INTRODUCTION
The relatively recent advent of sophisticated imaging techniques such as CT and MR has dra- matically reduced the demand for conventional invasive selective cerebral angiography in radio- logical diagnosis. Despite the fact that conven- tional angiography is now considered comple- mentary to other techniques in neurological emergencies, it has been shown not to be com- pletely replaceable because there are certain questions that angiography alone can answer.
In recent years, there has been a return to the use of angiography based on the improvement in the technique’s safety, speed and sophistication (e.g., hard- and software improvements, atrau- matic catheterization materials, and new low os- molarity contrast agents), and on the progres- sively increasing experience of vascular interven- tional radiology treatment techniques (8). This last factor has led to angiography being consid- ered as having a dual purpose: an instrument used in both diagnosis and therapy.
CLINICAL INDICATIONS
The clinical indications for emergency an- giography are cerebral ischaemia and haem-
orrhage, as well as some forms of cranial trau- ma and thrombotic pathology of the venous structures. The initial diagnostic evaluation is nevertheless left to non-invasive methods such as CT, MR and Doppler ultrasound, which are now able to satisfy the most urgent diagnostic requirements. Generally speaking, angiography is presently used in those cases in which non-invasive techniques have ex- hausted their usefulness, and, above all, when treatment using endovascular techniques is being considered.
Cerebral ischaemia
In cerebral ischaemia, depending on whether it manifests itself as TIA or frank infarction, an- giography is not routinely used except in specif- ic cases during certain time periods following the ischaemic ictus.
a) Transient ischaemic attacks: TIA’s do not usually constitute an angiographic emergency;
patients with TIA’s are typically subjected to an- giography only after a certain period of time during which the clinical evolution and the less invasive diagnostic techniques (e.g., ultrasound) have indicated the presence of a vascular lesion that might be amenable to surgery. Although in-
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CONVENTIONAL ANGIOGRAPHY
F. Florio, M. Nardella, S. Balzano, V. Strizzi, T. Scarabino
frequently encountered, angiographic examina- tions can be mandatory in patients suffering from repeated ischaemic attacks and having a non-invasive imaging diagnosis of subtotal oc- clusion of one of the cervicocranial vessels; in such cases urgent surgery or angioplasty may be able to prevent total vascular thrombosis.
b) Cerebral infarction: Angiography is rarely used today in cases of frank cerebral infarction, and is in any case usually delayed until partial functional clinical recovery is observed.
Trends recently have pointed towards utiliz- ing very early angiographic examinations, with- in hours following the acute ischaemic event, when the clinical syndrome can be attributed to an arterial occlusion that may be susceptible to treatment using transcatheter fibrinolysis. This is one of the more recent innovations of inter- ventional neuroradiology, although its real clin- ical efficacy merits further investigation (2).
Cerebral haemorrhage
Angiography plays a more important role in cases of cerebral haemorrhage.
a) Parenchymal haemorrhages do not usually require angiographic analysis when the origin of the haemorrhage is thought to be sponta- neous (i.e., elderly patient with hypertension).
However, when clinical and anatomical condi- tions favour a different aetiology for the haem- orrhage (e.g., relatively young patient, nor- motensive, atypical position, etc.), angiography becomes mandatory and should be performed urgently, especially when the haemorrhage de- mands emergency surgery.
b) In cases of epidural/subdural haemor- rages emergency angiography has varying diag- nostic importance. It is unusual for posttrau- matic epidural/subdural haemorrages to gain diagnostic benefit from angiography. Angiogra- phy can only be justified when associated le- sions of the cerebral vessels are suspected (e.g., dissection or rupture of a vessel wall, posttrau- matic aneurysms, arteriovenous malforma- tions/fistulae).
c) Angiography has a different importance in the case of subarachnoid haemorrhage. With
its often abrupt onset and typical clinical pic- ture, subarachnoid haemorrhage is the most frequently encountered of the potential neuro- logical angiographic emergencies.
Thrombosis of the cerebral veins and dural venous sinuses
This type of pathology, now somewhat rare, can require emergency angiography when in- tracranial hypertension dominates the clinical picture. In such cases, angiography is used to confirm the clinicoradiological suspicions.
However, while the cranial dural venous sinus- es are more critically assessed angiographically, digital subtraction angiography (DSA) is only capable of providing indirect information on the thrombosis of cortical venous structures (e.g., slow arterial and venous circulation, areas of paucity of venous vessels, presence of collat- eral venous circulation).
