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CNS Infections. Path. Four principal routes via which infections may enter the nervous system. Hematogenous spread – arterial circulation, retrograde venous circulation Direct implantation – traumatic, possibly iatrogenic

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CNS Infections

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four principal routes via which infections may enter the nervous system
Four principal routes via which infections may enter the nervous system
  • Hematogenous spread – arterial circulation, retrograde venous circulation
  • Direct implantation – traumatic, possibly iatrogenic
  • Local extension – secondary to an established infection in an air sinus – mastoid or frontal, infected tooth, surgical site
  • Peripheral nervous system – certain viruses – rabies, herpes zoster
meningitis definition and classification
Meningitis – definition and classification
  • Inflammatory process of the leptomeninges and CSF within the subarachnoid space
  • Classified into
    • Acute pyogenic
    • Aspetic (usually acute viral)
    • Chronic (TB, spirochetal, cryptococcal)
acute pyogenic meningitis causative agents clinical
Acute pyogenic meningitis – causative agents, clinical
  • Causative agent vary with age of patient
    • Neonates – E coli, group B streptococci
    • Adolescents/young adults – neisseriameningitidis
    • Elderly – strep pneumonia, listeriamonocytogenes
    • Immunisation has drastically reduced haemophilusinfluenza
    • Immunosuppressed patient – klebsiella, anaerobic organisms
  • Clinical – systemic signs, headache, photophobia, irritability, clouding of consciousness, neck stiffness
acute pyogenic meningitis lp associated syndromes
Acute pyogenic meningitis – LP, associated syndromes
  • Lumbar puncture – frankly purulent CSF, under increased pressure, many as 90,000 neutrophils/mm^3, raised protein level, markedly reduced glucose content
  • Waterhouse-Friderichsensyndrome – results from meningitis associated septicaemia with hemorrhagic infarction of the adrenal glands and cutaneouspetechiae
acute pyogenic meningitis morphology
Acute pyogenic meningitis – morphology
  • Acute – exudates evident within the leptopmeninges over the surface of the brain
  • Vessels are engorged and stand out prominently
  • Location of exudates varies
    • H.influenazae – basal
    • Pneumococcal meningitis – densest over cerebral convexities near the sagittal sinus
    • Fulminant meningitis – inflammation may extend to the ventricles – ventriculitis
  • Micro
    • Neutrophils fill the subarachnoid space in severely affected areas, predominantly around leptomeningeal blood vessels in less severe cases
    • Focal cerebritis – infiltration of inflammatory cells into the substance of the brain (go through the leptomeningeal veins)
  • Leptomeningeal fibrosis and hydrocephalus follow pyogenic meningitis
  • Chronic adhesive arachnoiditis – large quantities of capsular polysaccharide of the organism produce a particularly gelatinous exudates that encourages arachnoid fibrosis
acute aseptic meningitis clinical lp causative agents
Acute aseptic meningitis – clinical, LP, causative agents
  • Clinical - meingealirritation, fever, alterations of consciousness of relatively acute onset
  • Usually viral
  • Clinical course less fulminant, usually self limiting, treated symptomatically
  • CSF – lymphocytic pleocytosis, protein elevation is only moderate, sugar content is nearly always normal
  • 70% pathogen can be identified – commonly enterovirus
    • Echovirus, coxsackievirus, nonparalytic poliomyelitis – up to 80% of cases
brain abscesses path predisposing conditions organisms
Brain abscesses – path, predisposing conditions, organisms
  • Arise from
    • Direct implantation of organisms
    • Local extension from adjacent foci – mastoiditis, paranasal sinusitis
    • Hematogenous spread – primary site in heart, lungs, distal bones or after tooth extraction
  • Predisposing conditions
    • Acute bacterial endocarditis (multiple abscesses), cyanotic congenital heart disease (R to F shunt), chronic pulmonary sepsis (bronchiectasis)
  • Streptococci, staphylococci most common organisms in non-immunosuppressed
brain abscesses morphology
Brain abscesses – morphology
  • Macro – discrete lesions with central liquefactive necrosis, surrounding fibrous capsule, oedema
