Subarachnoid Hemorrhage Overview

Overview of Subarachnoid Hemorrhage

• Definition: Subarachnoid hemorrhage (SAH) refers to bleeding within the subarachnoid space, located between the arachnoid and pia mater, typically filled with cerebrospinal fluid (CSF).

Stroke Types

• Classification of Stroke:

  • Stroke is defined as a syndrome of acute, focal neurological deficit attributed to vascular injury.

  • Types of Stroke:

  • Ischemic Stroke:

    • Caused by blockage of blood vessels; results in a lack of blood flow to the affected area.

  • Hemorrhagic Stroke:

    • Results from rupture of blood vessels; causes leakage of blood.

    • Intracerebral hemorrhage

    • Subarachnoid hemorrhage

Incidence of Subarachnoid Hemorrhage

• Epidemiology:

  • SAH accounts for approximately 5% of all strokes.

  • Incidence rates of aneurysmal SAH (aSAH) range from 2 to 16 per 100,000 person-years.

Etiology of Subarachnoid Hemorrhage

• Causes:

  • Most commonly caused by saccular aneurysms, particularly at the Circle of Willis or its major branches, especially at bifurcations.

  • Proportion of cases:

  • Ruptured saccular aneurysms: 80-85%

  • Nonaneurysmal SAH: 15-20%

Risk Factors for Aneurysm Rupture

• Annual Risk:

  • The annual risk of rupture of an asymptomatic aneurysm is approximately 0.7%.

• Increased Risk:

  • Aneurysm size

  • Prior SAH from a separate aneurysm

  • Location at posterior communicating artery

  • Lifestyle factors (cigarette smoking, hypertension)

  • Symptoms indicate potential risk: aneurysm-related headache.

Clinical Findings

• Symptoms of SAH:

  • Sudden-onset severe headache, often described as "the worst headache of my life".

  • Headache may be the only symptom initially, with prodromal symptoms often leading to a sentinel headache.

  • Other clinical manifestations may include:

  • Loss of consciousness

  • Neck pain or stiffness

  • Vomiting

  • Seizures

  • Sudden death

Physical Examination

• Meningismus: Sign of irritation of the meninges.

• Hypertension: May be present.

• Assessment for Kernig's and Brudzinski's Signs: Indicators of meningeal irritation.

• Terson syndrome: Presence of preretinal hemorrhages.

• Pupil-involving third nerve palsy: Includes signs like ptosis, mydriasis; abnormal eye positions ("down and out").

Classification of Subarachnoid Hemorrhage

• Hunt and Hess Scale:

  • Grade I: Asymptomatic or mild headache with slight nuchal rigidity - Survival 70%

  • Grade II: Moderate to severe headache, nuchal rigidity, no neurological deficit other than cranial nerve palsy - Survival 60%

  • Grade III: Drowsiness, confusion, or mild focal deficit - Survival 50%

  • Grade IV: Stupor, moderate to severe hemiparesis, possibly early decerebrate rigidity - Survival 20%

  • Grade V: Deep coma, decerebrate rigidity, moribund appearance - Survival 10%

• Modified Fisher Scale: Assesses CT findings related to SAH for predicting symptomatic vasospasm.

Diagnosis of Subarachnoid Hemorrhage

• Initial Assessments:

  • Noncontrast head CT is the first test; may show hemorrhage.

  • Lumbar puncture to analyze CSF; often grossly bloody in SAH cases.

  • CTA/MRA/DSA are methods for detecting intracranial aneurysms and defining their anatomy.

• Digital Subtraction Angiography (DSA): Considered the gold standard for testing.

  • Highest resolution for detection of intracranial aneurysms.

  • Can facilitate endovascular treatment concurrently.

Complications of Subarachnoid Hemorrhage

• Common Complications:

  • Vasospasm (delayed cerebral ischemia)

  • Hydrocephalus

  • Rebleeding

Prognosis of Subarachnoid Hemorrhage

• Risk of Rebleeding:

  • Highest risk occurs within the first 24 hours post-hemorrhage; prognosis is poor for patients who rebleed.

• Delayed Cerebral Ischemia (Vasospasm):

  • Begins 3 to 5 days after hemorrhage, peaking at 5 to 14 days.

  • Gradually resolves over 2 to 4 weeks.

• Hydrocephalus:

  • Acute hydrocephalus occurs in 15-20% of SAH cases.

  • Delayed hydrocephalus can develop 3 to 21 days after SAH.

Special Cases in Subarachnoid Hemorrhage

• Nonaneurysmal subarachnoid hemorrhage:

  • Typically identified in various contexts, including:

  • Perimesencephalic hemorrhage, characterized by blood confined to perimesencephalic cisterns near the midbrain and pons, associated with benign clinical course.

  • Cerebral amyloid angiopathy (CAA) seen as a common form in the elderly leading to convexity SAH.

  • Intracranial arterial dissection leading to hemorrhage.

  • Other risks include bleeding disorders, anticoagulant therapy, trauma, cocaine abuse.

Treatment of Subarachnoid Hemorrhage

• Primary Goals:

  • Prevent rebleeding

  • Treat complications associated with SAH

• Surgical Intervention:

  • Collapsed aneurysm can be addressed through surgical clipping or endovascular coiling.

Long-term Outcomes

• Mortality Rate: Approximately 20%.

• Neuropsychological Impact: Long-term problems in memory, concentration, psychomotor speed, visuospatial skills, or executive function found in 60-80% of SAH patients.

• Risk Factors for Mortality:

  • Poor clinical grade

  • Advanced age

  • Large aneurysm size

  • History of aneurysm rebleeding

  • Cerebral infarction resulting from vasospasm

  • Global cerebral edema

Differential Diagnosis: Ischemic vs. Hemorrhagic Stroke

• Differentiation Points:

  • Ischemic Stroke: Primarily involves cerebral thrombosis or embolism, often with a history of TIA, slower onset, and headache is rare.

  • Hemorrhagic Stroke (Subarachnoid): Characterized by sudden onset, common severe headache, increased intracranial pressure seen in CT scans with characteristic fluid findings.

• Headache Occurrence: Seldom in ischemic stroke; common and severe in subarachnoid hemorrhage.

Questions for Review

• What are the main clinical manifestations of subarachnoid hemorrhage?

• What are the predilection sites for saccular aneurysms?

• What is the gold standard test for diagnosing subarachnoid hemorrhage?

• What are the potential complications associated with subarachnoid hemorrhage?