TECHNIQUES
Angiography performed in emergency con- ditions is relatively difficult and requires a cer- tain degree of experience as it is almost always performed in less than ideal circumstances.
This difficulty is due both to the patient’s state
of consciousness and ability to cooperate as
well as to the gravity of the clinical picture,
which requires the utmost rapidity of angio-
graphic examination execution and immediate
interpretation. The use of conventional angiog-
raphy has been much improved by the advent
of modern DSA appliances with high spatial
definition (1024 x 1024 matrix). DSA allows,
above all, reduced examination times, while the
marked simplification of the radiographic tech-
nique has made it possible to limit the total
amount of contrast medium required for each
individual injection. In addition, the use of low
concentration, low osmolarity, non-ionic con-
trast agents has reduced the potential contrast
agent toxicity risk. In short, DSA has evolved
into the a much simpler imaging modality with
less risk to the patient.
The only drawback of DSA is its sensitivity to even the slightest patient motion; this re- quires complete patient immobilization, which is typically only possible with deep sedation or general anaesthesia. If there are no specific con- traindications, such as underlying cerebral haemorrhage, minimal heparinization can be undertaken. With these exceptions, no other particular patient preparation is usually re- quired.
Patient vital functions and neurological sta- tus should be monitored constantly during the examination, and the patient should be kept under observation for 12-24 hours after the procedure. In the absence of contraindica- tions, the angiogram is performed through transfemoral access. Other routes of access (e.g., axillary, common carotid arteries) have a higher risk of local complications. Preliminary arch aortography used to explore the large supra-aortic arterial branches is preferable in general and specifically indispensable for iden- tifying vacular variations and ostial/proximal atherosclerotic lesions. In order to study the aortic arch and its branches, the left anterior oblique projection is used with an angulation of 15-20 degrees; generally speaking, 20-25 ml of contrast medium are required with a flow rate of 10-15 ml/sec delivered over 1-2 sec- onds (total contrast volume: 25-50 ml). Stud- ies of the carotid bifurcation require both oblique projections in order to project the in- ternal carotid free from the external carotid artery, as well as to study the walls and lumen of the vascular structures circumferentially.
Although panoramic imaging of the cranial vasculature can be useful as a preliminary ap- proach to locating major lesions and to analyse overall haemodynamic balance of flow between the cerebral hemispheres, selective catheterization of the cerebral vessels is almost always essential. Each arterial injection exam- ined requires at least the two orthogonal pro- jections during DSA; in many cases oblique projection imaging also needs to be performed in order to properly define the pathology.
Each individual injection usually requires not more than 6-9 ml of contrast medium deliv- ered at a rate of 6 ml per second (more in
cases of arteriovenous malformation or large arteriovenous fistula). In latest generation an- giographic appliances, the examination is fa- cilitated by improvements such as rotational angiography or even 3D angiography (20).
APPLICATIONS
We will examine the dual diagnostic and therapeutic role of angiography in ischaemic and haemorrhagic pathology, and omit trauma and thrombotic pathology of the venous struc- tures, which are more rarely observed at emer- gency diagnostic cerebral angiography.
Diagnostic role
In cases of ischaemia and haemorrhage, an- giography is usually principally responsible for identifying the vascular lesion(s) responsible for the clinical syndrome and for definitively determining the plan for therapy.
a) Cerebral ischaemia: Regardless of whether it involves transient ischaemic attacks or frank infarction, the principle role of DSA is simply to identify the vascular lesion(s) responsible for the ischaemia. Further goals include the analy- sis of the degree of the stenotic/occlusive pathology and an estimation of its haemody- namic significance, exclusion of the presence of other lesions that could affect treatment and provision of a complete picture of cerebral haemodynamics. Another important factor is the characterization of such lesions: whether they are atherosclerotic, dysplastic (e.g., fibro- muscular dysplasia) or related to trauma (e.g., arterial dissection); and whether there are asso- ciated complications (e.g., intraluminal throm- bus, ulceration of atherosclerotic plaques) (Fig.