  • Most common brain regions in descending order – frontal lobe, parietal lobe, cerebellum
  • Micro – exuberant granulation tissue, neovascularisation around the necoriss that is responsible for marked vasogenic oedema
  • Collagen produced by fibroblasts from walls of vessels, outside fibrous capsule zone of reactive gliosis with numerous gemistocyticastrocytes
brain abscesses clinical csf prognosis
Brain abscesses – clinical, CSF, prognosis
  • Destructive lesions – patients present progressive focal deficits, signs of raised intracrnail pressure
  • CSF – under increased pressure, white cell count raised, protein raised, sugar content is normal
  • Source of infection may be apparent
  • Increased intracranial pressure and herniation may be fatal
  • Abscess rupture lead to ventriculitis, meiningitis, venous sinus thrombosis
  • Surgery, antibiotics, otherwise high mortality reduced to 10%
subdural empyema path clinical symptoms csf treatment
Subdural empyema – Path, clinical, symptoms, CSF, treatment
  • Bacterial/fungal infection of skull bones or air sinuses can spread to subdural space – empyema
  • Arachnoid, subarachnoid is unaffected, subdural empyema can produce a mass effect
  • Thrombophlebitis may develop in the bridging veins that cross the subdural space
    • Venous occlusions and infarction
  • Symptoms – source of infection related, febrile, headache, neck stiffness, focal neurologic signs, lethargy, coma
  • CSF similar to abscess
  • Treatment – surgical drainage, resolution occurs from the dural side, if complete -> thickened dura may be the only residual finding
chronic bacterial meningoencepahlitis tb csf symptoms complications related infecitons
Chronic bacterial meningoencepahlitis – TB – CSF, symptoms, complications, related infecitons
  • CSF – moderate pleocytosis (mononuclear cells), protein level is elevated strikingly so, glucose moderately reduced or normal
  • Symptoms – headache, malaise, mental confusion, vomiting
    • Most serious complication – arachnoid fibrosis – hydrocephalus
      • Obliterative endarteritis – arterial occlusion, infarction of underlying brain
      • Spinal roots may also be affected
  • AIDS patients also at risk of infection with M. avium-intracellulare – setting of disseminated infection
    • Lesion – confluent sheets of macrophages filled with organisms, minimal granulomatous reaction
chronic bacterial meningoencepahlitis tb morphology
Chronic bacterial meningoencepahlitis – TB – morphology
  • Morphology
    • Macro
      • Subarachnoid space contains a gelatinous or fibrinous exudates, most often at the base of the brain -> oliterateing the cisterns and encasing cranial nerves
    • Meningoencephalitis – most common pattern of involvement
    • Micro – mixture of lymphocytes, plasma cells, macrophages
      • Florid cases – well formed granulomas, caseous necrosis, giant cells
      • Arteries in subarachnoid space
        • Obliterative endarteritis
        • Inflammatory infiltrates in their walls, marked intimal thickening
    • Organisms often seen with acid-fast stains
    • Infection can spread to the choroid plexus and ependymal surface- through CSF
    • Long standing duration – dense, fibrous adhesive arachnoiditis
    • Tuberculoma – single or multiple well circumscribed intraparenchymal mass
      • May be several cm in diameter – mass effect
      • Micro – central core caseous necrosis surrounded by typical tuberculousgranulomatous reaction, calcification may occur in inactive lesions
neurosyphillis major forms path morphology
Neurosyphillis – major forms –path/morphology
  • Meningovascularneurosyphilis
      • Chronic meningitis involving the base of the brain, cerebral convexities, spinal leptomeninges
      • Obliterative endarteritis (Huebner arteritis)
      • Perivascular inflammation, plasma cells, lypmhocytes
  • Paretic neurosyphilis
      • Insidious but progressive loss of mental and physical functions with mood laterations terminating in severe dementia
      • Micro – lesions associated with parenchymal damage in the cerebral cortex
        • Loss of neurons, proliferations of microglia, gliosis, riondepositsi -> Prussian blue stain
        • Granular ependymitis – proliferation of subependymalglia
  • Tabesdoraslis
