Infections of the Nervous System

Question 1

what is meningitis?

Answer 1

inflammation of the meninges, usually due to bacterial or viral infection

Question 2

what is encephalitis?

Answer 2

inflammation of the brain substance

Question 3

what is myelitis?

Answer 3

inflammation of the spinal cord

Question 4

what are the most common causes of bacterial meningitis?

Answer 4

neisseria meningitis (meningococcus) and streptococcus pneumoniae (pneumococcus)

Question 5

what is the most common cause of bacterial meningitis in neonates?

Answer 5

group B streptococcus which is usually contracted during birth from the mothers vagina

Question 6

how does meningitis present?

Answer 6

fever, altered consciousness and seizures and meningism= neck stiffness, photophobia, nausea and vomiting

Question 7

what is the hallmark of meningococcal meningitis?

Answer 7

non-blanching/petechial skin rash

Question 8

what is the Kernig’s test?

Answer 8

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

Question 9

what is the Brudzinski’s test?

Answer 9

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

Question 10

how is bacteria meningitis managed?

Answer 10

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

Question 11

what is the most common cause of viral meningitis?

Answer 11

herpes simplex virus (HSV), enterovirus and varicella zoster virus (VZV)

Question 12

how do we test for viral meningitis?

Answer 12

sample of CSF taken from the lumbar puncture and then send for a viral PCR testing

Question 13

how is viral meningitis treated?

Answer 13

it tends to be milder than bacterial meningitis and so only requires supportive treatment

Question 14

compare CSF from bacterial and viral infections.

Answer 14

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

Question 15

why do these differences in CSF make sense?

Answer 15

as bacteria will release proteins and use up the glucose but viruses dont use glucose but may release a small amount of protein

Question 16

what are some possible complications of meningitis?

Answer 16

hearing loss, seizures, cognitive impairment, memory loss, focal neurological deficits

Question 17

what are the contraindications to a lumbar puncture ?

Answer 17

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

Question 18

what is the most common cause of encephalitis in Europe?

Answer 18

herpes simplex (HSV) encephalitis- relatively rare though

Question 19

how is viral encephalitis diagnosed and treated?

Answer 19

lab diagnosis by PCR of CSF for viral DNA and treated with acyclovir on clinical suspicion

Question 20

what is typical of herpes infection?

Answer 20

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

Question 21

what is a brain abscess?

Answer 21

localised area of pus within the brain

Question 22

what is a subdural empyema?

Answer 22

thin layer of pus between the dura and arachnoid membranes over the surface of the brain

Question 23

how does a subdural empyema and brain access present?

Answer 23

fever, headache, focal symptoms and signs, signs of raised ICP= papilledema, false localising signs, depressed conscious level, meningism, features of underlying source

Question 24

what is tetanus?

Answer 24

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

Question 25

how is tetanus prevented ?

Answer 25

immunisation and given combined with other antigens- penicillin and immunoglobulin for high-risk wounds/patients

Question 26

what is botulism?

Answer 26

caused by clostridium botulinum which binds irreversibly to the presynaptic membranes of the peripheral neuromuscular and autonomic nerve junctions and this blocks acetylcholine release

Question 27

what are post-infective inflammatory syndromes?

Answer 27

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

Question 28

what is Creutzfeldt-Jakob disease (CJD)?

Answer 28

a rare and fatal condition which affects the brain and caused by a prion

Question 29

what are the 4 different aetiologies of CJD?

Answer 29

sporadic (usually over 60), new variant (younger onset), familial and acquired

Question 30

how is CJD investigated?

Answer 30

MRI= pulvinar sign in variant CJD, EEG= generalised periodic complexes typical, CSF= normal or raised protein and immunoassay

Question 31

how is CJD treated?

Answer 31

supportive as no cure

Question 32

what is poliomyelitis?

Answer 32

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

Question 33

what is rabies?

Answer 33

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

Question 34

what is neurosyphilis?

Answer 34

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

Question 35

how is neurosyphilis staged?

Answer 35

ration between treponema specific and non-treponema specific antibody tests

Question 36

how is neurosyphilis treated?

Answer 36

high dose penicillin