1 ) Cerebral aneurysm — institutional practice varies, with many surgeons now operating based on CTA or less often MRA data alone. Our practice is to obtain a diagnostic angiogram prior to consideration of aneurysm treatment, endovascular or surgical.
2 ) Brain Arteriovenous Malformation (AVM) — pretty much all AVMs visualized on MRI or CT are then evaluated by catheter angiography.
3 ) Dural Arteriovenous Fisula — CT and MR are still quite limited in their capability to detect fisulas (dynamic MRA/CTA is changing this, but in my opinion are not yet sensitive and reliable and safe enough[from CTA radiation exposure standpoint]).
4 ) Cryptogenic Intracerebral Hemorrhage — patients with atypical demographics, unusual hemorrhage locations, and other potentially non-standard situations should be considered for angiography — small fistulas, AVMs, venous thromboses, mycotic aneurysms, are among etiologies which may not be adequately excluded by CT or MR techniques. A particular kind of common cryptogenic hemorrhage is CTA-negative subarachnoid hemorrhage. At our institution, all subarachnoid hemorrhage patients with no etiology found on CT angiography are referred for catheter angiography. Diagnostic yield in these cases varies with hemorrhage pattern and other factors, but on the whole at least 10% of patients are thus found to have a reason for their bleeding.
5 ) Dissections — many cervical carotid and vertebral dissections can now be adequately evaluated with CT and MR. Most dissections do not lead to a neurologic event, such as stroke, and might come to medical attention as a result of pain. In our practice, any dissection with a neurologic event, such as TIA or stroke, is indication for angiogrpahic evaluation — see below. Another reason may be a high-grade dissection with suspicion of inadequate collaterals based on CT or MR techniques — evaluation of collateral potential based on CT or MR requires expert knowledge of neurovascular anatomy, which usually implies consultation with a highly experienced neuroradiologist, vascular neurologist, or vascular neurosurgeon.
6 ) High-grade intracranial stenosis — at least requires a consultation with a neuro-angiographer. The issues of intracranial stenosis are complex, both in terms of pathophysiology and adequate management. Practitioners dealing with intracranial stenoses should be familiar with results of the SAMPRIS trial, which demonstrated overall superiority of medical management over intracranial stenting for patients with symptomatic intracranial stenosis. Individual patients may, nevertheless benefit from an angiographic evaluation based on unique considerations.
7 ) Acute stroke — not technically a referral for angiography, but rather for angiography and stroke treatment, such as thrombolysis or thrombectomy (clot removal). Recent substantial advances in mechanical clot retrieval have greatly increased the technical success of thrombectomy. Translating this into clinical improvement is a complex process which requires public education, perfection of triage and logistics, etc. Ultimately, most patients with ischemic stroke are, unfortunately, still not eligible for interventional stroke treatment or intravenous t-PA.
8 ) Cerebral vasculitis — remains a difficult diagnosis to make. Multiple subcortical strokes are the hallmark of cerebral vasculitis, either primary or as part of a systemic disorder, such as Lupus. Referral depends on practice patterns of local rheumatologists, neurologists, and other physicians dealing with this difficult disease. It is possible to have a normal angiogram and still suffer from cerebral vasculitis, so that a normal angiogram does not exclude the diagnosis. On the other hand, if vasculitis treatment will be offered regardless of angiographic findings, there may be no reason to perform the angiogram, given that compelling evidence for vasculitis exists based on other considerations.
9 ) Preoperative Tumor Embolization — also not technically an angiogram, but rather angiogram and embolization. Vascular neoplasms such as meningiomas, renal cell carcinomas, glomus tumors, JNAs, among others, can be de-vascularized by particle embolization prior to surgical resection to limit intraoperative blood loss and improve the overall success and safety of subsequent surgery.
10 ) Cerebral venous thrombosis — a treacherous condition, often requiring high level of suspicion, which is most often made based on non-invasive imaging such as CT and MR. Suspected cases of cortical venous thrombosis or those considered for catheter – based thrombolysis require an angiogram.
Additional procedures coupled with cerebral angiography include Wada activation testing (usually performed for various surgical considerations), venous sinus sampling (pituitary issues), venous sinus stenosis (occasionally associated with pseudotumor cerebri, and possibly requiring treatment), among others.
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