Meningitis and Encephalitis (do Encephalitis) Flashcards
The meninges are composed of three individual layers.
What are they? [3]
Dura mater: tough outer membrane. Lies directly beneath the skull. Composed of two layers: outer periosteal layer and inner meningeal layer.
Arachnoid mater: avascular layer of connective tissue that sits beneath the dura mater. Beneath the arachnoid mater is the subarachnoid space that contains cerebrospinal fluid.
Pia mater: thin inner membrane. Tightly adherent to the brain and spinal cord.
What are the clinical features of viral meningitis [6]
- headache
- evidence of neck stiffness
- photophobia (often milder than the photophobia experienced by a patient with bacterial meningitis)
- confusion
- fevers
- may have focal neurological deficits on examination, although again this is less frequently observed in viral as in bacterial meningitis
What are the first line Ix for ?viral meningitis? [3]
What are further Ix might conduct? [3]
First-line Investigations
Lumbar Puncture:
- This is the most important investigation in suspected cases of viral meningitis
- It allows for collection of cerebrospinal fluid (CSF) which can be analysed for signs suggestive of viral infection such as lymphocytic pleocytosis, normal or slightly elevated protein levels, and normal glucose levels.
CSF Polymerase Chain Reaction (PCR):
- This test is used to identify specific viral genetic material in the CSF. It has high sensitivity and specificity for detecting common causes of viral meningitis such as Enteroviruses, Herpes simplex virus, Varicella zoster virus, and others.
Blood Tests:
- Full blood count, C-reactive protein (CRP), and blood cultures may be performed to exclude bacterial infection. Additionally, liver function tests may be useful in evaluating patients with suspected mumps meningitis.
Secondary Ix:
Magnetic Resonance Imaging (MRI) or Computed Tomography (CT):
- These imaging studies might be necessary if there are focal neurological signs or symptoms suggestive of complications like cerebral oedema or abscess formation. However, they are not routinely required in uncomplicated cases.
Serological Testing
- In some cases where PCR is negative but suspicion remains high, serological testing may be useful. This involves measuring antibody levels against specific viruses in the blood to determine if a recent infection has occurred.
Viral Culture:
- While CSF PCR is generally more sensitive and faster, viral culture from CSF, throat swabs or faecal samples can still play a role in diagnosis especially for less common viruses not covered by standard PCR tests.
What is the Mx of viral menigitis?
Viral meningitis is self-limiting, with** symptoms improving over the course of 7 - 14 days** and complications are rare in immunocompetent patients.
What are possible complications of viral men:
- Acute complications [3]
Acute complications:
Cerebral oedema:
- This is the most immediate and potentially life-threatening complication. Patients may present with altered consciousness, seizures, focal neurological signs or even coma. Prompt identification and management are essential.
Seizures:
- Seizures can occur secondary to cerebral irritation. Anticonvulsant therapy may be required.
Syndrome of inappropriate antidiuretic hormone (SIADH):
- SIADH can result in hyponatraemia leading to seizures, headache and nausea. Management involves fluid restriction and careful monitoring of electrolyte levels.
What are possible complications of viral men:
- Long term complications [2]
Cognitive impairment:
- Cognitive deficits including memory loss, difficulty concentrating and behavioural changes can persist post-recovery.
Hearing loss:
- Sensorineural hearing loss is a recognised complication of viral meningitis due to damage to the auditory nerve. Regular audiological assessments should be conducted in the recovery phase.
What is the most common cause of meningitis in children and adults are [2]
What is the most common cause in neonates? [1]
Bacterial meningitis is inflammation of the meninges caused by a bacterial infection. The most common causes of bacterial meningitis in children and adults are Neisseria meningitidis (meningococcus) and Streptococcus pneumoniae (pneumococcus).
In neonates the most common cause is group B strep (GBS). GBS is usually contracted during birth from GBS bacteria that live harmlessly in the mother’s vagina.
