CNSinfections2BrainAbscess/subduralempyema

Sources/tablesandfigures:HarrisonsInfectiousdiseases2nd ed Ch31

OxfordHandbookofInfectiousdiseasesandmicrobiology2nd ed Ch19

Brainabscess

• Afocal(notalloverthebrain),suppurative(pusforming)intracerebralinfection.• Thatbeginsasalocalareaofcerebritis whichdevelopsintoacollectionofpussurroundedbyawell-vascularizedcapsule(abscess).• Ifbacteriaremainunfocalizedtheresultingsyndromeiscalledcerebritisonly.• Entryofbacteriatothebraincaneitherbeadirectspreadfrom:àcontiguousareasintheskull(closeanatomicsite:ear,sinus,teeth,orpost-neurosurgery)

à seedingfromthebloodfromanotherpointofinfection,furtheranatomicsites(e.g.endocarditis,lung,abdomen,skin).

https://www.mypacs.net/repos/mpv3_repo/viz/full/0/40/230/42179420.jpg

https://3.bp.blogspot.com/-GznpxCOxk4w/WUjwLUc79DI/AAAAAAAAnOA/yuNPnsWCSlUoBUa2iHDGXygPhY6HYsnuQCLcBGAs/s1600/4-2.jpg

Epidemiology

• Althoughbrainabscessesareuncommonitishoweverasevere,disease(incidenceof∼0.3–1.3:100,000personsperyear).• Predisposingconditionsareusuallypresentthatpushpatientsdefencesandcauseabscessformationinthebrain.• Contiguoussiteinfectionsoftheskull:otitismedia,mastoiditis,paranasalsinusitis,dentalinfections,pyogenicinfectionsinthechestorotherbodysites,penetratingheadtraumaorneurosurgicalprocedures areconsideredthemajorpredisposingfactors(morethanhematologicspread)• Brainabscessisseenmoreinmalesintheagegroupof30-40 years.

• Casefatalityratesrangefrom0%to 24%(usuallylargediscrepancyinnumberslikethisindicatediscrepancyinlevelofcare).

Pathogensinvolved

• Mostcommonlyasingleorganismisinvolved,lesscommonly(23%<)polymicrobial,withpredilectiontotheFRONTALlobe.

• However,sourcealsoindicatessite(ear-temporallobe– seepathogensinvolvedwithsiteonnextslides).

• Leftsided>rightside• Usuallyduetotraumaperhapsbeingmoreontheleftduetohandedness

• Pathogensinvolvedaremostlyaerobes(stertococci)>anaerobes(bacteroides,peptostreptococcus)• Thisisduetothefactthatthebrainishighlyperfusedtissue(lotsofoxygen),anaerobeswillrequirepoorcirculationtosucceedinearlyinfection•à thusanaerobesarecommonlyseeninpolymicrobial abscesses-anywhere- theywaitforaerobestocreatefavorableconditionsandthentheystartgrowing.• Afacultativeanaerobelikestrepandlesssostaphcanovercometheoxygenrequirementsmorerequirment

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4212419/table/table1-1941874414540684/

Proteusesp,usuallynonfecalorigin

Inimmunocompetent

• Theencounteredpathogensare:Streptococci.- Viridans (40%)groupStreptococciisthedominantpathogeninthisgroup.- Anaerobic- peptostreptococcus usuallyseeninimmune-competentpatients- GroupA,S.pnuemoniae arerarley seen(immunecompetentpatientusuallyhasencounteredtheseorganismsandhaveantibodiesformed)

Althoughstreptococcihavevirulencefactorswhichenabledirectspreadbutproximityisthemostdominantfactorasseenbypathogenmakeupandusualnicheoccupied(viridansgroup,whichismostcommonlyseenintheskullandespeciallythepharynx-)thosethatdependonevadingimmunesystemintheblood–S.pneumoniae- arerarleyseeninsidethebrain,howeverthesearecommoninmeningitis(>hematogenous route).

