Subarachnoid Hemorrhage (SAH)
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Introduction[edit | edit source]
15% of acute strokes are hemorrhagic strokes which are caused by bursting of a blood vessel i.e. acute hemorrhage. There are two main types of hemorrhagic strokes, intracerebral hemorrhage (ICH) and subarachnoid hemorrhage which accounts for about 5% of all strokes[1].
A subarachnoid hemorrhage (SAH) results from medical aneurysmal rupture or traumatic head injury. SAH occurs in the subarachnoid space between the arachnoid membrane and the pia mater that surrounds the brain. Patients typically present complaining of a severe headache; however, only 10% of patients presenting to the emergency department complaining of a thunderclap headache end up having a SAH. Associated symptoms may include neck pain, nausea/vomiting, and photophobia[2].
Because of the very high mortality, an interprofessional team that includes a radiologist, neurosurgeon, neurologist, intensivist and ICU nurses are ideal. Unfortunately, despite optimal case, the majority of patients die within 30 days. Even those who survive are left with severe complications that are disabling[2]. Worldwide SAH incidence and its decline show large regional differences and parallel the decrease in blood pressure and smoking prevalence.[3]
Clinically Relevant Anatomy[edit | edit source]
The brain and spinal cord are enveloped within three layers of membrane collectively known as the meninges, with the cranial meninges specifically referring to the section that covers the brain. From superficial to deep, the three layers are[4]
- dura mater - dense connective tissue and adheres to the inner surface of the skull and vertebrae
- arachnoid mater - thin wispy membrane that lies just deep to the dura and is superficial to the pia
- pia mater - the very thin, clear membrane that directly adheres to the surface of the brain and spinal cord.
Forming from these layers are three clinically significant spaces, or potential spaces (sometimes called cavities): the epidural, subdural and subarachnoid spaces, from superficial to deep. The chief function of the meninges is to protect the contents of the brain and spinal cord.
Subarachnoid hemorrhage is defined as blood between the arachnoid membrane and pia membrane, both layers of the dura mater.
Ninety percent of primary subarachnoid hemorrhages arise from congenitally derived arterial outpouchings (berry aneurysms) that lie at bifurcations of the major components of the circle of Willis. The most common sites are the carotid-posterior communicating and the anterior cerebral-anterior communicating artery junctions. Defects in the elastic membrane and media of the arteries are considered the basis for berry aneurysm formation[5].
Traumatic SAH: during the impact of an accident, the brain crashes back and forth inside the skull tearing blood vessels.
Mechanism of Injury / Pathological Process[edit | edit source]
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Clinical Presentation[edit | edit source]
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Diagnostic Procedures[edit | edit source]
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Outcome Measures[edit | edit source]
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Management / Interventions[edit | edit source]
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Differential Diagnosis[edit | edit source]
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References[edit | edit source]
- ↑ Tadi P, Lui F. Acute Stroke (Cerebrovascular Accident). Available from: https://www.ncbi.nlm.nih.gov/books/NBK535369/ (last accessed 2.1.2020)
- ↑ 2.0 2.1 Kairys N, Garg M. Acute Subarachnoid Hemorrhage (SAH). InStatPearls [Internet] 2019 May 4. StatPearls Publishing. Available from: https://www.ncbi.nlm.nih.gov/books/NBK518975/ (last accessed 2.1.2020)
- ↑ Etminan N, Chang HS, Hackenberg K, de Rooij NK, Vergouwen MD, Rinkel GJ, Algra A. Worldwide incidence of aneurysmal subarachnoid hemorrhage according to region, time period, blood pressure, and smoking prevalence in the population: A systematic review and meta-analysis. JAMA neurology. 2019 May 1;76(5):588-97. Available from:https://jamanetwork.com/journals/jamaneurology/fullarticle/2722652 (last accessed 2.1.2020)
- ↑ Ghannam JY, Al Kharazi KA. Neuroanatomy, Cranial Meninges. Available from:https://www.ncbi.nlm.nih.gov/books/NBK539882/ (last accessed 2.1.2020)
- ↑ DISORDERS OF THE NERVOUS SYSTEM - REEVES & SWENSON Chapter 27. Cerebrovascular disorders Available from:https://www.dartmouth.edu/~dons/part_3/chapter_27.html#chpt_27_ICH (last accessed 2.1.2020)
