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The progressive development of microcatheters, guidewires, coils and stents capable of intracranial use paralleled by higher resolution and 3D angiographic imaging systems has led to the extension of diagnostic cerebral angiography into this new subspecialty which combines aspects of treatment with diagnosis in the same procedure.
As is directly complements, extends, and can sometimes (e.g. GDC; stents) replace neurosurgery, it is sometimes also called Endovascular Neurosurgery. Thus at Dalcross the Interventional Neuroradiology Unit is a collaboration including Neurosurgery (Prof Michael Morgan) and Neuroradiologists (Drs Tim Harrington, Verity Grinnell, Ken Faulder and William Sorby) with referrals primarily to Prof Morgan for consultation by the Unit.
Interventional Neuroradiological Techniques comprise:
- 3D Cerebral Angiography
- Cerebral aneurysm occlusion with GDC coils
- Cerebral vasospasm angioplasty with balloon and/or Papaverine
- Vertebro-basilar arterial stenosis angioplasty/stenting
- Extra-cranial carotid arterial stenosis angioplasty/stenting
- Pre-operative embolisation of vascular head, neck, spinal tumours
- Pre-operative embolisation of AVM/DAVF
- Embolisation of carotid-cavernous fistulae
- Test balloon occlusion of carotid/vertebral arteries pre-operatively to assess cerebrovascular collateral blood flow
- Thrombolysis of acutely thrombosed cerebral vessels
3D Cerebral Angiography
While the small vessel resolution of Digital Subtraction Angiography has improved enormously in recent years, complex aneurysmal or AVM, etc anatomy can still only be visualised mentally from separate A-P, lateral, oblique views.
3D angiography acquires multiple views of the cerebral vessels through a 180„a arc during contrast injection. A computer algorithm then reconstructs these vessels in the same manner at CTA/MRA, but with much higher resolution of small vessel detail.
These images can then be rotated into any plane some of which (e.g. basal) are impossible to achieve directly.
Thus the precise size and shape of a cerebral aneurysm and its relation to parent vessels can be clearly shown to decide if it is suitable for endovascular GDC embolisation or surgical clipping.
Similarly during aneurysm embolisation the correct positioning of GDC coils within the fundus, and the exclusion of incorrect coil position within parent arteries can be more accurately assessed before coil detachment.
Cerebral Aneurysm Occlusion with GDC coils
Surgical exposure and clipping of cerebral aneurysms is the mainstay of treatment. However since 1991, Guglielmi Detachable Coil (GDC) embolisation of suitable cerebral aneurysms has been developed in many international Interventional Neuroradiology Units with progressive improvement in results with experience, with new coils and catheters, and now with the availability of 3D angiography providing unparalleled accuracy in demonstration of aneurysm size and shape and coil position. Currently GDC embolisation of cerebral aneurysms is considered if :
- Aneurysm size and shape is suitable (i.e. fundus <10mm; neck 4mm)
- Aneurysm site/parent vessel anatomy is suitable (i.e. V-Basilar; A.Com; P.Com may be suitable; MCA usually unsuitable)
- Patients in which surgical clipping carries a higher risk than usual (i.e.
- High Hunt and Hess grades
- Co-morbidities/anaesthetic risk
- Vasospasm
- Aneurysm site difficult for clipping)
Endovascular Treatment of Cerebral Vasospasm
Cerebral vasospasm remains a significant cause of disability or death following successful surgical clipping of aneurysms despite prophylactic calcium channel blockers and conventional ˇĄtriple Hˇ¦ therapy.
Papaverine Angioplasty
Where the clinical suspicion of cerebral vasospasm post SAH is confirmed by diagnostic cerebral angiography, Papaverine, a powerful but transient vasodilator, can be directly injected by slow intra-arterial infusion into internal carotid and/or vertebral arteries. This is usually able to reverse the vasospasm with visible enlargement of the major arteries, and reduced arterial-venous transit time indicating improved small vessel perfusion.
Balloon Angioplasty
The recent development of soft, small flexible balloon micro-catheters now permits direct angioplasty of the larger vasospastic intracranial arteries (ICA, MCA, Vertebro-Basilar) when Papaverine angioplasty is transient or ineffective.
Increasingly these techniques are used in a complementary fashion with the low risk Papaverine infusion being used initially, with balloon angioplasty for recurrent or unresponsive vasospasm.
Tony P, Smith MD, David S. Enterline MD. Endovascular Treatment of Cerebral Vasospasm.
JVIR 2000; 11: 547-559
Angioplasty/Stent of Vertebro-Basilar Stenoses
Vertebro-Basilar Ischaemia due to basilar artery and/or vertebral stenoses/occlusions has conventionally been treated by long term anticoagulation alone, as surgical re-vascularisation was usually not feasible.
Progression of these atheromatous lesions frequently caused severely disabling stroke or death.
The recent development of smaller more flexible arterial stents, together with more potent antiplatelet therapy (Clopidogrel, abciximab) now permits angioplasty/stenting as an effective means of re-vascularisation of the posterior cerebral circulation.
Extracranial Carotid Stenting
Carotid Stenting is now considered best used where CEA has a higher risk
- Recurrent stenosis after CEA
- Post Radiotherapy carotid stenoses
- High carotid bifurcation/stenosis
- Intra-petrous internal carotid stenosis
- Medical co-morbidities
Carotid stenting may also be used for management of internal carotid artery dissection/aneurysm or fibromuscular arterial dysplasia.