Immunecompetentpatient,othercauses

- Enterobacteriaceae [Proteus,E.coli,Klebsiella.(25%)]- Anaerobes[Bacteroides spp.Fusobacterium spp.(30%)],- Staphylococci(10%).

Inimmunocompromised

(typicallyHIVinfection,cancer,orimmunosuppressivedrugs):

-Nocardia-Toxoplasmagondii,-Aspergillus (moldmc)-Candida-Cryptococcusneoformans (yeast,aerobe).Typicallyifyouseemolds,yeastsorsomeparasitesintissuesthatarenottypicallyexposedtothem(skin),youmustaskyourself,whydidtheimmunesystemfailforsolongtomountaneffectiveimmuneresponseagainstalessaggressive,typicallyslowergrowingorganisms?à Anotherfactorisemergingdrugresistanceintheseorganisms,thatisslowlymakingthemrivalbacterialinfections.

Etiology

• 1- fromacontiguouscranialsiteofinfection,suchasparanasalsinusitis,otitismedia,mastoiditis,ordentalinfection(mostcommon~50%)• 2- followingheadtraumaoraneurosurgicalprocedure(withdirectspread,accountfor25- 50%)• 3- asaresultofhematogenousspreadfromaremotesiteofinfection(25%).• Inupto25%ofcases,noobviousprimarysourceofinfectionisapparent(cryptogenicbrainabscess).

Hematogenousabscesses

• Theseareoftenmultiple(duetoseeding),thusmultipleabscessesoften(50%)aretracedtoahematogenousorigin,andhavecertaincharacteristics:• -Theseabscesseshaveapatternofsproutinginthedistributionofthemiddlecerebralartery(posterior,frontal,parietallobes).• -Theyareoftenfoundatthejunctionofthewhiteandgreymatters• -Theyareoftenpoorlyencapsulated.• Thepathogenspresentintheseabscecces dependonthesourceofinfection(cardiac,skin..etc)• Typicallycausedbypneumoniaandendocarditis

Clinicalfeatures

• Surprisingly,theinitialclinicalpresentation-earlycerebritis- isNONSPECIFIC!Thisresultsindelayeddiagnosis.(thesignsandsymptomsatfirst don’tpointtobrainlesion)• Theclassicclinicaltriadofheadache,fever,andafocalneurologicdeficitispresentinlessthan50%ofpatients.• Ofthesesymptoms,headacheisthemostcommon(70%)andmaybelocalizedtothesideoftheabscess.Feverinabout50%,whereasfocalneurologicaldeficits(50%),seizures(25%),andneckstiffness(15%)areseen.

• Nausea,vomiting,cranialnervepalsies,andpapilledemaindicateraisedICP.• Changesinmentalstatussimilartomeningitisisassociatedwithhighermortality(lethargy,coma).• Symptomsprogressfromnonspecificsymptomstomorespecificorvariablesymptomsprogressesinavariablemanner,whichcanrangeintimefromhourstodaystoevenweeks!,however,mostpatientspresentin11-12daysfromonsetofsymptoms.

Diagnosis

• •Imaging• AnurgentCTscanwithcontrastshouldbedonetoconfirmtheDx.• Earlycerebritis (beforefocalabscessformation)appearsasanareaoflowdensity,whichdoesnotenhancewithcontrast.• AsthelesionprogressesandenlargesacapsuleisformedthatenhanceswithcontrastCT• MRIismoresensitive(itisnotdoneinfirstlinemanagementassymptomsarenonspecificandnoindicationforMRIispresent),MRIcanvisualizethebrainstembetter.• •inthepresenceoffocalsymptomsorsignsLUMBARPUNCTUREISCONTRAINDICATEDàriskofbrainstemherniation.• Ifbacterialmeningitisissuspected,bloodculturesshouldbetakenandanLPdeferred untilamasslesionisexcludedbyCT/MRI scan(orlookatthefundusforpapilledema)

https://www.researchgate.net/publication/288507711_Imaging_Aspects_of_Pyogenic_Infections_of_the_Central_Nervous_System/figures?lo=1

https://clinicalgate.com/wp-content/uploads/2015/03/B9781416053163000447_f043-001-9781416053163.jpg

https://www.mypacs.net/repos/mpv3_repo/viz/full/0/40/230/42179420.jpg

Dx.Cont.