1.101). In actual fact, today there are a number of examination techniques available (Echo- Colour-Doppler, MR angiography, CT angiog- raphy and SPECT), which alongside angiogra- phy contribute to this global evaluation and fi- nally to the formulation of treatment choices.
b) Cerebral Haemorrhage: In the presence
of haemorrhages, cerebral angiography plays a
Fig. 1.101 - (a-e) Cerebral ischaemia. (a-c) selective catheterism of the common carotid artery. In (a) plaque at the start of the inter- nal carotid artery, with “rose thorn” image due to ulcer (arrow); kinking in the precranial stretch (small arrows); in b) irregular plaque (ulcerated). (d-e) Ultrasound of the carotid bifurcation. In (d) marked intimal thickening with flat plaques (arrowhead); in (e) coarse sclerocalcific plaque (arrow).
a
c d e
b
more complex role. Nevertheless, in cases of in- traparenchymal haemorrhage, when performed correctly using proper techniques, angiography is able to identify or exclude the existence of associated underlying aneurysms or vascular malformations.
With AVM’s, utmost attention must be paid to determining the arterial feeders, venous drainage and other singular anatomical and haemodynamic characteristics of the malforma- tion (Fig. 1.102). This information is essential for treatment planning and for optimally choos- ing between surgery and transcatheter embolic therapy.
The recent interest in intraoperative angiog- raphy made possible by the new portable and manageable DSA appliances have allowed to conduct angiographic examinations directly on the operating table. This approach could prove invaluable in immediate preoperative, intraop- erative and postoperative evaluations of vascu- lar malformations in patients with intra- parenchymal haemorrhage.
In the presence of subarachnoid haemor- rhage the use of angiography is even more im- portant and is essential in most cases to de- termine the optimal surgical approach. An- giography is the most suitable method for di- rectly demonstrating the cause of the bleed (e.g., aneurysm or malformation) in such cas- es. At present, MR angiography and CT an- giography can identify large and many of the smaller aneurysms; however, in patients with subarachnoid haemorrhage, negative MR an- giography does not rule out the presence of an underlying aneurysm or vascular malfor- mation. Therefore, although invasive selective angiography is not completely devoid of risks, at the present time it remains the most sensi- tive angiographic technique. Selecting the time at which to perform the examination is particularly difficult, and is much dependent upon the presence or absence of arterial va- sospasm and the timing of surgery. Perform- ing angiography in the period during which vasospasm is most likely to be present (3-10 days after the bleed) can lead to a masking of the presence of the aneurysm sack due to non- filling. The decision as to whether to perform
angiography either in the early phase (day one) following subarachnoid haemorrhage or later (two weeks) depends upon the decision of the surgical team and the patient’s clinical condition. This examination requires experi- ence and diligence, paying particular attention to detail. It should also be pointed out that in certain situations, despite the utmost care in angiographic examination execution and in- terpretation, the study can be negative due to partial or total thrombotic occlusion of the aneurysmal lumen or to the persistence of the arterial vasospasm (18). Angiography permits an evaluation of the size of the aneurysm, its shape and its neck (Fig. 1.103). Angiography is also required to evaluate the entire cerebral arterial system both to search for other possi- ble aneurysms as well as to perform a com- plete presurgical haemodynamic assessment.
To this end, it can be useful to perform cross- compression of the contralateral cervical carotid artery during carotid injections in or- der to study the cross-filling, and therefore the collateral circulatory capacity, of the elements of the circle of Willis.
Therapeutic role
The interest and utility of interventional radi- ology is increasing in the neuroradiological field, especially in certain emergency situations where it can provide support for or even replacement of traditional therapeutic approaches.
Cerebral ischaemia: In cerebral ischaemia, the principal therapeutic use of angiography is selective intraarterial fibrinolysis and percuta- neous angioplasty.
a) For some years now, selective intraarter-
ial fibrinolysis has been used in treating acute
ischaemia of the lower extremities as well as
other regions of the body (e.g., renal, mesen-
teric, coronary ischaemia). This has occurred
primarily because of the introduction of new,
efficient fibrinolytic drugs that are easy to han-
dle and have low incidence of untoward side
effects. Its use in the treatment of cerebral is-
chaemia, which in industrialized countries ac-
counts for the third largest cause of death and
is the most common cause of lifetime disabil- ity, is now available in many centres world- wide.