Describe the CSF changes in meningitis for bacterial, viral and TB infections
- appearance
- cell type present
- protein content
- glucose content
What else do you need to do when getting an LP? [1]
Bacterial
- Cloudy
- Neutrophils
- High protein
- Glucose < 60% of blood
Viral:
* Clear
* Lymphocytes
* Normal/raised protein
* Normal glucose
TB:
- Slight cloudy, fibrin web, opalescent
- Lymphocytes
- High protein
- Glucose < 60% of blood
Also need paired blood test to compare to LP
NB: beware a partially completed bacterial infection as it presents as a lymphocytic / viral picture
A child has been treated for meningitis and discharged.
You arrange a follow up - when and what for? [2]
Follow up in 4 weeks for audiology and neurodevelopment
- Esp if HiB infection
You give IX dexamethasone for ?meningitis.
Once microscopy has come back you continue this tx. Which organisms would mean you do this? [2]
Continue IV dex if pneumococcus or HiB
Contacts of a patient with a patient with meningococcal infections such as meningitis or septicaemia should be given what as PEP? [1] When? [1]
The usual antibiotic choice for this is a single dose of ciprofloxacin. It should be given as soon as possible and ideally within 24 hours of the initial diagnosis.
Children seen in the primary care setting with suspected meningitis AND a non blanching rash should receive an urgent stat injection of [] prior to transfer to hospital, as time is so important. The dose will depending on their age.
Children seen in the primary care setting with suspected meningitis AND a non blanching rash should receive an urgent stat injection (IM or IV) of benzylpenicillin prior to transfer to hospital, as time is so important. The dose will depending on their age.
How do the symptoms of viral meninigitis differ from bacterial meningitis? [2]
viral meningitis
- Both can present with symptoms such as headache, fever, neck stiffness, and photophobia.
- often have a less severe course of illness compared to those with bacterial meningitis.
- They are generally less systemically unwell and may lack the marked neurological signs seen in bacterial meningitis.
How do the symptoms of encephalitis meninigitis differ from bacterial meningitis? [2]
Can present similarly to meningitis.
However, encephalitis typically presents with altered mental status or focal neurological deficits not usually seen in bacterial meningitis
- The presence of seizures at onset is more common in encephalitis than in bacterial meningitis.
Lumbar puncture should be delayed in which circumstances? [5]
- signs of severe sepsis or a rapidly evolving rash
- severe respiratory/cardiac compromise
- significant bleeding risk
- signs of raised intracranial pressure
- focal neurological signs
- papilloedema
- continuous or uncontrolled seizures
- GCS ≤ 12
If an LP has been performed, the CSF should be tested for: [+]
- glucose, protein, microscopy and culture
- lactate
- meningococcal and pneumococcal PCR
- enteroviral, herpes simplex and varicella-zoster PCR
- consider investigations for TB meningitis
Label A-G [6]
You suspect meningitis
They have had a previous bad reaction to penicillin.
What do you give instead? [1]
If the patient has a history of immediate hypersensitivity reaction to penicillin or to cephalosporins the BNF recommends using chloramphenicol.
What is this specific rash called? [1]
Meningococcal skin rash (purpura fulminans)
Particularly in meninigitis cases caused by H. influenzae, [] is a significant side effect [1]
Hearing loss: Sensorineural hearing loss is a frequent sequela, may be permanent.
Seizures are a complication of bacterial meningitis.
What is the most likely pathogen causing this? [1]
Seizures: These may be either focal or generalised, and are more common in patients with pneumococcal meningitis caused by Streptococcus pneumoniae.
Streptococcus pneumoniae
Cloudy appearance, glucose 70% of plasma, protein 0.5 g/l, WCC 500 per mm^3 (lymphs) - viral meningitis
The following CSF report is received for a patient with fever and headache: cloudy appearance, glucose 25% of plasma, protein 1.5 g/l, WCC 2,000 per mm^3 (neuts)
What is the most likely cause? [1]
Bacterial
