CNS infections

Acute bacterial meningitis agents <3 mths vs more than 3 mths

• <3 months : GBS, E.Coli, Listeria monocyogenes

• >3 months : N. Meningitidis, S. Pneumonia, H. Influenza

Acute bacterial meningitis pathogenesis

Bacteria from nasopharynx, transmitted via aerosol, droplets and contact. then spread via:-

• Haematogenous spread (common) : from tracts (resp, gi, gu) then invade into bloodstream then to subarachnoid space

• contiguous spread : septic foci in head, osteomyelitis, otitis media etc

• direct implantation : trauma/ fractured skull and neurological procedures

Acute bacterial meningitis clinical features

• fever, headache, n&v

• pyerxia, rash in some (meningococcal), meningeal irritability

• neurological sequele : impaired mental status, increased ico, hearing loss

Meningeal irritability by what measures (3)

• nuchal rigidity : neck stiffness

• kernig’s sign : resistance of knee extension when hip flexed

• Brudzinski’s sign : passive neck flexion leads to knee flexion

Meningococcal bacteraemia what

• erythematous macule → petechiae → purpura/ecchymosis

• use glass test → non blanching petechiae

nb : not skin haemorrhage but thrombosis of small vessels in skin resulting in ischaemia

Meningitis investigations

• fbc, u&e, glucose

• blood cultures : before antimicrobials

• CSF

• EDTA sample for PCR

• CT brain before Lumbar puncture (prevent brain herniation)

Treatment for acute bacterial meningitis

• <3 months : amoxicillin + cefotaxime

• >3 months : vancomycin + 3rd gen cephalosporin (+ amox if old/ immunocompromised)

• steroid such as iv dexamethasone to reduce inflammation esp s. pneumoniae and H. influenza

Meningococcal meningitis (4 wo prevention)

• high incidence in ya

• sporadic / oitbreak caused by 6 serotypes (a,b,c,w,x,y)

• risk factor in immunideficiency, asplenia, complement deficiency)

• short incubation, tx by benzylpenicillin + amox + cefotaxime

nb complement deficiency (c3 and terminal complement)

Meningococcal meningitis control and prevention

• chemoprophylaxis : ciprofloxacim, rifampicim, ceftriaxone

• vaccine , men A,B,C, ACWYB

• isolation

• contact tracing

H Influenza meningitis

• Usually from capsular type B

• chemoprophylaxis and Hib vaccine

Pneumococcal meningitis

• more susceptible in asplenia, alcohol use, DM

• tx by amox + 3rd gen cephalosporin

• prevention by vaccines (PPV23, PCV) but no chemoprophylaxis

Mycobacterium tuberculosis CNS imfection (4)

• meningitis

• tuberculoma (granuloma in brain/spinal cord)

• spinal arachnoiditis

• transverse myelitis

Pathogenesis cns (6)

• M tuberculosis enters lungs via airborne transmission (deoplet inhalation

• Phagocytose by alveolar macrophage/ in regional ln

• spread haematogenously (bacteraemia)

• go brain, become supepyndymal foci (rich foci)

• imcrease suze causing rupture in subarachnoid space

• TB meningitis

Clinical manifestation of TB meningitis

• exudate at base of brain : cranial nerve palsies, hydrocephalus

• Vasculitis : occlusion, stroke

• encephalitis : increased icp

how to distinguish bacterial meningitis and tb meningitis

• subacute presentation

• neurological sx

• presence ofcranial nerve palsies

Tb meningitis disease stages

• stage i : alert and orient wo focal neurological sx

• stage ii : concious w inattention, confusion and lethargy

• stage iii : advanced illness w delirium, stupor, coma

TB meningitis diagnostics

• CSF : afb pn ziehl nielstain stain, culture positive

• pcr

• ct/mri

Viral meningitis causative agent

• eneterovirus

• echovirus

• coxsackie

• HSV, ebv

• measles, mumps

CSF findings in bacterial, viral, tb meningitis

• Cell coint : bacteria alot (100-10000), viral and tb lesser than (10-1000)

• protein (g/l) : bacterial >1, viral 0.5-1 but tb most, 1-5

• blood glucose : bacterial and tb <50% but viral >50%

Encephalitis causes

• bacterial : tb, borrelia

• fungal : cryptococcus neoformans

• protozal : toxoplasma, olasmodium

• viral : hsv, enetero, arbo, mmr

Encephalitis vs meningitis

• meningitis have intact cerebral function

• encephalitis exhibit cognitive dysfunctiom, behavioural change, altered concious

viral encephalitis dx and tx

• blood cultures : lymphocytic, elevated ish protein but nirmal glucose

• serology / pcr : hsv, ebv etc

• mri/eeg . focal slowing, spiking

• tx by acyclovir before results

non hsv encephalitis pathogens (3)

• arbovirus : mosquito or tick borne

• dengue virus : aedes mosquitoes + break bone fever

• japanese encephalitis virus : pigs, wading

Brain abscess pathogenesis (3)

• contiguous focus of infection : otitis media, mastoiditis, sinusitis (direct extension)

