Infections of the Nervous System Flashcards
What is meningitis?
Inflammation/ infection of the meninges
What is encephalitis?
Inflammation/ infection of brain substance
What is myelitis?
Inflammation/ infection of the spinal cord
What is the clinical features of meningitis?
Fever, neck stiffness and altered mental state
Short history of progressive headache and meningism
Can also have cerebral dysfunction (confusion or delirium), CN palsy, seizers, petechial skin rash
What symptoms are included in meningism?
Neck stiffness, photophobia, nausea and vomiting
What are some differential diagnosis for meningitis?
Bacterial, viral, fugal
Inflammatory - sarcoidosis
Drug induced - NSAIDs and IVIG
Malignant - metastatic and haematological
What are the bacterial and viral causes of meningitis?
Bacterial - Neisseria meningitidis (meningococcus) + Streptococcus pneumoniae (pneumococcus)
Viral - Enteroviruses
What are the clinical features of encephalitis?
Flu like prodrome (4-10days)
Progressive headache with fever, meningism, progressive cerebral dysfunction (confusion, memory disturbance, abnormal behaviour), seizers
What is the difference between viral encephalitis and bacterial meningitis?
Viral encephalitis has slower onset and more prominent cerebral dysfunction features
What are the differential diagnosis for encephalitis?
Viral (HSV)
Inflammatory - limbic encephalitis, ADEM
Metabolic - hepatic, uremic, hyperglycaemic
Malignant - metastatic, paraneoplastic
Migraine, post ictal (seizer)
What are the 2 important antibodies for auto-immune encephalitis?
Anti-VGKC (voltage gated potassium channel)
Anti-NMDA receptor
What are the symptoms of anti-VGKC auto-immune encephalitis?
Frequent seizers, amnesia and altered mental state
What are the symptoms of anti-NMDA receptor auto-immune encephalitis?
Flu like prodrome, prominent psychiatric features, altered mental state and seizers, progressing to movement disorder and coma
What investigations are used for meningitis?
Blood cultures, lumbar puncture and no need for imaging if no contraindications to LP
What investigations are used for encephalitis?
Blood cultures, imaging (CT and maybe MRI), lumbar puncture and EEG
What are some contraindications for a lumbar puncture?
Focal symptoms and signs suggest focal brain mass
Reduced consciousness suggests raised ICP
New onset seizers
Papilledema
What are the CSF findings for bacterial meningitis?
Increased opening pressure
High WCC - mainly neutrophils
Reduced glucose compared to blood
High protein
What are the CSF findings for viral meningitis and encephalitis?
Normal or increased opening pressure
High WCC - mainly lymphocytes
Normal glucose
Slightly increased protein
What is culture streptococcus pneumoniae sensitive to?
Penicillin
Describe HSV encephalitis
Commonest cause in Europe
Lab diagnosis by PCR of CSF for viral DNA
Treat with aciclovir on clinical suspicion
Describe herpes simplex
Types 1 and 2 cause cold sores and genital herpes
Virus remain latent in trigeminal or sacral ganglion after primary infection
Encephalitis is rare complication of HSV
Describe enteroviruses
Spread by faecal oral route
Tendency to cause CNS infections, human infection and not animal
Do not cause gastroenteritis
Included poliovirus, coxsackieviruses and echoviruses
Describe Arbovirus encephalitis
Common in other parts of the world
Transmitted by vector from non-human host - arthropod borne
Relevant to travel
What are brain abscesses and empyema?
Brain abscess - localised area of pus within brain
Empyema - thin layer of pus between dura and arachnoid membrane over surface of brain
What are the clinical features of brain abscess and empyema?
Fever, headache, focal symptoms (seizers, dysphagia, hemiparesis)
Signs of raised ICP - depressed conscious state and papilledema
Meningism with empyema
Features of underlying source
What are the cause for brain abscess and empyema?
Penetrating head injury, spread from adjacent infection, blood borne infection, or neurosurgical procedure
How is brain abscess or empyema diagnosed?
CT or MRI, investigate source, blood cultures and biopsy (drainage of pus)
What organisms can cause brain abscess?
Polymicrobial
Streptococci in most - esp. in penicillin sensitive strep milleri group
Anaerobes in most
Describe the management for brain abscesses
Surgical drainage if possible
Penicillin or ceftriaxone to cover strep
Metronidazole for anaerobes
Culture and sensitivity tests
High mortality without treatment
What are some HIV indicator illnesses of the brain?
