Meningitis and subarachnoid haemorrhage Flashcards by Anannya Bhattacharya

What is a cistern?

An enlarged region located between arachnoid and pia

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What is the function go a cistern?

Collects CSF

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What are the functions of CSF?

Physical support of neural structures
Excretion of brain metabolites
Intracerebral transport
Control of chemical environment
COlume change reciprocally with volume of inter cranial contents

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What is the presentation of subarachnoid haemorrhage?

headache
Dizziness
Orbital pain
Diplopia
Visual loss
nausea vomiting

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What are the causes of subarachnoid haemorrhages?

Berry aneurysms (80%)

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Why do berry aneurysms develop?

Due to pressure on the arterial wall of vessels in the subarachnoid space at bifurcation points

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Which cerebral arteries are most affected?

Large anterior cerebral arteries in the anterior circle of willis
Anterior communicating artery

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Describe features of intracranial arteries?

Lack external elastic lamina and have thin adventitia

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What are risk factors of developing aneurysms?

Same as CVS- hypertension, smoking
Increased alcohol
Connective tissue disorders

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What are signs of subarachnoid haemorrhage?

Normal mental state
Signs of meningism
Third nerve palsy
No motor or sensory deficits

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What are signs of meningism?

Neck stiffness and photophobia

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Why is there a nerve palsy?

Posterior communicating artery aneurysm

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What are sentinel headaches in preceding months?

Minor leaks from aneurysms that seal up again

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What happens after a subarachnoid haemorrhage?

Microthrombi which can occlude smaller arteries
Vasoconstriction from CSF irritation
Cerebral oedema
Sympathetic activation- myocardial damage
Early rebleeding
Acute hydrocephalus
Global cerebral ischaemia

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What is the cerebral oedema a response to?

Hypoxia

Extravasated

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What are the investigations of subarachnoid haemorrhage, in order of what you’d do?

1st line- CT scan
Lumbar puncture
Angiography

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What would you see in a lumbar puncture after centrifugation?

Xanthochromia- blood breakdown/ bilirubin in CSF

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What is the treatment of subarachnoid haemorrhage?

Assessment on whether they need airway support
Monitoring CVS parameters
CCB (Nimodipine)
Operate on patients with good neurological status within 72 hrs
Clipping (open craniotomy)
Coiling (mauro-radiologists)

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What is involved in coiling treatment?

Insertion of wire into aneurysm sac which causes thrombosis of blood within aneurysm

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What is the prognosis for a subarachnoid haemorrhage?

Very poor prognosis
10-15% die before hospital
25% die within 24 hrs
40% within 1st month
Rebleeding occurs in up to 30% within 2 weeks in unoperated patients

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What are the two broad categories of CNS infections?

Parenchyma (encephalitis)

Meninges (Meningitis)

What is the more common area of meningitis?

Inflammation of the leptomeninges rather than dura

WHat is the most common cause of meningitis?

Infection

What are the signs and symptoms of meningitis?

Headache
Neck stiffness
Photophobia
Flu like
Joint pains
Rash
Reduced GCS

How long does it take to develop signs and symptoms?

Hours in bacterial and days in viral cause

WHat are some signs and symptoms of meningitis in babies?

Inconsolable crying/ high pitched Reduced feeds Floppy Bulging fontanelle

What is the most common cause of a rash in meningitis?

Meningococcal meningitis

What causes the rash?

Bleeding into skin or mucosa (microvascular thrombosis)

What sort of rash is produced?

Non blanching rash

What are large lesions in meningitis called and what are small called?

Large- purpuric | Smaller- petechial

Where are the most common areas of the body where the rash is found?

``` Trunk Legs Mucous membranes Conjuctivae Occasionally palms and soles More common in younger ```

What are the most common causative pathogens for meningitis?

``` Streptococcus pneumonia (Pneumococcal meningitis) Neisseria meningitides (Meningococcal meningitis) Haemophilus influenza (Hib meningitis) ```

What are the risk factors for community acquired bacterial meningitis?

Youngest and oldest are most affected Crowding Immune problems Cochlear implants

How does pneumococcus bacteria reach the CNS?

Colonisation of nasopharynx ascent from eustachian tube to the middle ear- prolonged infections like otitis media can cause spread of CSF or Seeding to lower respiratory tract (pneumonia) leading to lung inflammation allowing bacteria to enter blood

What happens to the meningitis bacteria when in the subarachnoid space?

No resistance to multiplication Inflammatory mediators induced Lots of leucocytes enter CSF Inflammatory cascade results in cerebral oedema and raised ICP

What are the complications of meningitis?

``` Septic shock DIC Coma Seizures Hearing loss Hydrocephalus Focal paralysis ```

How do you make a diagnosis of meningitis?

Symptoms and signs Physical exams Kernig sign Brudzinski

What is Kernig sign?

Supine patient with thigh flexed at 90 degrees Extension of knee is met with resistance More common in children

What is Brudzinski sign?

When knee is flexed there is an involuntary flexion of knee and hips when head is lifted up More common in children

What is the 1st line investigation of Meningitis?

Lumbar puncture | PCR

What would you find in the lumbar puncture in bacterial meningitis?

``` In untreated bacterial: Cloudy, high numbers of white cells Elevated protein Low glucose Positive gram stain ```

What would you find in the lumbar puncture in viral meningitis?

Clear or cloudy (immune cells and protein) Normal or raised protein Normal glucose

What is the treatment for viral meningitis?

Supportive fluids Anti-pyrexials NSAIDs Body recovers on its own

What is a risk of the raised ICP from meningitis?

Brain herniation

What are the clinical signs of brain herniation?

Decreasing consciousness Brainstem signs Recent seizure

What should be avoided in brain herniation?

Lumbar puncture

Why is a PCR done?

Helpful to diagnose patients who received empirical antibiotic treatment To distinguish bacterial from viral causes

What is the treatment for bacterial meningitis?

Empirical antibiotics Supportive therapy Dexamethasone

What are examples of empirical antibiotics?

Vancomycin and a cephalosporin (Ceftriaxone or Cefotaxime)

WHat is the treatment for viral meningitis?

Aciclovir for Herpes