Subarachnoid Haemorrhage

Subarachnoid haemorrhage involves bleeding in to the subarachnoid space, where the cerebrospinal fluid is located, between the pia mater and the arachnoid membrane. This is usually the result of a ruptured cerebral aneurysm.

Subarachnoid haemorrhage has a very high mortality and morbidity. It is very important not to miss the diagnosis and you need to have a low suspicion to trigger full investigations. It needs to be discussed with the neurosurgical unit with a view to surgical intervention.


Thunderclap Headache

The typical history is a sudden onset occipital headache that occurs during strenuous activity such as weight lifting or sex. This occurs so suddenly and severely that it is known as a “thunderclap headache”. It is described like being hit really hard on the back of the head. Other features are:

  • Neck stiffness
  • Photophobia
  • Vision changes
  • Neurological symptoms such as speech changes, weakness, seizures and loss of consciousness


Risk Factors

  • Hypertension
  • Smoking
  • Excessive alcohol consumption
  • Cocaine use
  • Family history


Subarachnoid haemorrhage is more common in:

  • Black patients
  • Female patients
  • Age 45-70


It is particularly associated with:

  • Cocaine use
  • Sickle cell anaemia
  • Connective tissue disorders (such as Marfan syndrome or Ehlers-Danlos)
  • Neurofibromatosis
  • Autosomal dominant polycystic kidney disease



CT head is the first line investigation. Immediate CT head is required. Blood will cause hyperattenuation in the subarachnoid space.


Lumbar puncture is used to collect a sample of the cerebrospinal fluid if the CT head is negative. CSF can be tested for signs of subarachnoid haemorrhage:

  • Red cell count will be raised. If the cell count is decreasing in number over the samples, this could be due to a traumatic lumbar puncture.
  • Xanthochromia (the yellow colour of CSF caused by bilirubin)


Angiography (CT or MRI) can be used once a subarachnoid haemorrhage is confirmed to locate the source of the bleeding.



Patients should be managed by a specialist neurosurgical unit. Patients with reduced consciousness may require intubation and ventilation. Supportive care as part of a multi-disciplinary team is important with good nursing, nutrition, physiotherapy and occupational therapy involved during the initial stages and recovery.

Surgical intervention may be used to treat aneurysms. The aim is to repair the vessel and prevent re-bleeding. This can done by coiling, which involves inserting a catheter into the arterial system (taking an “endovascular approach”), placing platinum coils into the aneurysm and sealing it off from the artery. An alternative is clipping, which involves cranial surgery and putting a clip on the aneurysm to seal it.

Nimodipine is a calcium channel blocker that is used to prevent vasospasm. Vasospasm is a common complication that can result in brain ischaemia following a subarachnoid haemorrhage.

Lumbar puncture or insertion of a shunt may be required to treat hydrocephalus.

Antiepileptic medications can be used to treat seizures.


Last updated April 2019
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