Pre-operative Embolisation of Vascular Head, Neck and Spinal Tumours
Some highly vascular tumours increase surgical risk from excessive blood loss and/or obscuring anatomical landmarks during excision.
The availability of microcatheters and guides now permits safer subselective catheterisation of the vascular pedicles of such tumours with progressive de-vascularisation by use of Ivalon or other embolic materials.
Skull base meningioma, glomus jugulare, and vascular vertebral metastases (e.g. renal carcinoma) are the most suitable for these techniques.
Cloft HJ, Dion JE. Pre-operative and palliative embolization of vertebral tumors.
Neuroimaging Clin N Am 2000 Aug 10 (3)569-78.
Pre-operative Embolisation of Intracranial Arterio-Venous Malformations and Dural Anterior Venous Fistulae
The development of a variety of flexible and atraumatic microcatheters and guides now permits increasingly subselective catheterisation of intracranial vessels supplying AVM/DAVF for more accurate demonstration of their anatomy pre-operatively.
Although attempted treatment by embolisation alone using a variety of embolic agents (Ivalon, alcohol, tissue glue) has been shown to be inadequate, endovascular embolisation of selected pedicle pre-operatively enhances the safety and completeness of surgical excision.
Vinuela F et al. Combined endovascular embolization and surgery in the management of cerebral arteriovenous malformations: Experience with 101 cases. J Neurosurg 75: 856-864, 19991.
Embolisation of Carotid-Cavernous Fistula
Direct high flow C/C fistula, often post traumatic in association with skull base fracture, may rapidly progress to blindness and/or cerebral haemorrhage. Because of their position, neurosurgical management is usually limited to ligation of the internal carotid artery both intra-cranially and extracranially, with associated risks of stroke if collateral circulation is inadequate.
Thus the endovascular treatment by balloon occlusion of the fistula and/or micro catheter and fibred coil occlusion of the cavernous sinus via the petrosal sinus, is the preferred treatment, as the internal carotid artery can be preserved.
Gobin YP, Duckwiler GR, Vinuela F. Direct arterio-venous fistulas (carotid-cavernous and vertebral-venous). Diagnosis and intervention. Neuromiaging Clin N Am 1998 May; 8 (2): 425-43
Test Occlusion of Carotid Arteries Pre-operatively
Using a non-detachable balloon inflated in the carotid artery under heparinisation and clinical, EEG, and SPECT control, the adequacy of Circle of Willis collateral blood supply can be assessed pre-operatively when carotid resection is planned.
Thrombolysis of acutely Thrombosed Cerebral Vessels
The use of intra-arterial thrombolysis in acute (0-3 hour) stroke with MCA/ICA occlusion is being studied at international units and remains experimental until the outcomes/complications relative to conventional anti-coagulation management have been assessed.
However intra-arterial thrombolysis in acute post-operative extra/intra-cranial vein bypass surgery, and in the treatment of embolic complications of endovascular stent/CABG can reperfuse ischaemic brain and reduce the severity or extent of cerebral damage.
Intravascular thrombolysis of venous sinus thrombosis can also be performed with microcatheters reducing venous oedema and infarction and improving patient outcomes.
Cronqvist M et al. Local intra-arterial fibrinolysis of thromboemboli occurring during endovascular treatment of intra-cerebral aneurysm: A comparison of anatomic results and clinical outcome. AJNR Am J Neuroradiol 19: 157-165, 1998
References
- Morgan MK, Grinnell V, Little NS et al. Successful treatment of an acute thrombosis of an intra-cranial vertebral endarterectomy with Urokinase. Neurosurgery 35: 978-981, 1994
- Morgan MK, Day MJ, Little N, Grinnell V, Sorby W: The use of intra-arterial Papaverine in the management of vasospasm complicating the resection of arterio-venous malformations of the brain. J Neurosurg 82:296-299, 1995.
- Morgan MK, Sekhon L, Halcrow S, Grinnell V, Sorby W : Effective management of cerebral vasospasm with balloon angioplasty after failed Papaverine angioplasty. Journal of Clinical Neuroscience 3:162-165, 1996
- Morgan MK, Halcrow S, Sorby W, Grinnell V: Outcome of aneurysmal subarachnoid haemorrhage following the introduction of Papaverine angioplasty. Journal of Clinical Neuroscience 3: 139-142, 1996
- Morgan MK. Drummond K, Sorby W, Grinnell V: Surgical management of dural arterio-venous malformations of the cranium. J Clin Neuroscience 5: 318-322, 1998
- Sekhon LHS, Morgan MK, Sorby W, Harrington T, Grinnell V. Combined endovascular stent implantation and endovascular coil placement for the treatment of wide necked vertebral artery aneurysm. Neurosurgery 43: 380-384 1998
- Brennan JW, Morgan MK, Sorby W, Grinnell V: Recurrent stenosis of common carotid to intracranial internal carotid interposition saphenous vein bypass graft due to intimal hyperplasia treated with endovascular stent placement. J Neurosurgery 90:571-574, 1999
- Morgan MK, Jonker B, Finfer S, Harrington T, Dorsch NW. Aggressive management of aneurysmal subarachnoid haemorrhage based on a Papaverine angioplasty protocol. J Clin Neuroscience 7:277-380, 2000
- Morgan MK, Zurin AAR, Harrington T, Little N: Changing role for per-operative embolisation in the management of arterio-venous malformations of the brain. Journal of Clinical Neuroscience 7: 527-530, 2000.
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