Note: Youmans and Winn Neurological Surgery is not in this library's catalog. The gist below is drawn from Bradley & Daroff's Neurology in Clinical Practice (a peer neurology/neurosurgery reference), which covers the same intracranial aneurysm content in comparable depth.

Intracranial Aneurysms - Gist (Bradley & Daroff's Neurology)

Definition

Epidemiology

• Incidence of aSAH: 2-16 per 100,000/year worldwide
• At least 1/4 of admitted patients die
• Half of survivors have permanent neurological deficit
• Only 1/3 return to prior work
• Prevalence of unruptured aneurysms: ~3-5% of general population
• Peak rupture age: 40-60 years, more common in women

Morphological Types

Pathogenesis (Saccular)

• Intracranial arteries lack external elastic lamina (disappears at cavernous ICA segment and vertebral arteries at skull entry)
• Key step: degeneration of tunica media + internal elastic lamina at bifurcation points under chronic hemodynamic stress
• Rupture risk driven by: wall stress, size, location, hypertension, smoking
• In children: may be congenital rather than degenerative

Size Classification

Location (Anterior > Posterior Circulation)

Associated Conditions (Risk Factors)

• Hypertension, smoking, heavy alcohol use
• Connective tissue disorders: Ehlers-Danlos type IV, Marfan syndrome
• Polycystic kidney disease (ADPKD - 4-10x higher prevalence)
• Coarctation of aorta
• Family history (1st-degree relative with aneurysm)
• Atherosclerosis, trauma, neoplasm, radiation, drug abuse, vasculopathy, moyamoya disease

Clinical Presentation

Ruptured Aneurysm (aSAH)

• "Thunderclap headache" - sudden, severe, "worst headache of my life", maximal at onset
• Nuchal rigidity, photophobia, nausea/vomiting
• Altered consciousness (from raised ICP or direct brain injury)
• Focal deficits depending on location (e.g., CN III palsy - posterior communicating artery aneurysm)

Unruptured Aneurysm (Incidental or Mass Effect)

• Often asymptomatic - found incidentally on CTA/MRA
• Large aneurysms may compress adjacent structures:
  • PComm aneurysm → ipsilateral CN III palsy (ptosis, mydriasis, "down and out" eye)
  • Ophthalmic artery aneurysm → visual field defects

Grading Scales

• Grade I: Asymptomatic or mild headache
• Grade II: Moderate/severe headache, nuchal rigidity, no deficit
• Grade III: Drowsiness, mild deficit
• Grade IV: Stupor, hemiparesis
• Grade V: Deep coma, decerebrate posturing

• Group 1: No blood
• Group 2: Thin diffuse layer < 1 mm
• Group 3: Localized clot or layer ≥ 1 mm (highest vasospasm risk)
• Group 4: Diffuse SAH with intraparenchymal/intraventricular clot

Diagnosis

Imaging

1. Non-contrast CT - first-line; sensitivity ~100% in first 3 days (decreases over time)
2. Lumbar puncture - if CT negative but clinical suspicion high; look for xanthochromia (appears 2 hours post-bleed, lasts weeks) + elevated RBCs
3. CTA - fast, can visualize aneurysm directly; preferred for initial evaluation and screening of unruptured aneurysms
4. MRA - least invasive; good for screening; lower sensitivity for slow-flow aneurysms; not ideal for acute SAH
5. Digital Subtraction Angiography (DSA) - gold standard; mandatory if CT + CTA both negative in suspected SAH; also used pre-treatment planning

Treatment

Unruptured Aneurysms

• Metal clip placed across the aneurysm neck to isolate it from circulation
• Preferred for MCA aneurysms (accessible, often wide-necked)
• Durable; low recurrence

• Microcatheter placed in aneurysm dome; platinum coils packed to induce thrombosis
• Now more common in the US than clipping
• Better for basilar tip and paraclinoid aneurysms (hard surgical access)
• Success depends on anatomy (neck width) rather than location
• Adjuncts: balloon-assisted coiling, stent-assisted coiling for wide-necked aneurysms
• Flow diversion (Pipeline Embolization Device): redirects blood flow away from aneurysm; excellent for large/giant fusiform aneurysms

Ruptured Aneurysms (aSAH Management)

• Early aneurysm repair (clipping or coiling) within 24-72 hours to prevent rebleeding
• ISAT trial: endovascular coiling vs. neurosurgical clipping - coiling showed better outcomes at 1 year for eligible aneurysms

Complications After aSAH

Rebleeding

• Highest risk in first 24 hours (up to 15%); 40% within first month if untreated
• Catastrophic - drives urgency of early repair

Vasospasm and Delayed Cerebral Ischemia (DCI)

• Occurs 4-14 days post-SAH
• Result of oxyhemoglobin-induced arterial spasm
• "Triple H" therapy (historically): Hypertension, Hypervolemia, Hemodilution (now evolved toward induced hypertension)
• Nimodipine (oral calcium channel blocker) is standard - reduces DCI and improves outcomes
• Transcranial Doppler and angiography used to monitor

Hydrocephalus

• Acute: CSF outflow obstruction from blood in subarachnoid space
• Treated with external ventricular drain (EVD) or lumbar drain

Hyponatremia

• Cerebral salt wasting or SIADH; worsens vasospasm risk

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