• Culture—• Oncethelesionsareidentified,CTguidedsurgicalaspirationisperformed.• AspirationsamplesareculturedforbacterialgrowthaswellaslookingforTBandfungalcultures.• 16SrRNA PCRmaybehelpfulinculture-negativecases.• (16sribosomalRNAofthe30ssubunit,usedforphylogeneticanalysisduetolowevolutionrateandcanbeusedtodistinguishbetweenspecieswithhighspecificity)• Bloodculturesshouldbeperformedaswell(septicworkup/should/wouldhavebeendone)• •incasesofcerebraltoxoplasmosisandneurocysticercosis (Neurocysticercosis serologyisused).

• MostaccuratestepistoperformagramstainonCTguidedaspirate(willshoworganismasitispuscollection!)• Aerobic,anaerobicbacterialculturesandmycobacterialandfungalculturesshouldbedoneonthesample(eachhasaspecificmediumandgrowthconditions).• Upto10%ofpatientswillalsohavepositivebloodcultures(80-90%inListeria).• AdditionallaboratorystudiesmayprovidecluestothediagnosisofbrainabscessinpatientswithaCNSmasslesion:• - 50%showperipheralleukocytosis• - 60%anelevatedESR• - 80%anelevatedC-reactiveprotein.

Treatment

• Dependsonthetypeofabscess:• -Forbrainabscessarisingfromlocalskullinfection(dental,sinus,ear)• à empiricaltherapywithceftriaxone2gbd(2/day)IVandmetronidazole500mgtds (3/day)IVisappropriate.• -Forbrainabscessesarisingfromhaematogenous spread(suchasendocarditis),• à vancomycin15–20mg/kg/doseevery8–12h(upto2g/dose)canbeaddedtotheregimenabove.• -Forbrainabscessesoccurringpost-neurosurgery• à vancomycin15–20mg/kg/doseevery8–12h(upto2g/dose)+ceftazidime2gtds IVormeropenem2gtds IVisappropriate.

• Oncecultureresultsareavailable(specificpathogenisidentified):•àsensitivitytestisdoneonthepathogenandappropriateantimicrobialtherapyisgivenfor2–4weeksIV,followedby2–4weeksPO.• Patientswithmultiplelesionsormultiloculated lesionsorthosewhoareimmunocompromisedmayrequirelongercourses.• •Adjunctivecorticosteroidsshouldbegiventopatientswithsignificantedemaandmasseffect.

Subduralempyema

• Definedasacollectionofpusinthespacebetweentheduraandthearachnoidmembranes

https://static-content.springer.com/esm/art%3A10.1186%2F1752-1947-8-282/MediaObjects/13256_2014_2904_MOESM4_ESM.jpeg

https://www.epainassist.com/brain/subdural-empyema

Epidemiology

• Morerarethanabscess=15–20%oflocalized/focalintracranialinfections.• Riskfactors:• Similartobrainabscess,localroutefromsinusitis,otitismedia,mastoiditis,skulltrauma,neurosurgery,• Additionallocalriskfactions:infectionofpreexistingsubduralhaematoma,nasalsurgery,ethmoidectomy,orpolypectomy(fromnasopharynx).• A complicationofmeningitisininfants(MRIfrompreviouslecture).

Etiology

• Organismsusuallyseenarealsosimilar:

• Streptococci,staphylococci,aerobicGram–ve bacilli,andanaerobes.