      • Result of damage by the spirochete to the sensory nerves in the dorsal roots
        • Impaired joint position sense and resultant ataxia, loss of pain sensation, skin and joint damage (Charcot joints), lightning pains – sensory disturbances
      • Micro – loss of both axons and myelin in the dorsal roots, pallor and atrophy in the dorsal columns of the spinal cord
neuroborreliosis symptoms
Neuroborreliosis– symptoms
  • Lyme disease
  • Caused by spirochete Boreeliaburgdorferi – transmitted by ticks (Ixodes)
  • Symptoms highly variable – aseptic meningitis, facial nerve palsies, mild encephalopathy, polyneuropathies
viral meningoencephalitis defn characteristic histo complications
Viral meningoencephalitis – defn, characteristic histo, complications
  • Viral encephalitis – parenchymal infection of the brain – associated with meningeal inflammation, sometimes involvement of the spinal cord
  • Characteristic histo: perivascularcuffs and parenchymal mononuclear cell infiltrates, glial cell reactions (microglial nodules), neuronophagia
  • Complications – congential malformations (intrauterine – rubella), postenecepahlitic parkinsonism, immune mediated disease – perivenousdemyelination
anthropod borne viral encephalitis epi clinical csf morphology
Anthropod-borne viral encephalitis – epi, clinical, CSF, morphology
  • Arboviruses – epidemic – tropical regions
  • In Australia – Murray Valley, in US – west nile virus
  • All animal hosts, mosquito vectors
  • Clinically – generalised neuro deficits – seizures, confusion, delirium, stupor, coma, focal signs, reflex asymmetry, ocular palsies
  • CSF – colourless, slightly elevated pressure, initially neutrophilpleocytosis converts to lymphocytes, protein level elevated, glucose normal
  • Morphology
    • Lymphocytic meiningoencephalitis – tendency for inflammatory cells perivascularly
    • Multiple foci of necrosis of gray and white matter
    • Neuronophagia – single cell neuronal necrosis with phagocytosis of the debris
    • Some cases prominent cortical involvement, others basal ganglia bear the brunt
hsv 1 epi symptoms morphology
HSV-1- epi, symptoms, morphology
  • Encephalitis – most common in children and young adults – 10% of patients had a history of prior herpes
  • Symptom – alterations in mood, memory, behaviour
  • Diagnosed with PCR
  • Morphology
    • Inferior and medial regions of the temporal lobes, orbital gyri of the frontal lobes
    • Necrotising, often hemorrhagic
    • Perivascular inflammatory infiltrate present
    • Cowdry type A intranuclear viral inclusion bodies – neurons and glia
  • Antiviral agents provide effective treatment
  • Some times – subacute course – weakness, lethargy, ataxia, seizures
other viral encephalitis hsv 2 herpes zoster cmv
Other viral encephalitis – HSV-2, herpes zoster, CMV
  • HSV-2 - Encephalitis – 50% of neonates delievered by vaginal birth to women with active primary HSV genital infection
    • AIDS – acute- hemorrhagic, necrotizing encephalitis
  • Herpes zoster (varicella) - Reactivation in adults – painful vesicular eruption – limited dermatomaldistribution, usually self-limited
    • Granulomatousarteritis
    • Immunosuppressed – acute necephalities – demyelination followed by necrosis
  • CMV
    • Foetuses and immunosuppressed
    • Utero – periventricular necrosis – serfver brain destruction – microcepahly – calcification
    • Most common pathogen in AIDS affecting CNS – 15-20%
    • Morphology
      • CMV inclusion bearing cells
      • Tendency for subependymal regions of the brain
      • Severe hemorrhagic necrotizing ventriculoencepahlitis and a choroid plexitis
poliomyelitis morphology clinical
Poliomyelitis – morphology, clinical
  • Still regions where it remains a problem
  • Causes subclinical or mild-gastritis – in a small fraction it invades the CNS
  • Morphology
    • Mononuclear cell perivascular cuffs and neuronophagia of the anterior horn motor neurons of the spinal cord
    • Cranial motor nuclei sometimes involved
  • Clinical
    • Initially meningeal irritation, may progress to involve the spinal cord
      • Flaccid paralysis – muscle wasting, hyporeflexia
    • Death can occur from paralysis
    • Myocarditis may also occur
    • Post-polio syndrome – may develop 25-35 years after resolution – progressive weakness associated with decreased muscle mass and pain, unclear pathogenesis.