• haematogenous spread from distant focus : ie, dental procedures, pyogenic lung disease (muktiole abcess)

• trauma : penetrating head injury

Brain abcess pathogens

• streptococci (eg viridians)

• anaerobes

• eneterobacteriaceae (eg klebsiella pneumonia, pseudomonas)

• s. aureus

• fungi, mycoplasma

Brain abcess sx

depends on location of abcess

• temporal lobe : memory defects, aphasia

• frontal lobe : altered personality, drowsiness

• cerebellum : ataxia

brain abcess dx

• ct/mri : lesion, oedema, herniations

• blood sample

• pus sample

nb pus sample

Brain abcess tx

• aspiration

• craniotomy and excision

• antimicrobial : fluclox/vanco, cefotaxime, metronidazole

N. meningitidis microbiology

• gram negative diplococci

• aerobic

• oxidase positive

N meningitidis virulence factors (5)

• capsule : anti phagocytic and anti complement

• pili

• IgA protease

• lipooligosaccharide : endotoxin

• outer membrane proteins

invasive meningococcal disease sx (5)

• initially general sx

• leg pain, cold hands and feet, abnormal skin colour

• meningococcal rash : petechial, non blanching rash from trunk and lower limb → progress to purpura and ecchymoses

• meningeal irritability

• adrenal haemorrhage (waterhouse friderichsen syndrome)

investigation of invasive meninggococcal disease

• csf in meningococcal meningitis : gram negative diplococci

• culture in chocolate agar for translucent grey white colonies

• pcr

Borrelia

• spirochate

• dx by silver stain under light microscopy, immunofluorescence

• cause lyme disease, louse borne relapsing fever, tickborne relapsing fever

lyme disease

• caused by b burgdorgeri (less commonly b mayonii, afzelii, garinii)

• bimodal, distribution (old and young

• transmitted by bites of infected ixodes tick

• 3 stages : early localised, early disseminated, late disseminated

Early localised disease of lyme disease

• erythema migrants

• red macule or papule w central clearing

• at axillar, groin, popliteal fossa

Early disseminated disease (5)

• skin : disseminated erythema migrans

• neurological : lymphocytic meningitis, CN palsy

• cardiac : av block, myocarditis

• msk : myalgia, arthralgia

• ocular : conjunctivutis, uveitis

late disseminated disease of lyme(3)

• msk : arthritis, athralgia

• neurological : encephalopathy, peripheral neuropathy

• skin : acrodermatitis chronica atrophicans

dx of lyme disease

• suspect if : pt risk of exposure to ticks causing lyme (travel) + clinical manifestation

• erythema nigrans on clinical grounds

• early andlate disseminated : eia followed by western blot or eia followed by eia

tx of lyme disease for each stage

• erythema migrans : doxy (10/7), amox (14/7)

• early disseminated : doxy (14), ceftriaxone

lyme disease prevention

• environmental measures

• ppe

• post exposure prophylaxis : doxy (nb may get fatigue, myalgia, brain fog)

Picornaviridae examples and structure

• polio, coxsackie virus a&b, rhinivirus

• no envelope : resistant to acid, bile, etc

• VP1 : main antigenic site and receptor binding (serotyped based on this)

• positive sense RNA wo rna pokymerase : high mutation rate

picornaviridae pathogenesis

• entry by faecal oral, replicate at pharynx and gut lymphoid tissue

• spread to regional ln and reticuloendothelial system

• major viraemia : seeds to target organs : meninges, cns etc

• cross bbb or from axonal up motor neurones

what is aseptic meningitis and causative agents

• meningeal inflammation w sterile csf

• caused by enterovirus b (coxsackie b and echovirus)

• typically self limiting

meningitis vs encephalitis

• meningitis is inflammation of meninges, have non cerebral function sx (headache, photophobia)

• encephalitis : inflammation of brain parenchyma causing altered mental state

sx and tx for enterivirus in neinates

• fulminent disseminated illness

• meningitis, sepsis, hepatitis w coagulopathy, myocarditis

• usually due to coxsackie b and echovirus 11

• tx by IVIG ±antivirals (trials)

HFMD cns pathogenesis

• fever w oral ulcers & vesicles on hand and feet

• cns involvement of cns : myoclonuc jerk, ataxia, tremor

• autonomic dysregulation : tachycardia, htn, sweating

• collapse

poliomyelitis (what, sx, prevention)

• by polio virus

• reach spinal cord of anterior horn motor neurones

• lower motor neurone lesion

• sx : assymetric ,flaccid but no bulbar polio (most notably cant breathe

• prevent by polio vaccine

polio vaccine types and pros/cons

• ipv ,: killed virus but less immunity and costlier

• opv : oral live attenuated virus w better immunity but may cause VAPP(vaccine attenuated paralytic polio) or cVDPV (circulating vaccine derived polio virus)

Acute flaccid myelitis (what, sx, tx)

• polio like illness w acute flacid limb weakness w spinal cord grey matter lesions

• due to ev d68

• often preceding a respiratory illness

• tx supportive, rehab but no antivirals approves