• Polymicrobialinfectionsarecommon.(abscesssingleorganismmore-asitismoredistance,lessdistanceinempyema=morebacteriafound)

• Trauma/procedurerelatedempyemaisusuallycausedbystaphylococcioraerobicGram-negativebacilli.

Clinicalfeatures

• Acute onsetfever(bacteria/infection)• Headache-masseffect,thusmaybelocalized• andvomiting(raisedintracranialpressure)• Notethesesymptoms(withoutfeveralsoareseeninsubduralhematoma)• Additionally:alteredmentalstate(disorientation,drowsiness,coma),andfocalneurologicalsigns(hemiparesis,cranialnervepalsies,dysphasia,homonymoushemianopia,cerebellarsigns)theseindicatedamagetounderlyingbraintissue.

• 80%ofpatientshavemeningealsymptoms/signs.• Seizurescanoccurinalmost50%ofcases.• TheremayberapidneurologicaldeteriorationwithsignsofraisedICPandcerebralherniation(emergency).• Complicationsare:• septicvenousthrombosis(proximitytoveins+sluggishbloodmovementaroundtheempyemasite)• Andcanprogresstononfocal (cerebritis)orfocalcerebralabscess.• Ininfantswithsubduralempyema,persistentfever,declineinneurologicalstatus,andseizuresareseen.• Spinalepiduralabscesspresentswithradicularpainandsignsofspinalcordcompression

Diagnosis

• Considerthediagnosisinanypatientwithmeningism andfocalneurologicalsigns.• AGAINLPiscontraindicated.• CTorMRIbrainscanshowsacrescenticorellipticalareaofhypodensity withcontrastenhancement.• MRIismoresensitivethan CT.

Management

• Subduralempyemaisanemergencyà immediatesurgicalmanagement.• Asinabscess,mustsendsamplesforurgentmicroscopyandculture.• CommenceempiricIVantibioticsimmediatelyafteraspiration.• Thiswouldbebasedonthelikelyinfectingorganisms(ceftriaxoneandmetronidazole).• Vancomycinshouldbeaddedforsuspectedstaphylococcalinfection(especiallywithhistoryofneurosurgicalprocedures).• Oneidentificationandsensitivityareready=specifictreatmenttocultureresults.• Asinallcasesofneurologicalinfections:Prognosisisbetterifpatientisconsciousatpresentation(>90%forpatientswhoareawake/alert)

Epiduralabscess• collectionofpusbetweentheduramaterandtheoverlyingskullorvertebralcolumn.Maybecomplicatedbysubduralempyema.

http://accessmedicine.mhmedical.com/data/books/harr/harr_c381f007.jpghttp://epmonthly.com/wp-content/uploads/2016/04/SpinalAb2.png

Epidemiology

• Theepidemiologyofcranialepiduralabscessissimilartothatofsubduralempyema.• However,spinalepiduralabscessusuallyoccursduetohaematogenous spreadorduetoprogressionofvertebralosteomyelitis(boneinfection).• Riskfactors:• -bacteraemia• -DM• -skininfection(hastopenetrateonelayer-bone-)• spinalprocedures(surgery/epiduralmedication/trauma/LP).

Etiology

• Similarmicrobiologyspectrumthatisseeninsubduralempyema• S. aureusisthecommonestcauseofspinalepiduralabscess.• Othersincludeaerobicandanaerobicstreptococci,aerobicGram-negativebacilli(e.g.E. coliandP. aeruginosa);5–10%arepolymicrobial.• UnusualcausesincludeNocardia,MTB,and fungi(endemicorimmunocpmpromised).

Clinicalfeatures

• Thepresentationmaybenonsepecific,withlocalinfectionmaskingthesymptoms(bytheprimaryfocusofinfection,e.g.sinusitis,otitismedia).• Headacheiscommon,andfocalneurologicalsignsandseizureseventuallydevelop,followedbysignsofraised ICP.

