=====Subarachnoid Haemorrhage=====
Common presentations:
  *Headache (48%)
  *Dizziness (10%)
  *Orbital pain (7%)
  *Diplopia (4%)
  *Visual loss (4%)

  *Sudden onset of severe headache - 'thunderclap'
  *nausea or vomiting
  *Symptoms of meningeal irritation
  *Photophobia and visual changes
  *Focal neurologic deficits
  *loss of consciousness
  *Seizures



  *Mild to moderate BP elevation
  *Temperature elevation
  *Tachycardia
  *Papilledema
  *Retinal haemorrhage
  *Global or focal neurologic abnormalities

<WRAP notice round 80%>Mortality of ~50% in 1st month\\ Rebleeds occur at the rate of 1-5% per day and 15-20% in 1st 2/52 </WRAP>
===CT scan===
  *may be -ve in 10-15% of patients
  *false -ve CT scan can result from severe anaemia or small-volume subarachnoid haemorrhage.
  *location of blood within the subarachnoid space correlates directly with the location of the aneurysm in 70% of cases.
    *In general, blood localized to the basal cisterns, the sylvian fissure, or the intra-hemispheric fissure indicates rupture of a saccular aneurysm.
    *Blood lying over the convexities or within the superficial parenchyma of the brain often is indicative of arteriovenous malformation (AVM) or mycotic aneurysm rupture.
    *Intra-parenchymal haemorrhage may occur with middle communicating artery and posterior communicating artery aneurysms.
    *Inter-hemispheric and intraventricular haemorrhages may occur with anterior communicating artery aneurysms

**The Fisher grading system is used to classify SAH:**
  *Grade 1 - No subarachnoid blood seen on CT scan
  *Grade 2 - Diffuse or vertical layers of SAH less than 1 mm thick
  *Grade 3 - Diffuse clot and/or vertical layer greater than 1 mm thick
  *Grade 4 - Intracerebral or intraventricular clot with diffuse or no subarachnoid blood

===Lumbar puncture===
  *may be -ve in 10-15%
  *may be -ve if performed <2/24, most sensitive 12/24 after onset of symptoms.
  *examines for RBC's and xanthochromia - traumatic tap will have greater RBC's in 1st tube vs SAH has greater no's in 3rd tube
  *no agreement on no. of RBCs required for Dx

==References include==
[[https://emedicine.medscape.com/article/1164341-overview|Emedicine SAH]]\\ 
[[https://onlinelibrary.wiley.com/doi/pdf/10.1111/acem.12811|LP post CTscan - ACEM review 2015]]\\