Treatment must be begun within 6-8 hours from onset of the ischaemic ictus, once an- giography has demonstrated the obstructive nature of the ischaemia. A microcatheter is in- troduced via the transfemoral route into the occluded artery; the distal tip of the catheter is positioned in contact with the thrombus and injecting from 200,000 to 1,000,000 Urokinase; 1/3 of the total amount of the dose is administered as a bolus, and the remainder as a continuous infusion over the subsequent 1-2 hours. The main hindrance to the wider use of this technique is the extreme sensitivi- ty of the cerebral tissue to anoxia, which leaves a very small time margin between on- set and the start of treatment, and the poten- tial risk of peripheral non-cerebral and cere-
bral haemorrhagic complications (Fig. 1.104).
The procedure requires a high degree of spe- cific physician experience and a high level of organization of the medical and paramedical team involved. It is therefore typically only performed in highly specialized centres and in selected patients. However, statistics reveal encouraging figures for this technique. By re- specting rigid patient selection criteria, re- canalization of the occluded vessel varies from 44% to 100% of cases, and partial or total re- gression of the clinical picture is observed in 31% - 100% of cases (3, 7, 22).
b) Until recently, percutaneous angioplasty, has found fertile ground in areas of the body outside the brachiocephalic region. The con- tinuous technical evolution of the materials used (e.g., small calibre PTA catheters, thin- ner guide wires and flexible stents), the expe- rience gained in other body regions and the
Fig. 1.102 - (a-c) Intraparenchymal haemorrhage. a) CT: volu- minous intraparenchymal haematoma in right temporoparietal position of recent onset, with intraventricular expansion. (b-c) Selective catheterism of the right internal carotid artery, early and late arteriographic phase of same case: arteriovenous mal- formation (arrow) sustained by branches of the middle cerebral artery and the rear choroid arteries, with venous drain through ascending superficial veins (arrowheads).
a
b c
perfection of medical support have made it possible to extend PTA to the supraaortic ves- sels, albeit with application and selection cri- teria that are yet to be universally accepted. It may be that PTA is not absolutely required in hyperacute emergency situations, however, it
may be useful to perform this therapeutic pro- cedure in a timely manner subacutely in pa- tients with rapidly worsening transient is- chaemic syndromes, when preceding angiog- raphy demonstrates the presence of a severe stenosis that is felt to be responsible for the
Fig. 1.103 - (a-d) Subarachnoid haemorrhage. a) CT: subarachnoid blood expansion, at the occipital region of the cortical sulci (ar- rows). b) selective catheterism of the left vertebral artery (same case): small aneurysm of the left posterior cerebral artery, near to the start of the temporooccipital artery (arrow). c) selective catheterism of the left internal carotid artery: small sac-shaped aneurysm of the anterior communicating artery (arrow). d) selective catheterism of the left internal carotid artery: aneurysm of the anterior com- municating artery (arrowhead); spasm of the anterior cerebral artery (arrow).
a
c
b
d
clinical picture; in such cases one may logical- ly predict the vessel’s rapid evolution to com- plete occlusion and perhaps resulting frank cerebral infarction. In some specialized cen- tres, PTA of the supraaortic vascular branch- es is performed at the origins of the supraaor- tic vessels (Fig. 1.105) and within the vertebral arteries, the extracranial and sometimes even the intracranial segments of the internal carotid arteries (Fig. 1.106), and the first or- der branches of the major cerebral arteries. Al- though experience in this field is still some- what limited, it is widely held that PTA rep- resents a valid alternative to thromboen- darterectomy, at least in patients who are at high surgical risk or who present with stenoses that are difficult to access surgically; however, it may well become more widely used as more sophisticated materials and instruments are made available.
Recent statistics have shown that PTA en- ables the recovery of vascular patency in more than 90% of cases; in the remaining 10% a modest residual stenosis remains. The frequen- cy of intra- or postangiographic complications is relatively low (minor infarction: 1.6%, major infarction: 0.9%), as is the procedural death rate (0.4%) (1, 5, 6, 10-12, 19).
It should also be pointed out that emer- gency PTA can sometimes be performed on patients with subarachnoid haemorrhage caused by cerebral aneurysm rupture, where the clinical picture is dominated by the is- chaemia caused by the vasospasm. It has been found that the arterial spasm responds well to dilation. Such patients are first treated with in- traarterial papaverine (150-300 mg in 100 cm
3of physiological solution injected over 30 min- utes) using a microcatheter that is introduced into the cerebral artery as far as the vascular spasm to be treated. In cases where papaver- ine treatment is unsuccessful, PTA is used first (Fig. 1.107) (4, 13, 14, 17).
