Conventional Angiography & Cranial–Spinal Shunts

Ask a Question That Angiography Can Answer

Digital subtraction angiography (DSA) removes background structures from contrast images to show vessels with high spatial and temporal detail. It can display arterial filling, capillary transit, early venous drainage, collateral routes, and lesion anatomy. CT and MR angiography are less invasive and often appropriate first studies, but DSA may resolve a specific unanswered question or support treatment in the same session.

The blueprint includes conventional cerebral angiography, vascular anomalies, symptomatic unruptured aneurysms, and cranial and spinal dural fistulas. Do not order DSA reflexively for every abnormal noncontrast scan. Define whether the question is an occult aneurysm, a high-flow shunt, venous drainage architecture, vasospasm, dissection, or an intervention plan. The expected benefit must justify procedural risk.

Read the Temporal Phases

For an aneurysm, define location, neck, dome, relation to branches, irregularity, and features relevant to treatment. A new pupil-involving third-nerve palsy with a compatible aneurysm raises concern for symptomatic compression and possible instability. Even without subarachnoid blood on CT, urgent neurovascular evaluation is needed. Management of an unruptured lesion depends on symptoms, anatomy, patient factors, rupture risk, and treatment risk rather than a single size threshold.

After an angiogram-negative SAH, further investigation depends on the blood pattern, quality and completeness of the first studies, clinical findings, and the specialist plan. A diffuse aneurysmal pattern raises greater concern for an occult lesion than a strictly perimesencephalic pattern. Do not represent one fixed repeat-imaging day as a universal rule for every patient.

AVMs and Cranial Dural Fistulas

A brain AVM has a nidus connecting feeding arteries to draining veins without an ordinary intervening capillary network. DSA helps define feeders, associated aneurysms, and superficial or deep drainage. The Spetzler–Martin scale estimates microsurgical risk and is not itself a universal directive to operate. Prior rupture, symptoms, location, age, and treatment options all influence decisions.

A dural arteriovenous fistula is a shunt between dural arterial supply and venous structures. Venous drainage is central to risk: cortical venous reflux or direct cortical drainage can cause venous congestion, hemorrhage, and neurologic deterioration. A lesion draining without cortical reflux may have a different natural history and symptom burden. The angiographic study must identify the shunt and drainage sufficiently to plan safe disconnection while preserving necessary normal venous pathways.

Classification systems describe different aspects of this anatomy. Avoid treating every Borden and Cognard category as an exact one-to-one correspondence. Cognard type V includes spinal perimedullary venous drainage, a reminder that a cranial shunt may have spinal manifestations. Clinical urgency is determined by drainage, symptoms, hemorrhage, and the specialist assessment.

Spinal Dural AV Fistula

Spinal dural AV fistula can cause progressive venous congestive myelopathy, often with gait difficulty, leg weakness, sensory change, and bladder dysfunction. Symptoms may fluctuate before becoming steadily worse. MRI can show longitudinal cord edema and abnormal perimedullary vessels, but findings are not always obvious. The syndrome can be misdiagnosed as inflammatory myelitis or degenerative spine disease.

Catheter spinal angiography is the definitive anatomic investigation when the suspicion is sufficient. It can require evaluation of multiple segmental vessels by an experienced team. An incomplete negative study does not provide the same reassurance as an appropriately complete investigation. Treatment aims to disconnect the abnormal shunt and venous drainage through selected endovascular or surgical methods. Delay can permit ongoing cord injury, so progressive unexplained myelopathy with vascular clues warrants reassessment.

Procedural Safety and Post-Procedure Deterioration

Before DSA, assess access, hemostasis, antithrombotic exposure, renal function, contrast-reaction history, airway and transport risks, and intracranial stability. Sedation must permit safe imaging while preserving systemic perfusion. Document a baseline neurologic and limb examination when feasible. A blood-pressure fall during the procedure can harm collateral-dependent tissue even when the catheter images are technically satisfactory.

Afterward, evaluate new focal deficits promptly for thromboembolism, dissection, hemorrhage, or contrast-related encephalopathy rather than dismissing them as routine sedation. Inspect the access site and distal perfusion. Groin or flank pain, falling pressure, or an unexplained hemoglobin decline can suggest access bleeding or retroperitoneal hemorrhage. Contrast-associated kidney risk deserves assessment, but it should not automatically delay a life-saving procedure.

A useful vignette combines progressive leg dysfunction, cord edema, and perimedullary flow voids. Recognizing a possible spinal fistula changes the investigation and treatment path. Another combines a new third-nerve palsy and an unruptured aneurysm; the absence of visible SAH does not make the finding an elective reassurance problem.

Sources checked October 17, 2026: ABPN detailed outline and AHA/ASA aSAH guideline.