Infections of the Nervous System Flashcards
(36 cards)
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
