Imaging

Intracranial aneurysm

Preliminary Diagnosis: Intracranial Aneurysm

I. What imaging technique is first-line for this diagnosis

  • 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

  • Has high diagnostic accuracy for intracranial aneurysms

  • Can be performed quickly, thus limiting the chance of patient motion artifact resulting in a nondiagnostic exam

  • Preferred imaging modality for subarachnoid hemorrhage, a potential complication of aneurysm

Disadvantages

  • Uses ionizing radiation

  • Small number of patients will have a false negative CTA

III. What are the contraindications for the first-line imaging technique?

  • Pregnancy is a contraindication to CT.

  • Administration of IV contrast requires good renal function, generally a creatinine <1.7.

IV. What alternative imaging techniques are available?

  • MRI/MRA of the brain with and without intravenous (IV) contrast

  • 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

  • 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

  • Relatively lengthy exam that requires patient cooperation to minimize motion artifact

  • Prone to artifacts that may make aneurysms more difficult to diagnose

  • 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

  • Significantly more expensive compared to CT

Conventional angiography

Advantages

  • Gold standard for diagnosis or exclusion of intracranial aneurysms

  • Allows possibility of both diagnosis and treatment (e.g., aneurysm coiling)

  • Can assess for collateral circulation in pretreatment planning

Disadvantages

  • Invasive procedure that requires arterial access (usually via the femoral artery)

  • 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

  • Contraindicated in patients with non-MR compatible metallic implants or foreign bodies

Conventional angiography

  • Contraindicated in patients who are coagulopathic (INR >1.6 and/or platelets <50,000)

  • Contraindicated in patients with poor renal function

  • Contraindicated in patients with uncontrolled hypertension

  • Contraindicated in patients with a contrast allergy or who are pregnant

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