•Spinalepiduralabscesscanbeacuteorchronicdependingonsource:àhours/dayswithhaematogenous spreadàweek/monthswithvertebralosteomyelitis.Painisthecommonestsymptom(70–90%),followedbyfever(60–70%).Stagesarerelatedtoprogressionoftheabscessanditseffectonthespinalnerveroots,theefourclinicalstages: (1) backpainandtendernessà (2)nerverootpainà (3)spinalcordsymptoms(motororsensory,sphincterdysfunctioninlowerspine)à (4)paralysis.

Diagnosis

• Gadolinium-enhancedMRIisthegoldstandardtoolforDx.

Management

• AswithallabscessesthebasicRxisdrainageandAbx.• à Cranialepiduralabscess—surgicaldrainageandantibiotics(for3–6weeks).• à Spinalepiduralabscess—surgicaldecompression(laminectomy)andantibiotics.• Empiricaltherapyshouldcoverstaphylococci(e.g.vancomyin)thisisduetothecloseproximitytoskin,staphlycocci arecommon.• AlsoaerobicGram-negativebacilli(e.g.ceftriaxone,ceftazidime,ormeropenem).• Theoutcomeofspinalepiduralabscessdependsonthelevelofneurologicaldeficitbeforedecompression.

CSFshuntinfections

• Infectionisacommoncomplicationofneurosurgicalproceduresthatareusedtotreathydrocephalus• Thesecanoccurinupto75%ofcases!• Mosttypeofdevicescanbeinfected,theseareforeignbodies,pathogensareacommoncomplicationforanyFBintroducedintothebody,moresointheCNS,whereimmunitymybelessquicktorespond.• Seeninventricularshunts,Ommayma drains..etc• Someclassifytheshuntinfectionsasinternal(CSFabnormalities)orexternal(softtissueabnormalities).

Etiology

• Asyoumightexpect,SKINfloraistypicalculprit• •S. epidermidisistheMCC.• •S. aureus,including MRSA.• •Streptococci,enterococci.• •P. acnes(Propionbacterium acnes,involvedin…acne,theskincondotion)• •Gram-negativeorganisms,includingP. aeruginosa.• •Mycobacteria.• •Fungi.

Pathogenesis

• Thepathogenesiscanbepredictedfromthemicrobiologyoftheseinfections:

• Typically•à contamination(attimeofimplantationofthedevice)•à externalization(erosionofshuntthroughtheskin)•à retrograde(perforationofVPshuntthroughthebowel)•à haematogenous (rare).

Clinicalfeatures

• Dependonsiteofinfection,ageofthepatient,andwhethertheshuntfailedandsignsofincreaseICPisevident• Symptoms:• -fever,headachesignsofinfection• nausea,vomiting(ICPsigns)neckstiffness(meningealsigns)andimpairedconscious level(latesign)

Laboratorydiagnosis

• directaspirationoftheshuntandCSFexamination• CSFsamplesshouldbetakenforurgentmicroscopy,culture,protein,andglucose• .BloodtestsandculturesinconjunctionwithCSFanalysis(ESR,leukocytes,CRP..etc)• BCs—90%positivewithVenticuo Atrialshuntinfections.• •CT/MRI• •CXRifVAorventriculopleural shunt.• •Abdominalultrasound/CTscanifabdominalsymptoms/signsandVPorlumbarperitoneal shunt.•ConsiderechocardiogramifVA shunt.

https://ars.els-cdn.com/content/image/1-s2.0-S0887217116000044-gr1.jpg

Management

• RemovalandreplacementofshuntonceinfectionhasclearedandCSFissterileagain(withAbxtreatment)• Abx• Empiricantibiotictherapyshouldinclude:vancomycinIVandintrathecally,IVmeropenemwithabdominalsymptomsorG-ve seeninCSF• Specifictherapyoncecultureandsensitivityisback