rabies morphology clinical
Rabies – morphology, clinical
  • Severe encephalitis transmitted to humans by the bite of a rabid animal – dogs, bats etc
  • Morphology
    • Brain – oedema, vascular congestion
    • Micro – widespread neuronal degeneration, inflammatory reaction – most severe in the brainstem
    • Negri bodies – cytoplasmic, round to oval, eosinophilic inclusions that can be found in pyramidal neurons of the the hippocampus and Purkinje cells of the cerebellum – areas devoid of inflammation
  • Clinical
    • Virus enters CNS by ascending along peripheral nerves from wound site -> incubation period depends on distance between wound and brain -> typically 1-3 months
    • Early symptoms – malaise, headache, fever, local parathesias around the wound
    • As infection advances – extraordinary CNS excitability – slightest touch is painful, violent motor responses progressing to convulsions
    • Foaming – contracture of the pharyngel musculature on swallowing -> aversion to swallowing -> hydrophobia
    • Periods of alternating mania and stupor progress to coma and death
hiv morphology
HIV - morphology
  • Neuropathologic changes demonstrated at post-mortem in 80-90% of AIDs
  • HIV aspetic meningitis occurs within 1-2 weeks of seroconversion in 10% of patients
  • Morphology
    • Chronic inflammatory reaction
    • Microglial nodules – multinucleated giant cell
    • Especially in the subcortical white matter, diencephalon, brainstem
    • Disorder of white matter – multifocal or diffuse areas of myelin pallor, axonal swelling, gliosis
  • HIV related dementia – related to the extent of activated microglia in the brain
progressive multifocal leukoencephalopathy clinical morphology
Progressive multifocal leukoencephalopathy – clinical, morphology
  • Viral encephalitis – JC polyomarivurs – preferentially infects oligodendrocytes -> demyelination is the main effect
  • Exclusive to immunosuppressed individuals
  • Most people have serological exposure to JC virus by the age of 14 years
  • Clinically – focal, relentlessly progressive neurologic symptoms and signs
  • Imaging – extensive, often multifocal, lesions in the hemisphere or cerebellar white matter
  • Morphology
    • Patches of irregular, ill-defined destruction of the white matter – mm to entire lobes
    • Micro
      • Centre – lipid laiden macrophages, loss of axons
      • Edge – greatly enlarged oligodendrocytes nuclei – glassy amphophilic viral inclusions – viral antigen
      • May be bizarre giant astrocytes – one to several irregular, hyperchromatic nuclei
subacute scleroing panencephalitis
Subacute scleroingpanencephalitis
  • Rare progressive clinical syndrome – cognitive decline, spasticity of limbs, seizures
  • Occurs in children or young adults - after early-age acute infection of measles
  • Disease – altered measles virus in the CNS
  • Morph
    • Micro – widespread gliosis, myelin degeneration, viral inclusions -> nuclei of oligodendrocytes, neurons, also get neurofibrillary tangles
fungal meningoencaphlitis common agents patterns of infection
Fungal meningoencaphlitis – common agents, patterns of infection
  • Brain usually involved with widespread hematogenous dissemination
  • Most often – candidaalbicans, mucor species, aspergillus fumigates, Cryptococcus neoformans
  • Endemic areas – histoplasmacapsulatum, coccidiodiesimmitis, blastomycesdermatitidis
  • Three main patterns of fungal infection
    • Vasculitis – seen with mucromycosis and aspergillosis – direct fungal invasion of blood vessel walls, also seen in candidiasis
      • Vascular thrombosis produces infarction – usually hemorrhagic
    • Parenchymal invasion – granulomas or abscesses – often coexists with meningitis
      • Commonly – candida, Cryptococcus
      • Candida – multiple microabscesses
      • Mucormycosis – direct extension – common in DKA (?)
