Infection (neuro)

Question 1

What is the epidemiology of meningitis?

Answer 1

Most common in infants and children

Viral
i) More common than bacterial

Bacterial
i) Most cases are in the <16s

Question 2

What are the viral causes of meningitis?

Answer 2

Viral

i) Echovirus, mumps, herpes – EBV, Simplex, varicella zoster; influenza

Question 3

What are the bacterial causes of meningitis?

Answer 3

Bacterial
i) Neonate-3 months -
Ecoli, group B strep, Listeria monocytogenes
ii) 3 months-6yrs - Nisseria meningitides aka Meningococcus, Strep.pneumoniae, Haemophilis influenzae
iii) 6yrs+ - Meningococcus, S.pneumoniae
iv) TB can also cause (but this is rare in the UK)

Question 4

What are some non-infective causes of meningitis?

Answer 4

Leukemia, lymphoma, breast cancer, bronchial cancer, organ transplant, autoimmune disease, subarachnoid haemorrhage

Question 5

What is the pathophysiology of meningitis?

Answer 5

Viral < bacterial severity

Viral is often self limiting and can be overcome quickly

ii) Bacterial presents often when there is already an established infection and is common with septicaemia
iii) Meningococcal variant = particularly severe, but also has the lowest risk of long term complications in those that recover fully
iv) Pneumococcal variant = also high mortality as well as long term morbidity risks

Most of the damage comes from the host response and not the infective organism
i) WBCs release of excess inflammatory mediators → cerebral oedema → raised ICP → reduction of cerebral blood flow

Question 6

How does meningitis present?

Answer 6

Headache
Leg pains
Cold peripheries Meningism – neck stiffness, photophobia, Kernig’s sign
Decreasing GCS
Seizures ± focal signs
Petechial, non-blanching rash - glass test
Signs of shock

Question 7

What are some complications of meningitis?

Answer 7

i) Hearing loss – due to inflammatory damage to cochlear hair cells → children should have audiological follow up after meningitis
ii) Vascultits → cranial nerve lesions
iii) Cerebral infarct → focal seizures, long term epilepsy
iv) Hydrocephalus
v) Cerebral abscess
vi) Raised ICP

Question 8

How do you investigate meningitis?

Answer 8

Lumbar puncture

i) Usually diagnostic – unless Abx have been given before LP as false –ves
ii) Ensure patient does not have raised ICP before performing (usually done after CT)

Bloods

i) FBC – for raised WCC/thrombocytopenia, if low WCC = immunocompromised, seek help
ii) ABG – acidosis?
iii) Raised CRP
iv) Blood cultures

Throat swab cultures

Rapid antigen test
i) For blood, CSF or urine

If TB suspected
i) XR, mantoux etc

Question 9

What results do you expect on an LP for different types of meningitis?

Answer 9

Viral - lymphocytes, WCC 10-2000, colourless, >60% blood glucose (normal), protein = normal/low
Bacterial - granulocytes, WCC 1000-5000, turbid, low glucose, high protein

Question 10

How do you treat community presentation of meningitis?

Answer 10

Abx treatment as soon as meningococcal infection suspected i.e. <30mins of arrival - Cefotaxime, cephalexin = good broad spectrum choices – give IV, Benzylpenicillin as an alternative – give IM

Listeria infection -
ceftriaxone and ampicillin

Viral - Acyclovir, ibuprofen for fever, symptomatic management

Question 11

How do you treat hospital acquired presentation of meningitis?

Answer 11

Give the Abx as community above

Treat shock if present – fluids
Frozen plasma/platelet infusions
Consider dexamathasone → reduces long term complications (esp deafness)
Consider ventilation

Patients = most sick 8-12hrs after treatment due to release of bacterial toxins from lysed bacteria - assure patients this is normal

Question 12

How do you prevent meningitis?

Answer 12

Prevention

i) Meningococcal vaccine, protects against ACXYZ variants of N.meningitidis, no protection against the B strain
ii) HiB vaccine - against haemophilus has made this infection rare
iii) Conjugate pneumococcal vaccine

Prophylaxis

i) Rifampicin is given to all household contacts of a patient with meningococcal meningitis
ii) Men C vaccine if Men C meningitis etc

Question 13

What is the aetiology of encephalitis?

Answer 13

Mostly viral - HSV-1+2, arbovirusus, CMV, EBV, VZV, HIV (during seroconversion), measles, mumps, rabies, West Nile virus

Non viral - any bacterial meningitis, TB, malaria, listeria, Lyme disease legionella, leptospirosis

Question 14

What is the pathophysiology of encephalitis?

Answer 14

Intracranial infection → cerebral parenchymal inflammation
HSV-1 = particularly severe -
spreads from cranial nerve ganglia to frontal and temporal lobes

Question 15

What is the presentation of encephalitis?

Answer 15

Often mild, self limiting presentation i.e. headache, drowsniess, pyrexia, malaise; these can all become severe however Parenchymal signs – odd behaviour, low GCS, focal neurology i.e. cranial nerve palsies etc, seizure
Meningeal signs

Question 16

How do you investigate encephalitis?

Answer 16

Bloods - viral serology + PCR (though treatment should start before organism identified)

Contrast enhanced CT - focal bilateral temporal lobe involvement is suggestive of HSV encephalitis; meningeal enhancement suggests meningoencephalitis

Lumbar puncture: Post CT and ruling out raised ICP; moderate increase in protein and lymphocytes and decreased or normal glucose
i) A normal CSF doesn’t exclude encephalitis

EEG - may suggest diffuse abnormalities but may help confirm encephalitis

Throat swabs
MSU
Potential for brain biopsy

Question 17

How do you treat encephalitis?

Answer 17

Start acyclovir within 30 mins, continue for 2 weeks, 3 if immunosuppressed; adjust dose according to eGFR

Specific therapies for CMV + toxoplasmosis

Supportive therapy in HDU/ICU if necessary

Symptomatic treatment: phenytoin – seizures; dexamethasone – raised ICP