What is Digital Subtraction Angiography (DSA) in Neurosurgery
Digital subtraction angiography (DSA) is a catheter-based imaging technique that uses electronic subtraction to display cerebral blood vessels in real-time, free of bony structures, and serves as the gold standard for diagnosing and planning treatment of neurovascular pathology. 1, 2
Technical Principles
DSA works by electronically subtracting pre-contrast images from post-contrast images, allowing near-instantaneous demonstration of vascular anatomy essentially free of bony detail. 3 The technique possesses high contrast sensitivity and can produce arterial images through both intravenous injection and selective arterial catheterization, though the latter provides superior resolution for neurosurgical applications. 3, 4
Clinical Applications in Neurosurgery
Brain Arteriovenous Malformations (AVMs)
DSA with 2D, 3D, and reformatted cross-sectional views is the mandatory investigation before any treatment decision for brain AVMs. 1, 2 The superior spatial and temporal resolution of DSA allows identification of critical angioarchitectural features that predict rupture risk and guide treatment planning, including:
- Feeding artery aneurysms and intranidal aneurysms that significantly increase hemorrhage risk 1, 2
- Large-caliber arteriovenous fistulous connections within the nidus 1, 2
- Venous outflow stenoses that elevate rupture risk 1, 2
- Deep venous drainage patterns associated with higher hemorrhage risk 2
High-frame-rate planar 2D-DSA (≥7.5 frames per second) distinguishes the precise order of vessel filling even in high-flow situations, which is crucial for treatment planning. 1, 2 Vessel-selective catheter-based DSA enables precise identification of individual arterial inputs to the brain AVM. 1, 2
Intracranial Aneurysms
For aneurysms larger than 5 mm, DSA, CTA with 3D reconstruction, and MRA with 3D reconstruction appear roughly equivalent. 1 However, DSA offers diagnostic advantage for detecting small aneurysms less than 3 mm in diameter, where CTA and MRA have lower sensitivity. 1
DSA is recommended as the initial imaging test for intracranial mycotic aneurysms (ICMA), and conventional angiography is reasonable when CTA or MRA results are negative but clinical suspicion remains high. 1 In the acute setting for defining aneurysmal pathology in detail sufficient for treatment, DSA remains the preferred modality. 1
Intraoperative Use
Modern robotic DSA systems installed in hybrid operating rooms allow intraoperative 2D/3D angiography and C-arm-based CT imaging during procedures such as aneurysm clipping and arteriovenous fistula treatment without moving the operating table. 5 This enables immediate verification of surgical results and detection of residual pathology. 5
Advantages Over Non-Invasive Imaging
DSA remains superior to MRA and CTA for identifying relevant angioarchitectural features due to higher spatial and temporal resolution. 1, 2 While MRI offers greater soft tissue anatomical resolution and is useful for identifying eloquent cortex, fusion between 3D-DSA and 3D-volumetric MRI represents the optimal combined technique for localizing vascular malformations and stratifying both natural history risk and treatment risk. 1, 2, 6
Risks and Limitations
DSA is an invasive procedure associated with a small risk (<1%) of complications, including contrast-induced kidney injury or neurological deficits (<0.5%). 1 The procedure involves radiation exposure and risks related to iodine-based contrast agents, including allergic reactions and renal dysfunction. 7
Disadvantages for intracranial studies include poorer spatial resolution compared to modern high-resolution conventional angiography in some contexts, superimposition of vessels, and serious degradation of image quality by patient motion. 4
Modern Variations
Volumetric 3D-DSA and time-resolved 4D-DSA provide structural and combined structural/temporal information that can be reformatted in cross-sectional views to precisely localize pathology relative to surrounding anatomical structures. 1, 2 These advanced techniques offer additional information beyond traditional 2D-DSA while maintaining the fundamental advantages of catheter-based angiography. 1, 2