    • Chronic meningitis
cryptococcal meningitis csf morphology
Cryptococcal meningitis – CSF, morphology
  • Opportunistic infection – HIV/AIDs – may be fulminant and fatal
  • CSF – few cells, high protein – using India ink stain – yeasts can be visualised – in tissue use PAS or silver stains
  • Morphology
    • Chronic meningitis – basal leptomeninges – opaque, thickened by reactive tissue -> may obstruct outflow of CSF from the foramina of luschka and megendie -> hydrocephalus
    • Gelatinous material within subarachnoid space
    • Soap bubbles – small cysts in the parenchyma – prominent in basal ganglia
    • Parenchymal lesions – aggregates of organisms within perivascular (Virchow-Robin) spaces
cerebral toxicoplasmosis clinical morphology
Cerebral toxicoplasmosis – clinical, morphology
  • Opportunistic infection – HIV immunosuppression
  • Clinical symptoms – subacute –evolve over 1-2 wk period, focal or diffuse
  • Ring-enhancing lesion – not pathognomonic – also seen in lymphoma, TB, fungal
  • Non-immunosuppressed – pregnancy – cerebritis in the fetus -> multifocal cerebral necrotising lesions that may calcify -> severe damage to the developing brain
  • Morphology
    • Brain abscesses – gray-white junction, and deep gray nuclei
    • Acute lesions – central foci of necrosis, petechieal haemorrhages – chornic inflammation
    • Organisms seen on H&E, Giemsa stains
    • Blood vessels – fibrinoid necrosis, thrombosis
    • Treatment – coagulation necrosis surrounded by lipid-laiden macrophages
    • Chronic lesions – small cystic spaces, containing scattered lipid and hemosiderinlaiden macrophages
cerebral amebiasis
Cerebral amebiasis
  • Rapidly fatal necrotising encephalitis – naegleria species
  • Chronic granulomatousmeningoencepahlitis – acanthamoeba
  • Methenamine silver or PAS stains – visualise organisms
transmissible spongiform encephalopathies pathogenesis
Transmissible spongiform encephalopathies - pathogenesis
  • Prions – abnormal forms of cellular protein that cause transmissible neurodegenerative disorders
  • Path/molecular genetics
    • PrP 30-kD cellular protein in neurons
    • Disease – PrP undergoes conformational change from PrPc to PrPsc (alpha helix to beta pleated sheet)
    • With this change – resistant to digestion with proteases
    • Acumulation of PrPsc in neural tissue -> unsure how this causes a problem _. Cytoplasmic vacuoles -> neuronal death
    • PrPsc may be created normally at a very low rate
    • PrPsc facilitates the conversion of PrPc to PrPsc – infectious nature
    • PRNP – encodes PrP
      • Variety of mutations – familial forms
ckd and vckd
CKD and vCKD
  • Creutzfedlt-Jakob disease
    • Most common prion disease
    • Clinically – rapidly progressing dementia, startle myoclonus
      • Onset – subtle memory and behaviour changes
    • Incidence 1/million
    • Peak incidence in the 7th decade
    • Familial forms due to mutation in PRNP (codon 129 met or val)
    • Average survival 7 months from onset of symptoms
  • Variant creutzfedlt-Jakob disease
    • Affects young adults
    • Behavioural disorders appeared at early stages, neuro symptoms progress slower
    • Characterised – extensive cortical plaques with surrounding halo of spongiform change
    • Linked with bovine spongiform encephalopathy
morphology of ckd
Morphology of CKD
  • Progression to dementia so rapid – little cortical atrophy
  • Spongiform transformation of the cerebral cortex - uneven formation of small, apparently empty, microscopic vacuoles of varying size
  • Advanced stage – severe neuronal loss, reactive gliosis, expansion of vascuolated areas into cystlike spaces – status spongiosus
  • Kuru plaques – extracellular deposits of aggregates of abnormal protein – Congo-red or PAS positive
fatal familial insomnia
Fatal familial insomnia
  • Named after the sleep disturbances it causes
  • Specific mutation in PRNP gene
  • Lasts fewer than 3 years – neuro signs – ataxia, autonomic disturbances, stupor, coma
