Infections of the Nervous System Flashcards
what is meningitis?
inflammation of the meninges, usually due to bacterial or viral infection
what is encephalitis?
inflammation of the brain substance
what is myelitis?
inflammation of the spinal cord
what are the most common causes of bacterial meningitis?
neisseria meningitis (meningococcus) and streptococcus pneumoniae (pneumococcus)
what is the most common cause of bacterial meningitis in neonates?
group B streptococcus which is usually contracted during birth from the mothers vagina
how does meningitis present?
fever, altered consciousness and seizures and meningism= neck stiffness, photophobia, nausea and vomiting
what is the hallmark of meningococcal meningitis?
non-blanching/petechial skin rash
what is the Kernig’s test?
patient lying on their back, flexing one hip and knee to 90 degrees and then slowly straightening the knee whilst keeping the hip flexed at 90 degrees= slight stretch in meninges and if meningitis will cause spinal pain or resistance in the movement
what is the Brudzinski’s test?
patient lying flat on their back and gently using your hands to lift their head and neck off the bed and flex their chin to their chest - positive if this causes the patient to involuntarily flex their hips and knees
how is bacteria meningitis managed?
take a blood culture and lumbar puncture for CSF and send blood tests for meningococcal PCR if meningococcal disease is suspected, then treat with ceftriaxone= antibiotic and dexamethasone
what is the most common cause of viral meningitis?
herpes simplex virus (HSV), enterovirus and varicella zoster virus (VZV)
how do we test for viral meningitis?
sample of CSF taken from the lumbar puncture and then send for a viral PCR testing
how is viral meningitis treated?
it tends to be milder than bacterial meningitis and so only requires supportive treatment
compare CSF from bacterial and viral infections.
B= cloudy, significantly raised protein level, low glucose, raised WCC, and bacterial culture V= clear, mildly raised or normal protein, normal glucose, raised WCC, negative culture
why do these differences in CSF make sense?
as bacteria will release proteins and use up the glucose but viruses dont use glucose but may release a small amount of protein
what are some possible complications of meningitis?
hearing loss, seizures, cognitive impairment, memory loss, focal neurological deficits
what are the contraindications to a lumbar puncture ?
swelling or mass within the brain as there its a risk that you can cone and reduce the pressure doing a LP so do a CT brain can before, new-onset seizures, papilledema, GCS <10, severe immunocompromised state
what is the most common cause of encephalitis in Europe?
herpes simplex (HSV) encephalitis- relatively rare though
how is viral encephalitis diagnosed and treated?
lab diagnosis by PCR of CSF for viral DNA and treated with acyclovir on clinical suspicion
what is typical of herpes infection?
once acquired you will always be infected as it remains latent in the body after primary infection - HSV types 1 and 2 cause cold sores and genital herpes - encephalitis rare complication of HSV but nearly always caused by type 1
what is a brain abscess?
localised area of pus within the brain
what is a subdural empyema?
thin layer of pus between the dura and arachnoid membranes over the surface of the brain
how does a subdural empyema and brain access present?
fever, headache, focal symptoms and signs, signs of raised ICP= papilledema, false localising signs, depressed conscious level, meningism, features of underlying source
what is tetanus?
infection with clostridium tentani, wound may not be apparent, the toxin acts on the NMJ and blocks inhibition of motor neurones causing rigidity and spasm, IV drug users= high risk group
how is tetanus prevented ?
immunisation and given combined with other antigens- penicillin and immunoglobulin for high-risk wounds/patients
what is botulism?
caused by clostridium botulinum which binds irreversibly to the presynaptic membranes of the peripheral neuromuscular and autonomic nerve junctions and this blocks acetylcholine release
what are post-infective inflammatory syndromes?
have a preceding infection or immunisation and will have latent interval between the precipitating infection and onset of neurological symptoms, it is autoimmune, in CNS= ADEM and in PNS= villain barre syndrome
what is Creutzfeldt-Jakob disease (CJD)?
a rare and fatal condition which affects the brain and caused by a prion
what are the 4 different aetiologies of CJD?
sporadic (usually over 60), new variant (younger onset), familial and acquired
how is CJD investigated?
MRI= pulvinar sign in variant CJD, EEG= generalised periodic complexes typical, CSF= normal or raised protein and immunoassay
how is CJD treated?
supportive as no cure
what is poliomyelitis?
caused by poliovirus types 1,2 or 3 and are all enteroviruses, more infections are asymptomatic but 1% have paralytic disease which infects the anterior horn cells of LMNs which cause an asymmetric, flaccid paralysis especially in the legs and will have no sensory features
what is rabies?
an acute infectious disease of the CNS affecting almost all mammals and is transmitted to human by bit or salivary contamination of open lesion and neurotropic virus enters peripheral nerves and then migrates to the CNS and causes paraesthesia at the site of original lesion and leads to ascending paralysis and encephalitis
what is neurosyphilis?
3 stage presentation= primary- normally a lesion on the genitals, secondary= more generalised disease, latent to tertiary disease- presents years/decades after the primary disease and is not common
how is neurosyphilis staged?
ration between treponema specific and non-treponema specific antibody tests
how is neurosyphilis treated?
high dose penicillin
