Neurology · Cerebrovascular Disease
The facts most likely to be tested
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Autosomal Dominant Polycystic Kidney Disease (ADPKD) and Ehlers-Danlos syndrome are the most significant genetic associations with saccular (berry) aneurysms.
Cigarette smoking and uncontrolled hypertension are the two most critical modifiable risk factors for the development and growth of intracranial aneurysms.
Posterior communicating artery (PCOM) aneurysms classically present with an ipsilateral CN III (oculomotor) nerve palsy, characterized by a down-and-out eye and a dilated, non-reactive pupil.
Digital Subtraction Angiography (DSA) remains the gold standard for the definitive diagnosis and anatomical characterization of cerebral aneurysms.
Magnetic Resonance Angiography (MRA) or CT Angiography (CTA) are the preferred non-invasive screening modalities for patients with a high-risk family history or associated genetic syndromes.
Surgical clipping or endovascular coiling is indicated for unruptured aneurysms based on size, location, and patient-specific risk factors to prevent subarachnoid hemorrhage (SAH).
Ophthalmic artery and anterior communicating artery (ACOM) aneurysms are common locations that may cause visual field deficits or bitemporal hemianopsia due to compression of the optic chiasm.
Vignette unlocked
A 42-year-old female with a history of ADPKD presents to the clinic for a routine follow-up. She reports no headaches, visual changes, or focal neurological deficits. On physical examination, her blood pressure is 155/95 mmHg. A screening MRA of the brain is performed, which reveals a 6 mm saccular aneurysm at the junction of the internal carotid artery and the posterior communicating artery.
Which of the following physical exam findings would be most consistent with an expansion of this specific aneurysm?
Ipsilateral ptosis and a dilated, non-reactive pupil
The vignette tests the association between ADPKD and PCOM aneurysms, which frequently compress the oculomotor nerve (CN III), leading to the classic triad of ptosis, ophthalmoplegia, and pupillary dilation.
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Etiology / Epidemiology
Associated with ADPKD, Ehlers-Danlos syndrome, and smoking. Most are saccular (berry) aneurysms.
Clinical Manifestations
Usually asymptomatic; large aneurysms cause cranial nerve palsies (CN III) or mass effect.
Diagnosis
Magnetic resonance angiography (MRA) or CT angiography (CTA) are the diagnostic tests of choice.
Treatment
Surgical clipping or endovascular coiling for high-risk lesions; observation for small, low-risk aneurysms.
Prognosis
Risk of rupture correlates with size >7mm and location in the posterior circulation.
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Epidemiology & Etiology
Prevalence is higher in patients with autosomal dominant polycystic kidney disease (ADPKD) and coarctation of the aorta. Major modifiable risk factors include chronic hypertension and tobacco use. Female gender and advanced age are non-modifiable risk factors.
Pertinent Anatomy
Most aneurysms occur at the Circle of Willis bifurcations. The anterior communicating artery is the most common site, followed by the posterior communicating artery. Aneurysms near the posterior communicating artery frequently compress the oculomotor nerve (CN III).
Pathophysiology
Aneurysms develop due to defects in the tunica media of arterial walls. Hemodynamic stress at vessel bifurcations leads to progressive dilation. Rupture results in subarachnoid hemorrhage, causing sudden, severe intracranial pressure elevation.
Clinical Manifestations
Most unruptured aneurysms are incidental findings. Large lesions may present with cranial nerve III palsy (ptosis, mydriasis, 'down and out' eye) due to compression. Red flag symptoms include sudden onset of 'thunderclap' headache, suggesting aneurysmal rupture.
Diagnosis
CT angiography (CTA) is the initial study of choice for rapid detection. Magnetic resonance angiography (MRA) is preferred for screening high-risk populations to avoid radiation. Digital subtraction angiography (DSA) remains the gold standard for definitive anatomical mapping.
Treatment
Management is based on the International Study of Unruptured Intracranial Aneurysms (ISUIA) criteria. Surgical clipping or endovascular coiling is indicated for aneurysms >7mm or those in the posterior circulation. Antiplatelet therapy may be required post-coiling to prevent thromboembolic events.
Prognosis
Annual rupture risk is low for small (<7mm) anterior circulation aneurysms but increases significantly with size >7mm, and especially >10mm. Patients require serial imaging to monitor for growth if managed conservatively.
Differential Diagnosis
Pituitary adenoma: bitemporal hemianopsia
Cavernous sinus thrombosis: ophthalmoplegia and chemosis
Migraine: transient neurological deficits
Arteriovenous malformation: presence of a vascular bruit
Tension headache: lack of focal neurological deficits