Subarachnoid Haemorrhage (SAH)

Exam Cram

• Subarachnoid hemorrhage: bleeding the subarachnoid space (part of meninges)

• Presentation: thunderclap (acute onset) severe occipital headache 

• Diagnosis: CT-H, CT-Angio, lumbar puncture or MRI-H based upon timescale

• Management: coil > clip,  nimodipine

Outline

Background

• Associations: berry aneurysm (PCKD)

Assessment

History

• Thunderclap headache: 0-100 intensity < 5s

• Meningism: neck stiffness, photo/ phonophobia

• Raised ICP headache: vomiting, worse in morning/ evenings, worse on standing/ coughing

• Trigger: sympathetic drive- exercise, ejaculation

Examination

• Meningism: brunski & kernig's signs

• Papilloedema

Investigations

• CT-H: within 6 hours can rule out SAH

• Lumbar puncture: fresh blood or xanthochromia- after 12hrs

• CT-Angio: highly sensitive and specific

• MRI-H after 72hrs

• Troponin: mildly raised

• Coag required for LP

Scores

• Ottawa rules: if all negative can rule out SAH: 

Age > 40, neck pain/ stiffness , LOC, onset during exertion, thunderclap nature, limited neck flexion

Diagnosis

Diagnostic criteria: image findings on CT/ MRI

Differentials: Migraine / Cluster Headache ; Meningitis & Encephalitis ; Stroke- ischaemic or intracerebral haemorrhage

Classification: by aetiology

1. Spontaneous

   1. Idiopathic

   2. Secondary to 

      1. Berry Aneursym (Polycystic Kidney Disease )

      2. Arterial venous malformation

2. Traumatic

Management

• Medical: nimodipine

• Surgical

  • Coil > clip

  • CT-Angio required to show e.g. AVM or berry aneursym to coil

Med Reg Notes

Complications: hydrocephalus

CSF:  bilirubin - break down product of haemoglobin, causes the colour change called xanthochromia 

Concern is of microbleeds that are difficult to spot but have a risk of a further catastrophic bleed

Resources and References

1. https://www.mdcalc.com/calc/3875/ottawa-subarachnoid-hemorrhage-sah-rule-for-headache-evaluation

Written in 2025