  • Morphology – no spongiform pathology, but there is neuronal loss andreactivegliosis in anterior ventral and dorsomedial nuclei of the thalamus, also inferior olivary nuclei
viral meningitis investigations management
Viral meningitis – investigations, management
  • Investigations
    • Dx by LP -> glucose normal, protein normal or slightly elevated, excess of lymphocytes -> VERIFY THAT ANITBIOTICS HAVE NOT BEEN GIVEN PRIOR TO LP
  • Management
    • Condition usually benign and self limiting
    • Recovery usually in days
    • Complete recovery without therapy is the rule
bacterial meningitis management
Bacterial meningitis - management
  • Management
    • Take specimens – blood culture, PCR, throat swab
    • Start empirical antibiotics
    • If no clinical signs indicating mass lesion, hydrocephalus, cerebral oedema – then – LP, otherwise CT first
bacterial meningitis treatment
Bacterial meningitis- treatment
  • Benzylpenicillinimmediately if bacterial meningitis suspected
  • Adults 18-50, meningococcal rash
        • Ceftriaxone
  • Suspected penicillin resistant pneumococcal infection
        • Ceftriaxone, vancomycin (or rifampicin)
  • Adults over 50, listeria is suspected
        • Ceftriaxone + ampicillin (or co-trimoxazole)
  • When the bacteria is known
        • N. meningitidis – benzylpenicillin
        • Strep pneumoniae – ceftriaxone
          • If resistant – vancomycin
        • H influenza – ceftriaxone
        • Listeriamonocytogenes – ampicillin plus gentamicin
        • Strep suis – cefriaxone
  • If allergic to penicillins – chloramphenicol, vancomycin
  • Coricosteroids – dexamethasone – limit to 2 days
viral encephalitis investigations management
Viral encephalitis – investigations, management
  • Investigations
    • CT/MRI – low density lesions in temporal lobe
    • LP – exclude mass lesion
      • Excess lymphocytes – polymorphonuclear cells may dominate in early stages, glucose normal, protein may be elevated
    • EEG usually abnormal in early stages – periodic slow wave activity in temporal lobes
    • PCR – viral DNA
  • Management
    • Anticonvulsant treatment is often necessary
    • Raised ICP -> dexamethasone
    • HSV – acyclovir -> should be given to all patients suspected of viral encephalitis
    • Mortality – 10-30%, surviviros – residual epilepsy, cognitive impairments
cerebral abscess investigations management
Cerebral abscess – investigations, management
  • Investigations
    • CT – single or multiple low density areas with ring enhancement (contrast), surrounding cerebral oedema
    • LP – if CT is ok
    • Elevated WCC and ESR
    • Consider cerebral toxicoplasmosis, or TB secondary to HIV
  • Management
    • Antimicrobial therapy once diagnosis is made
      • Site- source – organisms – treatment
      • Frontal lobe – paranasal sinuses, teeth – streptococci, anaerobes – cefuroxime, metronidazole
      • Temporal lobe – middle ear – streptococci, enterobaceteriaceae – ampicillin, metronidazole, ceftazidime (or gentamicin)
      • Cerebellum – sphenoid sinus, mastoid/middle ear – Pseudomonas, anaerobes - ampicillin, metronidazole, ceftazidime (or gentamicin)
      • Any site – penetrating trauama – staphylococci – flucloxacillin
      • Multiple – metastatic and cryptogenic – streptococci, anaerobes – benzylpencillin if endocarditis or cyanotic heart disease, otherwise cefuroxime plus metronidazole
    • Surgical treatment – burr-hole aspiriation, excision – esp if capsule
    • Anticonvulsants often necessary
    • Mortality 10-20% - may be related to delay in initiation of treatment
gullian barre syndrome clinical
Gullian-barre’ syndrome - clinical
  • Develops in 70% of patients 1-4weeks after RTI or diarrhoea – particaulrly campylobacter
  • Predominantely cell mediated inflammatory response directed at the myelin protein of spinal roots, peripheral and extra-axial cranial nerves -> complemented mediated destruction of myelin sheath and associated axon
  • Clinical – distal paraesthesia and limb pains – precede rapidly ascending muscle weakness
