What Cerebral CT Angiography Diagnoses
Cerebral CT angiography (CTA) is a rapid, highly sensitive vascular imaging technique that diagnoses aneurysms, arteriovenous malformations, arterial dissections, intracranial stenosis/occlusions, vasculitis, and other cerebrovascular abnormalities with sensitivity and specificity exceeding 90% for most vascular lesions. 1
Primary Diagnostic Capabilities
Aneurysms
- CTA detects cerebral aneurysms with 96.5% sensitivity for all sizes and 98.4% sensitivity for aneurysms >3mm 2
- Sensitivity decreases for aneurysms <3mm or those adjacent to skull base bone due to artifact 2, 3
- Essential when subarachnoid hemorrhage is present in basal cisterns or sylvian fissure 2
Arteriovenous Malformations (AVMs)
- CTA correctly identifies 93.75% of AVMs measuring <3cm 4
- Detects deep venous drainage with 100% sensitivity 4
- Identifies AVMs in eloquent brain areas with 100% sensitivity 4
- Detects 86.6% of AVM-associated aneurysms, though less sensitive for intranidal (77.78%) and flow aneurysms (66.67%) 4
Arterial Dissection
- CTA demonstrates intimal flaps, vessel narrowing, and pseudoaneurysm formation in cervicocranial dissections 1
- Provides rapid noninvasive assessment of both extracranial and intracranial vessels 1
Large Vessel Occlusion (LVO) and Stenosis
- CTA rapidly identifies intracranial arterial occlusions for endovascular thrombectomy eligibility 1
- Evaluates intracranial atherosclerosis and steno-occlusive disease 1
- Assesses extracranial carotid and vertebral artery stenosis 1
Vasculitis and Vasculopathy
- CTA provides noninvasive assessment of large-to-medium vessel vasculitis 1, 5
- Shows arterial beading, alternating constriction/dilatation, and segmental narrowing 5
- Limited sensitivity for small-vessel vasculitis, which requires catheter angiography or biopsy 1, 5
Prognostic Applications
CTA Spot Sign
- Identifies contrast extravasation within hematomas, predicting expansion risk and clinical deterioration 1, 2
- Associated with poor outcomes in intracerebral hemorrhage 1, 2
Clinical Context for Use
Intracerebral Hemorrhage (ICH)
- Indicated for lobar hemorrhages, superficial hemorrhages, or hemorrhages in younger patients without hypertension 2
- Essential for isolated intraventricular hemorrhage without obvious cause 2
- In one series, CTA detected vascular abnormalities in 42% of ICH patients (28% aneurysms, 11% AVMs) 6
Subarachnoid Hemorrhage (SAH)
- First-line vascular imaging after noncontrast CT confirms SAH 1
- When CTA is negative in confirmed SAH, hemorrhage pattern guides need for catheter angiography 3
- Digital subtraction angiography identifies additional pathology in 13% of CTA-negative SAH cases 7
Pediatric Hemorrhagic Stroke
- Particularly important as 48% of pediatric hemorrhagic strokes result from arteriovenous shunts 2
- CTA provides rapid assessment without sedation required for MRA 1
Important Limitations
Technical Constraints
- Overlying bone at skull base creates artifacts that obscure small aneurysms 2, 3
- Metallic coils, clips, or stents cause streak artifacts limiting post-treatment surveillance 2
- Quality depends heavily on radiologist experience and proper technique 3
- Vessel tortuosity decreases specificity and may cause misinterpretation 3
Diagnostic Gaps
- Cannot detect small-vessel vasculitis (requires catheter angiography or biopsy) 1, 5
- May miss vascular lesions compressed by acute hematoma 6
- In ICH patients, 58% have normal CTA or findings unrelated to hemorrhage 6
When to Proceed to Catheter Angiography
- CTA-negative SAH with diffuse or perimesencephalic pattern requires digital subtraction angiography 7
- Suspected vasculitis with negative or equivocal CTA 1, 5
- Detailed characterization needed before surgical/endovascular intervention 1
- Follow-up angiography identifies additional 4% of aneurysms missed on initial studies 7