Infections of the Nervous System Flashcards by Sophia Boyce

What is meningitis?

Inflammation/infection of the meninges

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What is encephalitis?

Inflammation/infection of brain substance

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What is myelitis?

Inflammation/infection of spinal cord

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In reality what is the distinction between meningitis, encephalitis and myelitis?

The distinction is artificial and patients often have a mixture

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What is the classical triad of meningitis?

Fever
Neck stiffness
Altered mental status

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How do patients with meningitis present?

With short history of progressive headache associated with fever (>38 degrees) and meningism (neck stiffness, photophobia, nausea + vomiting)

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How is neck stiffness examined?

By passively bending the neck forward

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What is commonly found in meningitis?

Cerebral dysfunction = confusion, delirium, declining conscious level, GCS <14 in 69%

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What 2 symptoms can occur in about 30% of meningitis patients?

Cranial nerve palsy
Seizures
(not necessarily both)

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What symptoms occurs in 10-20% of meningitis patients?

Focal neurological deficits

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What is the hallmark of meningococcal meningitis (but can also occur in viral meningitis)?

Petechial rash (tumbler test)

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What are the infective causes of meningitis?

Bacterial (neisseria meningitidis (meningococcus), strep pneumoniae (pneumococcus))
Viral (enteroviruses)
Fungal

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What is an inflammatory cause of meningitis?

Sarcoidosis

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What are the drug related causes of meningitis?

NSAIDs

IVIG (IV immunoglobin)

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What are the malignant causes of meningitis?

Metastatic
Haematological
e.g. Leukaemia, lymphoma, myeloma

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What are the main features of encephalitis?

Flu-like prodrome (4-10 days)

- Progressive headache associated with fever

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What are other features found in encephalitis?

+/- meningism
Progressive cerebral dysfunction (confusion, abnormal behaviour, memory disturbance, depressed conscious level)
Seizures
Focal symptoms/signs

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What is the different between viral and bacterial encephalitis?

Onset of viral encephalitis is slower than bacterial and cerebral dysfunction is a more prominent feature

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What is a viral cause of encephalitis?

Most commonly HSV

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What are inflammatory causes of encephalitis?

Limbic encephalitis (Anti VGKC, Anti NMDA receptors)
ADEM

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What are metabolic causes of encephalitis?

Hepatic
Uraemic
Hyperglycaemic

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What are malignant causes of encephalitis?

Metastatic

Paraneoplastic

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What other form of encephalitis is as common as viral encephalitis?

Auto-immune encephalitis

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What are the 2 important antibodies for auto-immune encephalitis?

Anti-VGKC (voltage gated potassium channel)

Anti-NMDA receptor

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Describe anti-VGKC auto-immune encephalitis

- frequent seizures - amnesia (not able to retain new memories) - altered mental state

Describe anti-NMDA receptor auto-immune encephalitis

- flu-like prodrome - prominent psychiatric features - altered mental state and seizures - progressing to a movement disorder and coma

What is the priority when investigating meningitis and encephalitis?

To exclude (and treat) infection

What are the 2 methods of investigation for meningitis?

- Blood cultures (bacteraemia) - Lumbar puncture (CSF culture/microscopy) No need for imaging if no contraindications to LP

What are the 4 methods of investigation for encephalitis?

- Blood cultures - Imaging (CT scan +/- MRI) - Lumbar puncture - EEG

What are the 5 indications for CT scan before lumbar puncture?

Focal neurological deficit, not inc cranial nerve palsies New-onset seizures Papilloedema Abnormal level of consciousness, interfering with proper neurological examination (GCS <10( Severe immunocompromised state

What do focal symptoms and signs suggest?

A focal brain mass

What does reduced conscious level suggest?

Raised ICP

Is lumbar puncture safe to carry out in meningitis?

Yes as brain is 'okay'; if problem is with brain - scan first

Describe the CSF finding of opening pressure in bacterial meningitis vs viral meningitis and encephalitis

BM = increased VM/E = normal/increased (gives idea of what kind of infection you are dealing with)

Describe the CSF finding of cell count in BM vs VM/E

BM = high, mainly neutrophils (polymorphs) VM/E = high, mainly lymphocytes (mononuclear cells) (main thing to look at in diagnosis)

Describe the CSF finding of glucose in BM vs VM/E

``` BM = reduced (bacteria use up glucose) VM/E = slightly increased ```

Describe the CSF finding of protein in BM vs VM/E

``` BM = high VM/E = slightly increased ```

First line treatment in suspected meningitis?