    • Facial and bulbar weaknes commonly develops
    • Ventilar support in 20%
    • Widespread loss of reflexes
    • 80% recover in 4-6 months, 4% die, rest have neuro deficits
gullian barre syndrome investigations management
Gullian-barre’ syndrome – investigations, management
  • Investigations
    • CSF – protein elevated at some stage of the illness, no rise in cell number
    • Electrophysiological studies – conduction blokd and multifocal motor slowing – delayed F waves
    • Identify underlying cause – campylobacter, CMV, mycoplasma
    • Acute porphyria – exclude by urinary porphyrin estimation
  • Management
    • Regularly monitor respiratory function
    • Corticosteroid shown to be ineffective
    • Plasma exchange and IV immunoglobulin shorten duration of ventilation assistance
myasthenia gravis clinical
Myasthenia gravis - clinical
  • 15-50, F > M in younger, reverse in older
  • Cardinal symptom – fatigable weakness of the muscles – movement initially strong, rapid weakening occurs – worsening symptoms towards end of day or after exercise is characteristic
  • No sensory signs or involvement of CNS – but weakness of oculomotor muscles may mimick a central eye movement disorder
  • First symptoms – ptosis, diplopia
    • Also – weakness of chewing, swallowing, speaking or limb movement
    • Limb muscle- commonly shoulder girdle
  • Respiratory failure is not an uncommon cause of death
  • Prognosis variable, remission spontaneously sometimes
    • If confined to eye muslces – prognosis excellent
    • Young F higher remission rates if thymectomy
    • Rapid progression more than 5 years after its onset is uncommon
myasthenia gravis investigations
Myasthenia gravis - investigations
  • Tensilon test
    • Inject – short acting anti-cholinesterase (edroponoium bromide) – test drug with small amount - then bigger amount 8 minutes later – improvement in muscle power occurs within 30 seconds persists for 1-2 minutes
  • Ice pack test
    • Ice on eye to help extra ocular muscles
  • Serological testing
    • AChRA is found in 50% of cases
    • Anti-MuSK (muscle specific kinase) especially in negative AChRA patients
    • 6-12% of patients are seronegative
  • Electrophysiological confirmation
    • Repeptitive nerve sitmulation
    • Single fibre
myasthenia gravis treatment
Myasthenia gravis - treatment
  • Principles of treatment
    • Maximise the activity of AchR in the neuromuscular junction
      • Anticholinesterase
        • Pyridostigmine – 30-120 mg, 6hourly
          • Muscarinic side effects
    • Limit or abolish the immunological attack on motor end plates
      • Thymectomy – antibody + under 25, symptoms not confined to extraocular eye muscles, unless disease established for more than 7 years
      • Plasma exchange – removing antibody blood – marked improvement – brief – crisis management, pre-operative
      • Plasmapheresis – remove offending autoantibodies
      • Intravenous immunoglobulin – alternative to plasma exchange in the short term treatment of severe myasthenia, MOA of action uncertain
      • Corticosteroid treatment – improvement commonly preceded by marked exacerbation of symptoms – should be initiated in hospital
        • Usually to continue for months to years
      • Others – azathioprine – reducing dosage of steroids
shigella clinical management
Shigella – clinical, management
  • Clinical
    • Burning discomfort in affected dermatome – discrete vesicles 3-4 days later
    • Severe disease suggests an underlying immunodeficiency
    • Thoracic dermatomes commonly involved
    • Ophthalmic division of trigeminal nerve is also involved
    • Ramsay Hunt syndrome – facial palsy, ipsilateral loss of taste and buccal ulceration, rush in the external auditory canal – geniculate ganglion involvement
    • Granulomatous cerebral angiitis – cerebrovascularcompliation – stroke-like syndrome
  • Management and prevention
    • Acyclovir – reduce early and late onset pain
    • Analgesia