Preliminary Diagnosis: Intracranial Aneurysm
I. What imaging technique is first-line for this diagnosis
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CT angiogram (CTA). However, a non-contrast head CT should be performed first, followed by CTA, which requires IV contrast.
II. Describe the advantages and disadvantages of this technique for diagnosis of an intracranial aneurysm.
Advantages
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Has high diagnostic accuracy for intracranial aneurysms
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Can be performed quickly, thus limiting the chance of patient motion artifact resulting in a nondiagnostic exam
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Preferred imaging modality for subarachnoid hemorrhage, a potential complication of aneurysm
Disadvantages
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Uses ionizing radiation
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Small number of patients will have a false negative CTA
III. What are the contraindications for the first-line imaging technique?
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Pregnancy is a contraindication to CT.
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Administration of IV contrast requires good renal function, generally a creatinine <1.7.
IV. What alternative imaging techniques are available?
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MRI/MRA of the brain with and without intravenous (IV) contrast
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Conventional cerebral angiography
V. Describe the advantages and disadvantages of the alternative techniques for diagnosis of an intracranial aneurysm.
MRI/MRA of the brain with and without (IV) contrast
Advantages
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Surrounding soft tissue anatomic detail is depicted better than on CT, which may allow better visualization of structures affected by the aneurysm (e.g., cranial nerves).
Disadvantages
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Relatively lengthy exam that requires patient cooperation to minimize motion artifact
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Prone to artifacts that may make aneurysms more difficult to diagnose
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IV contrast requires adequate renal function (GFR >60), although decision to administer contrast can be made on a case-by-case basis in patients with GFR of 30 to 60
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Significantly more expensive compared to CT
Conventional angiography
Advantages
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Gold standard for diagnosis or exclusion of intracranial aneurysms
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Allows possibility of both diagnosis and treatment (e.g., aneurysm coiling)
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Can assess for collateral circulation in pretreatment planning
Disadvantages
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Invasive procedure that requires arterial access (usually via the femoral artery)
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Associated with significant morbidity and mortality, particularly with aneurysm treatment
VI. What are the contraindications for the alternative imaging techniques?
MRI/MRA with and without IV contrast
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Contraindicated in patients with non-MR compatible metallic implants or foreign bodies
Conventional angiography
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Contraindicated in patients who are coagulopathic (INR >1.6 and/or platelets <50,000)
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Contraindicated in patients with poor renal function
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Contraindicated in patients with uncontrolled hypertension
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Contraindicated in patients with a contrast allergy or who are pregnant
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