IV CEFTRIAXONE

What does a cloudy CSF indicate?

Large number of cells in sample

What should you do if the patient is presenting septic or pyrexial?

Do lumbar puncture but not blood culture

What is the commonest cause of encephalitis in Europe?

HSV (herpes simplex virus)

How is herpes simplex encephalitis diagnosed in the lab?

By PCR of CSF for viral DNA

What treatment should be given on clinical suspicion of herpes simplex encephalitis?

ACICLOVIR (then take sample and adapt with results)

What does a blood culture gram stain look like in bacterial meningitis?

Gram positive cocci in chains (look like streptococci) | Culture strep pneumoniae sensitive to penicillin

What is an appropriate investigation for herpes simplex encephalitis?

Lumbar puncture

What are the other 3 of the herpes group of viruses other than HSV?

VZV, EBV, CMV

What does HSV generally cause (types 1 + 2)?

- Cold sores (type 1 > 2) | - Genital herpes (type 1 + 2)

Where does the virus remain latent in HSV after primary infection?

In trigeminal or sacral ganglion (as with all herpes viruses - once infected, always infected - dormant until reduction of immunity etc)

What is a rare complication of HSV?

Encephalitis

Other than neonates, what type of HSV is encephalitis caused by?

Type 1

What are enteroviruses a large family of?

RNA viruses

What do enteroviruses have a tendency to cause?

CNS infections (neurotropic) (human infections, no animal reservoir)

How are enteroviruses spread?

Faecal-oral route

What type of meningitis can enteroviruses cause?

Non-paralytic

What 3 viruses are included in enteroviruses?

Polioviruses, coxsackieviruses, echoviruses

What other cause of encephalitis is common in other parts of the world?

Arbovirus encephalitides

How are arbovirus encephalitides transmitted?

To man via a vector (mosquito or tick) from non-human host

What types of encephalitis are caused by arbovirus encephalitides (variety of virus groups)?

- West Nile groups - St Louis encephalitis - Western Equine encephalitis - Tick Borne encephalitis - Japanese B encephalitis

Why is arbovirus called arbovirus?

ARthropod BOrne

What part of clinical history is crucial in diagnosing arbovirus encephalitide caused encephalitis?

Travel (travel history; some preventable by immunisation)

What is 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

What are some features found in a patient with brain abscess and empyema?

- Fever/pressure headache - Focal headache/signs - Signs of raised ICP - Meningism may be present (esp w empyema) - Features of underlying source

What are focal symptoms/signs of brain abscess/empyema?

Seizures, dysphasia, hemiparesis

What are signs of raised ICP?

Papilloedema, false localising signs, depressed conscious level

What are some features of underlying source found in brain abscess/empyema?

Dental, sinus or ear infection

What are some differential diagnoses for brain abscess and empyema?

- Any focal lesion, but most commonly tumour | - Subdural haematoma

List 4 causes of brain abscess and empyema

Penetrating head injury Spread from adjacent infection (dental, sinusitis, otitis media) Blood borne infection (bacterial endocarditis) Neurosurgical procedure

List 4 methods of diagnosing brain abscess/empyema

- Imaging (CT or MRI) - Investigate source - Blood cultures - Biopsy (drainage of pus)

What types of organisms are present in brain abscess?

Often mixtures of organisms present (polymicrobial) - dependant on predisposing condition Strep in 70% cases (esp penicillin-sensitive strep milleri) Anaerobes in 40-100% cases (bacteroides, prevotella)

What are 6 methods of management for brain abscess? (high mortality without appropriate treatment)

- Surgical drainage if possible - Penicillin or ceftriaxone to cover strep - Metronidazole for anaerobes - High doses required for penetration - Culture and sensitivity tests on aspirate provide useful guide

Infections of the Nervous System Flashcards

(71 cards)