Cerebral Aneurysms and Subarachnoid Hemorrhage

Introduction and Definitions

• Presenters: Dr. Kelly West, Resident Medical Officer at Nepean Hospital, in conjunction with Associate Professor Behzad Eftakara, Consultant Neurosurgeon at Nepean Hospital.

• Cerebral Aneurysms: Also known as intracranial aneurysms.

• Definition: These are abnormal focal outpouchings of cerebral arteries.

• Anatomical Distribution: Intracranial aneurysms are more common at arterial branch points. They are frequently located along the Circle of Willis and other cerebral arteries.

• Most Common Site: The anterior communicating artery is the most common place for an aneurysm to occur.

Epidemiology and Natural History

• Prevalence: Autopsy studies indicate that between $1\,\text{to}\,5\%$ of adults have intracranial aneurysms.

• Rupture Risk: Most aneurysms are small. Approximately $50\,\text{to}\,80\%$ of all aneurysms do not rupture.

• Multiple Genital Findings: Between $10\,\text{to}\,30\%$ of patients present with multiple aneurysms.

Associated Conditions and Risk Factors

• Vascular Abnormalities: Cerebral aneurysms can be associated with other vascular conditions, such as arteriovenous malformations (AVMs) in the brain.

• Connective Tissue Defects: Aneurysms are commonly caused by defects in connective tissue. Associated disorders include:

  • Autosomal dominant polycystic kidney disease (ADPKD).

  • Fibromuscular dysplasia.

  • Marfan syndrome.

  • Ehlers Danlos syndrome.

Subarachnoid Hemorrhage (SAH) Overview

• Presentation: The majority of aneurysms present clinically with subarachnoid hemorrhage.

• Demographics: SAH is more common in women than in men.

• Peak Incidence: The peak age of incidence is between $55\,\text{to}\,60\,\text{years old}$.

• Impact on Stroke Statistics: Ruptured intracranial aneurysms and SAH account for an estimated $5\,\text{to}\,15\%$ of all stroke cases.

• Mortality and Morbidity:

  • 30-day Mortality rate: $45\%$.

  • Survivor Outcome: Approximately $30\%$ of survivors will experience moderate to severe disability.

  • Total mortality and morbidity associated with the condition are considered quite high.

Clinical Presentation and Physical Examination

• Headache Characteristics:

  • Acute onset of the "worst headache of their life."

  • Clinically described as a "thunderclap headache."

• Sentinel/Warning Headache: This is caused by a small leak from the aneurysm site occurring before a major rupture.

• Early Mortality: Approximately $10\%$ of patients will die before reaching medical attention.

• Examination Findings:

  • Reduced level of consciousness or coma.

  • Severe neurological deficits.

  • Meningism: Includes physical signs such as neck stiffness and photophobia.

  • Focal Neurological Deficits: Such as weakness.

Diagnostic Investigations

• Non-contrast CT Brain:

  • The gold standard investigation for subarachnoid hemorrhage.

  • Sensitivity: Almost $100\%$ within the first $6\,\text{hours}$. It remains $92\%$ sensitive in the first $24\,\text{hours}$. Sensitivity decreases as time passes.

• Lumbar Puncture: This is recommended if there is a strong clinical suspicion of SAH but the CT brain does not show evidence of hemorrhage.

• Angiography (Treatment Planning):

  • Digital Subtraction Angiography (DSA): The most commonly used modality. It involves the digital removal of the skull and soft tissues (brain and face) to isolate the vessels. It can show structures like the basilar tip and Circle of Willis.

  • CT Angiography.

  • MR Angiography.

  • 3D Angiography: Used to visualize specific structures like internal carotid artery branch aneurysms.

Classification and Severity Scales

• World Federation of Neurological Surgeons (WFNS) Scale:

  • A clinical scale used to determine patient prognosis.

  • Based on Glasgow Coma Scale (GCS) and motor deficits.

• Fisher Grade:

  • A radiological grade.

  • Used specifically to indicate the risk of vasospasm.

Complications of Subarachnoid Hemorrhage

• Rebleed:

  • A very common complication.

  • Rate: $2\,\text{to}\,4\%$ of aneurysmal SAHs will recur within the first $24\,\text{hours}$.

  • Approximately $15\,\text{to}\,20\%$ will bleed a second time within the first $2\,\text{weeks}$.

  • Requirement: It is critical to secure the ruptured aneurysm as soon as possible to prevent rebleeding.

• Vasospasm:

  • Thought to be caused by the breakdown of blood products.

  • Can result in ischemia and infarction.

  • Infarction is a major cause of long-term morbidity.

• Hydrocephalus: Identified as another major complication following SAH.

Treatment and Management Options

• Surgical Clipping:

  • Involves a craniotomy where a skin incision is made and a window of the skull is removed.

  • The aneurysm is secured using a titanium clip.

• Endovascular Coiling:

  • A catheter is introduced into the femoral artery and threaded up to the cerebral vessel.

  • A coil is introduced into the aneurysm.

  • The aneurysm is secured by a blood clotting mechanism.

• Endovascular Stenting: Another technique used for securing the aneurysm.

Screening and Surveillance

• General Screening Rule: Indicated for people with two immediate relatives who have had intracranial aneurysms and for all patients with autosomal dominant polycystic kidney disease (ADPKD).

• Management of Incidental Findings: Managing asymptomatic aneurysms is controversial because treatment carries its own risks of morbidity and mortality.

• Decision Factors for Treatment vs. Surveillance:

  • Size and shape of the aneurysm.

  • Changes in the aneurysm over time.

  • Patient factors: Smoking status, family history, and history of prior subarachnoid hemorrhage.

• Symptomatic Presentation: Patients with symptoms of compression, such as cranial nerve palsy or brainstem dysfunction, carry an increased risk of rupture and should be evaluated and treated promptly.