Subarachnoid Hemorrhage (SAH)

WHAT IS IT?

A subarachnoid hemorrhage (SAH) refers to bleeding that occurs in the subarachnoid space between the arachnoid membrane and the pia matter that surrounds the brain.

Anatomy of meningeal layers of the brain (source)
Anatomy of meningeal layers of the brain (source)

It can be caused by the rupture of an intracranial aneurysm (such as a saccular or berry aneurysm)

WHY IS IT A PROBLEM?

This type of hemorrhage progresses very rapidly, and can increase intracranial pressure in a very dangerous fashion.

WHAT MAKES US SUSPECT IT?

Risk factors: berry/saccular aneurysms, Marfan syndrome, Ehlers-Dalos syndrome, ADPKD, arteriovenous malformation, trauma

“Worst headache of my life” is the buzzword description for this condition. This headache is an acute one and also often co-presents with:

  • Nuchal rigidity (neck stiffness)
  • Vomiting
  • Confusion/altered level of conciousness
  • Oculomotor palsy
  • Neurological deficits
  • Seizures
HOW DO WE CONFIRM A DIAGNOSIS?

CT scan can help visualize the bleed and is faster and more sensitive for subarachnoid hemorrhage compared to MRI.

A non-contrast axial CT of the cranium demonstrates a left subarachnoid hemorrhage in the central sulcus (source)
A non-contrast axial CT of the cranium demonstrates a left subarachnoid hemorrhage in the central sulcus (source)

Lumbar puncture: bloody (will have increased RBCs) or yellow (xanthochromic) spinal tap can be suggestive of this process. The yellow color is due to the breakdown of bilirubin. A LUMPAR PUNCTURE IS CONDUCTED IF THE CT SCAN IS NEGATIVE

Source
Visual appearance of normal and xanthochromic CSF (source)

Cerebral angiography can reveal the causal aneurysm and aid in localizing treatment/intervention

Angiography showing a large aneurysm in the cerebral circulatory system (source)
Angiography showing a large aneurysm in the cerebral circulatory system (source)
HOW DO WE TREAT IT?

Treatment involves preventing the following processes from occurring: 

  • Re-bleeding: aneurysms can be clipped or coiled
  • Seizures
  • Vasospasm: nimodipine (CCB) is used to prevent this from occuring
  • Hydrocephalus 
HOW WELL DO THE PATIENTS DO?

This is a lethal condition. If the patient’s condition is not discovered in time death is very possible.

About half of all patients who survive this condition do so with some cognitive impairment (memory, mood neuropsychological function).

WAS THERE A WAY TO PREVENT IT?

If the cause is traumatic, the avoiding the initial trauma can prevent this condition.

WHAT ELSE ARE WE WORRIED ABOUT?

Cerebral vasospasm: 2-3 days after the initial bleed, there is a risk of vasospasm due to blood break down, which can cause a rebleed. This is why the medication nimodipine is used. A vasospasm is dangerous because it can lead to brain infarction! 

OTHER HY FACTS?

Rupture of Saccular (berry) aneurysms can lead to subarachnoid hemorrhage.

Most commonly found at the anterior circle of Willis at branch points of the anterior communicating artery (ACA).

ARCHIVE OF STANDARDIZED EXAM QUESTIONS 

This archive compiles standardized exam questions that relate to this topic.

FURTHER READING

DynaMed

UpToDate

 

Page Updated: 06.08.2016