamazepineCarbamazepine, , GabapentinGabapentin, , PregabalinPregabalin•• TricyclicTricyclic and SSRI antidepressantsand SSRI antidepressants: e.g. : e.g. AmitriptylinAmitriptylin, , SertalineSertaline•• AnestheticsAnesthetics: e.g. : e.g. LidocaineLidocaine, , MexiletineMexiletine•• Root blocks, epidural injection, ganglion infiltrationRoot blocks, epidural injection, ganglion infiltration•• Ablative surgeryAblative surgery: : rhizotomyrhizotomy, , spinothalamicspinothalamic tractotomytractotomy, bilateral , bilateral cordotomycordotomy, , stereotacticstereotactic surgery on the thalamussurgery on the thalamus

•• Spinal cord stimulationSpinal cord stimulation, , ddeepeep brain stimulationbrain stimulation•• Other treatmentsOther treatments: biofeedback, acupuncture, : biofeedback, acupuncture, transcutaneoustranscutaneous

electrical stimulationelectrical stimulationUniversity of PUniversity of Péécscs, Department of Neurology, Department of Neurology

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Somatic sensation and pain - NeurologyHomePageneurology.pote.hu/neuro/modules/stud/data/061009e.pdf · Free nerve endings -hairy & hairless skin -C fibers ... • Somatic pain originates