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
E. coli
Neisseria meningitidis
Listeria monocytogenes
intravenous cefotaxime + amoxicillin
0 - 3 months
* Group B Streptococcus (most common cause in neonates)
* E. coli
* Listeria monocytogenes
Meningitis: causes - 3 months - 6 years? [3]
Neisseria meningitidis
Streptococcus pneumoniae
Haemophilus influenzae
Meningitis: causes - 6 years - 60 years [2]
Neisseria meningitidis
Streptococcus pneumoniae
Describe the presentation of encephalitis in children [4]
- Altered consciousness
- Altered cognition
- Unusual behaviour
- Acute onset of focal neurological symptoms
- Acute onset of focal seizures
- Fever
Describe the clinical features of encephalitis [+]
Rapid onset of symptoms:
High fever: usually above 38°
- Often initial symptom
Severe headache
Altered Consciousness
- This is a critical sign suggestive of central nervous system involvement and mandates prompt evaluation.
Neurological Deficits
Focal Neurological Signs:
- Depending on the area of the brain affected, patients may exhibit focal neurological signs such as hemiparesis, aphasia or visual field defects.
Cranial Nerve Involvement:
- Cranial nerve palsies may occur, particularly affecting cranial nerves III, VI and VII leading to symptoms like diplopia or facial weakness.
Movement Disorders:
- Abnormal movements such as tremors, myoclonus or dystonia may be observed in some cases.
Meningeal Irritation:
- Signs of meningeal irritation including neck stiffness (nuchal rigidity), photophobia and positive Kernig’s or Brudzinski’s signs could be evident on physical examination
Seizures
- may be generalised or focal, and could represent the initial presenting symptom.
Rash: A rash may be present in some forms of encephalitis such as those caused by [2].
Rash: A rash may be present in some forms of encephalitis such as those caused by herpes simplex virus or enteroviruses.
Describe how the symptoms of meningitis differ from encephalitis [4 for each]
Meningitis:
- typically presents with headache
- fever
- neck stiffness (nuchal rigidity),
- photophobia
- and a positive Kernig’s or Brudzinski’s sign
Encephalitis:
- altered mental status
- seizures
- focal neurological signs such as hemiparesis or aphasia
- behavioural changes.
How would you dx encephalitis? [+]
Lumbar puncture, sending cerebrospinal fluid for viral PCR testing:
- Lymphocytosis
- Elevated proteins
- PCR for HSV, VZV and enteroviruses
CT scan if a lumbar puncture is contraindicated
MRI scan after the lumbar puncture to visualise the brain in detail:
- It can reveal areas of inflammation or oedema characteristic of encephalitis.
- medial temporal and inferior frontal changes
- normal in 1/3 patients
EEG recording can be helpful in mild or ambiguous symptoms but is not always routinely required:
- lateralised periodic discharges at 2 Hz
Swabs of other areas can help establish the causative organism, such as throat and vesicle swabs
HIV testing is recommended in all patients with encephalitis
How do you differentiate a brain abscess and encephalitis:
- with regards to clinical presentation and investigations [2]
Brain Abscess vs Encephalitis
Clinical Presentation:
- While both conditions can present with headache, fever, and focal neurologic deficits, patients with a brain abscess may also have symptoms related to increased intracranial pressure such as nausea, vomiting, and altered consciousness.
Investigations:
- Neuroimaging is essential for differentiation. MRI or CT scans can reveal a well-circumscribed lesion with surrounding oedema in the case of a brain abscess. In contrast, encephalitis typically presents with diffuse or multifocal areas of inflammation.
In cases where infectious causes are ruled out for encephalitis, what might you test for to ID the cause? [2]
Autoimmune antibody panel: In cases where infectious causes are ruled out, testing for autoimmune antibodies like NMDA receptor antibodies or LGI1/CASPR2 antibodies can help identify autoimmune encephalitis.
What are you specifically looking for on LP when assessing for encephalitis? [3]
Lumbar puncture, sending cerebrospinal fluid for viral PCR testing:
- Lymphocytosis
- Elevated proteins
- PCR for HSV, VZV and enteroviruses
How do you treat encephalitis? [3]
Aciclovir is usually started empirically in suspected encephalitis until results are available. Other viral causes have no effective treatment and management is supportive.
Intravenous antiviral medications are used to treat the suspected or confirmed underlying cause:
* Aciclovir treats herpes simplex virus (HSV) and varicella zoster virus (VZV)
* Ganciclovir treat cytomegalovirus (CMV)
Immunotherapy
* Corticosteroids may be considered in cases of immune-mediated encephalitis or post-infectious encephalomyelitis.
Manage seizures with appropriate antiepileptic drugs.
