Subarachnoid Vs Meningitis

Question 1

Subarachnoid haemorrhage causes bleeding the subarachnoid space, what effect does this have?

Answer 1

Early brain injury - Microthrombi / constriction, cerebral oedema, apoptosis

Cellular changes - Oxidative stress, release inflammatory mediators, platelet activation

Systemic complications -

3 days later - delayed cerebral ischaemia

Question 2

What are the risk factors for subarachnoid haemorrhage?

Answer 2

Trauma
Hypertension 
Smoking
Cocaine use
Excess alcohol
Aneurysms
Associated conditions: PKD, Neurofibromatosis, Marfans
Family history

Question 3

What is an aneurysm?

Answer 3

Abnormal weakness in vessel wall

Uncertain aetiology: `Abnormal weakening vs pressure effect, can be genetic.

90% are berry aneurysms. Absence of tunic media and lamina. Often congenital

Question 4

What could a painful 3rd nerve palsy indicate?

Answer 4

A posterior communicating artery aneurysm

Question 5

How does a patient with a subarachnoid haemorrhage present?

Answer 5

“worse headache I’ve ever had”

Presentation: Variable onset, explosive, severe, ‘thunderclap’ headache, diffuse, can last anything from an hour to a week.

Question 6

What other investigations do you do for subarachnoid haemorrhage?

Answer 6

CT head
If confirmed, CT angiogram
Lumbar puncture

Question 7

Describe the pathophysiology of meningits

Answer 7

Inflammation of the leptomeninges

Can be bacterial, viral or non-infective

1. Nasopharyngeal colonisation
2. Local invasion
3. Bacteremia (in blood)
4. Endothelial cell injury
5. Meningeal invasion
6. Subarachnoid space inflammation

5.Increased BBB permeability

Question 8

What are the classic symptoms of meningitis?

Answer 8

Fever, headache and nuchal rigidity

Question 9

What are the associated symptoms of meningitis?

Answer 9

Flu like symptoms, stiffness, photophobia, seizures, meningococcal rash (non-blanching), altered mental state, shock

Question 10

What pathogens can cause meningitis?

Answer 10

Neonates - E.coli, Group B strep, Lesteria

Children - H. influenza B, N. meningitides

Elderly - S. Pneumonia, L.monocutogenes

Question 11

Explain why you get a macular papular rash in Neisseria meningits?

Answer 11

Microvascular thrombosis:

Sluggish circulation

Low levels of protein C, S and antithrombin

Increased PA-1 - impaired fibrinolysis

Question 12

What are the risk factors of meningitis?

Answer 12

CSF defects 
Spinal procedures (epidural, lumbar puncture)
Endocarditis
Diabetes 
Alcoholism
Splenectomy
Crowded population e.g. student housing

Question 13

What investigations do you do for meningitis?

Answer 13

Blood including cultures and PCR
Lumbar puncture
CT if non-resolving
Possible general sepsis screen - CXR, MSU

Question 14

When do you NOT do a lumbar puncture?

Answer 14

Signs of raised ICP

Question 15

What is xanthochromia?

Answer 15

Yellow colouring of CSF

> 12 hours post bleed

More specific for SAH than blood stained CSF

Caused by red cell haemolysis into oxyhemoglobin then haem oxidase into Bilirubin.

Question 16

How do you treat somebody with a subarachnoid haemorrhage?

Answer 16

Neurosurgical referral - decompression surgery, coiling / clipping aneurysm

Neuro obs - look at trend

IV fluids - Aim 3L/day (high)

Nimodipine

Question 17

What are complications of subarachnoid haemorrhage?

Answer 17

Death - 50%
Re-bleed - 35%
Cerebral ischaemia 
Hydrocephalus 
Seizure - 5%
Disability

Question 18

How do you treat meningits?

Answer 18

Supportive: pain relief, anti-pyretics, IV fluids

Medical:
IV ceftriaxone
Dexamethasone to prevent hearing loss
If viral - depends on the virus -acyclovir for herpes, ganciclovir for CMV

Prognosis:
Leading cause of mortality due to infection in children under 5
Depends on age, pathogen condition ad severity of acute illness.
Viral meningits has excellent resolution

Question 19

What are the possible complications of meningits?

Answer 19

Septic shock 
DIC
Coma
Cerebral oedema
Raised ICP
Death
SIADH
Seizures 
Hearing loss
Intellectual defiicits
Hydrocephalus
Focal paralysis