Cerebral toxoplasmosis, aseptic meningitis/ encephalitis, primary cerebral lymphoma, cerebral abscess, cryptococcal meningitis, dementia and leukoencephalopathy
What infections can be seen in HIV patients with low CD4 counts?
Cryptococcus neoformans, toxoplasma gondii, HIV-encephalopathy
What diagnostics are used for HIV indicator illnesses?
Cryptococcal antigen, toxoplasmosis serology, CMV PCR and HIV PCR
What spirochaetes could be in the CNS?
Lyme disease
Syphilis
Leptospirosis
Describe Lyme disease
Vector borne - tick
Borrelia burgdorferi
Has 3 stages and is multisystem
What is stage 1 of Lyme disease?
Early localised infection - characteristic expanding rash at site of bite (erythema migrans)
Mainly flu like symptoms
What is stage 2 of Lyme disease?
Early disseminated infection weeks or months after
Musculoskeletal and neurological involvement most common
More PNS than CNS
What is stage 3 of Lyme disease?
Chronic infection months to years after
Musculoskeletal and neurological involvement common
Subacute encephalopathy and encephalomyelitis
What is the investigation and treatment of Lyme disease?
Range of serological tests, CSF lymphocytosis, MRI brain, nerve conduction studies
Prolonged antibiotic treatment - IV ceftriaxone or oral doxycycline
Describe neurosyphilis
3 stage presentation - primary, secondary and latent
Tertiary disease is years or decades after primary
Treponema specific and non treponemal specific antibody tests
CSF lymphocytes increased
High dose penicillin
Describe poliomyelitis
Caused by poliovirus type 1,2 or 3 - all enteroviruses
Paralytic disease in 1% - anterior horn cells of LMN affected
Asymptomatic, flaccid paralysis esp. legs
Describe rabies
Acute infectious disease of CNS affecting almost all mammals
Transmitted to human by bite or salivary communication
Neurotropic
Paraesthesia at site
Ascending paralysis and encephalitis
Describe rabies encephalitis
No clinical diagnostic test before disease apparent
Diagnosis by PCR and serology
Sedation, intensive care needed and possible death
What is used for pre-exposure prevention?
Active immunisation with killed vaccine
In UK - bat handlers, imported animal handlers and selected travellers
What is rabies post-exposure treatment?
Wash wound, give active rabies immunisation, and give rabies immunoglobin
Describe tetanus
Infection with clostridium tetani
Anaerobic gram positive bacillus and spore forming
Toxin acts at NMJ
Blocks inhibition of motor neurons
Rigidity and spasm
Describe the prevention of tetanus
Immunisation
Give combined with other antigens
Penicillin and immunoglobulin for high risk wounds/ patients
Describe botulism
Clostridium botulinum - anaerobic spore producing gram positive bacillus
Neurotoxin
Naturally presents in soil, dust and aquatic environments
Modes of infection - infantile, food, wound
What is the presentation of botulism?
Incubation period 4-14 days, descending symmetrical flaccid paralysis, pure motor, respiratory failure and autonomic dysfunction
What is the diagnosis and treatment of botulism?
Nerve conduction studies, mouse neutralisation bioassay for toxin in blood and culture
Treatment is antitoxin, penicillin/ metronidazole and radical wound debridement
What are some post infective inflammatory syndromes?
CNS - acute disseminated encephalomyelitis
PNS - Guillain Barre syndrome
Preceding infection or immunisation - molecular mimicry, latency and autoimmune
Describe Creutzfeldt-Jacob disease
Transmissible proteinaceous particle - prion
Aetiology - sporadic CJD, new variant, familial and acquired
What are the clinical features of sporadic CJD?
Rapidly progressive dementia
Insidious onset, early behavioural abnormalities, myoclonus, progressive neurological decline, motor abnormalities and seizers
What are the differential diagnosis for sporadic CJD?
Alzheimer’s disease
Subacute sclerosing pan encephalitis
CNS vasculitis
Inflammatory encephalitis
What is the prognosis of sporadic CJD?
Rapid progression and death often within 6 months
Describe new onset variant CJD
Younger onset <40
linked to bovine spongiform encephalopathy in cattle
Early behavioural changes are common
Longer course
What are the investigations for CJD?
MRI - pulvinar sign in variant but usually no specific changes in sporadic
EEG - generalised periodic complexes typical
CSF - normal or raised protein, immunoassay 14-3-3 brain protein
