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Toronto Notes 2019 Pain Syndromes Neurology N43
Etiology and Pathogenesis
• destructionofthesensoryganglionneurons(e.g.dorsalroot,trigeminal,orgeniculateganglia) secondary to reactivation of herpes zoster infection
Epidemiology
• incidenceinthosewithzosterincreaseswithage(2%in<60yr,19%in>70yr) • riskfactors:olderage,greateracutepain,greaterrashseverity
Prevention
• varicellazostervaccine(Varivax®)inchildhoodreducesincidenceofvaricellazoster
• herpeszostervaccine(Zostavax®)reducesincidencesofshingles,PHN,andotherherpeticsequelae
(currently recommended in Canada for those >60 yr old)
Treatment
• medical:TCA(i.e.amitriptyline),anti-convulsants(i.e.pregabalin,gabapentin),analgesia(i.e.opiates, lidocaine patch), intrathecal methylprednisolone, topical capsaicin
■ early treatment of acute herpes zoster with antivirals (acyclovir; longer-acting famciclovir and valacyclovir more effective)
■ treatment of herpes zoster with corticosteroids DOES NOT decrease PHN
• surgical:spinaltractotomy,dorsalrootentryzonelesion,DBSofthalamus
Painful Diabetic Neuropathy
• seeEndocrinology,E13
Approach
• determineifpainisneuropathicorvascular
• morelikelyneuropathicifpainispresentatrestandimproveswithwalking,painissharp/tingling,
more in feet → calves
Treatment
• LevelA:pregabalin
• LevelB:venlafaxine,duloxetine,amitriptyline,gabapentin,valproate,rarelyopioids,capsaicin
Complex Regional Pain Syndromes
Clinical Features
• presenceofaninitiatingnoxiousevent(MI,stroke)
• continuingpain,allodynia,orhyperalgesiawithpaindisproportionatetoincitingevent
• evidenceduringthecourseofsymptomsofedema,changesinskinbloodfloworabnormalvasomotor
activity
• absenceofconditionsthatwouldotherwiseaccountfordegreeofpainanddysfunction
• otherfeaturescanincludeedema,osteoporosis,hyperhidrosis,hairloss,fascialthickening
Classification
• CRPStypeI(reflexsympatheticdystrophy):minorinjuriesoflimborlesionsinremotebodyareas precede onset of symptoms
• CRPStypeII(causalgia):injuryofperipheralnervesprecedestheonsetofsymptoms
Investigations
• trialofdifferentialneuralblockademaybehelpfulindiagnosis • autonomictesting(evidenceofsympatheticdysfunction)
• bonescan,plainradiography,MRI
Prevention
• earlymobilizationafterinjury/infarction
Treatment
• goaloftreatmentistofacilitatefunction
• conservativetreatment:education,supportgroups,PT,OT,smokingcessation
• medical:topicalcapsaicin;TCA;NSAID;tenderpointinjectionswithcorticosteroid/lidocaine;
gabapentin/pregabalin/lamotrigine; calcitonin or bisphosphonates; oral corticosteroids • surgical:paravertebralsympatheticganglionblockade
• refertopainmanagementclinic