In cases of subarachnoid haemorrhage, PTA’s largest contribution to interventional radiology is in the percutaneous treatment of cerebral aneurysms using Guglielmi detachable coils (GDC). This widely used treatment is the most recent and perhaps the most fascinating and
Fig. 1.104 - (a, b) Intraarterial fibrinolysis. a) selective catheter- ism of the left vertebral artery: acute thromboembolic occlu- sion of stretch V3, with impossibility of viewing the basilar stem and the posterior circulation (arrow tips). b) check-up af- ter fibrinolytic treatment: complete recanalization of the verte- bral artery with opacification of the basilar stem and posterior circle (arrowheads)
a
b
promising interventional radiological technique in the neurological field. Through femoral arteri- al access, selective vascular catheterization into the specific vessel off of which the aneurysm orig- inates is performed; using a microcatheter to se- lectively enter the lumen of the aneurysm, GDC’s are introduced into the sack until a preferably complete occlusion is obtained. The technique’s degree of invasiveness, if compared to surgical
clipping, is far lower and the procedure is far eas- ier for patients in any condition to tolerate. How- ever, patients to be subjected to this treatment must be carefully chosen. The best results are ob- tained for small diameter aneurysms with narrow necks (90% success rate with low mortality and morbidity rates) (Fig. 1.108).
Obviously, this kind of procedure achieves the best results when practiced under ideal
Fig. 1.105 - (a-d) Angioplasty of the left subclavian artery. (a-c) Aortogra- phy in early and late stages: suboccluding stenoses at the start of the left subclavian artery (arrow); in a and b, non-opaque homolateral vertebral ar- tery; c) late opacification, against the stream of the homolateral vertebral artery (theft) (arrows). d) Check-up after angioplasty (same case): complete dilation of the stenotic tract (arrow); swift opacification of the homolateral vertebral artery (arrows).
a b c
d
conditions; however, it can still be used in emergency situations. According to Moret, of 124 cases presenting with subarachnoid haem- orrhage related to ruptured aneurysms, 21 were treated in emergency conditions (17%), with a global success rate of coil embolization of 79%
(9, 15, 16, 21).
CONCLUSIONS
In short, cerebral angiography offers a wide range of practical opportunities for use in the field of neurological emergency, and the role of this technique applied to various clinical situations is extremely varied. How- ever, it should be pointed out how the role of angiography has changed in recent years both with regard to use in emergency and routine clinical conditions, thanks mainly to the in- vention of new imaging techniques. Angio- graphic semeiotics itself has also changed, and unfortunately a portion of its refined se- meiological knowledge has gradually been forgotten. At the same time, the angiograph- ic radiologist’s role has also changed. From a certain point of view his or her task has be-
come increasingly straightforward due to the technical advances made in angiographic ap- pliances, and the sophistication of the instru- ments used have made angiographic examina- tions safer and more patient tolerable. In ad- dition, newer imaging techniques have great- ly simplified angiography’s diagnostic role.
However, from other points of view, the ra- diologist’s task has become more complex, due in part to the vast range of imaging techniques currently available. The imaging specialist’s ap- proach to any type of pathology has now be- come multidisciplinary, which makes obtaining sufficient expertise and experience with all the various diagnostic techniques and then choos- ing the optimal diagnostic-therapeutic pathway somewhat taxing.
However, the powerful development of in- terventional radiology has also made the ra- diologist’s task more delicate by requiring a thorough knowledge of both routine and emergency clinical problems, a continuous upgrading of his knowledge of appliances and instruments that are themselves under- going constant evolution, and familiarity with the use of a vast number of pharmacological preparations.
Fig. 1.106 - (a, b) Angioplasty of the internal carotid artery. Selective catheterism of the right internal carotid artery. 33 year-old pa- tient with history of cerebral ischaemia. a) Segmentary stenosis at the passage between the extra- and intracranial tract, probably of a fibrodysplasic nature (arrow). b) Check-up after angioplasty (same case): complete resolution of stenosis.
a b
Fig. 1.107 - (a, b) Angioplasty of the middle cerebral artery. a) Selective angiography of the right internal carotid artery: serrated spasm post SAH of the M1 stretch of the middle cerebral artery (arrow) in patient operated for an aneurysm on the posterior communicat- ing artery. b) Check-up after papaverine + PTA: complete resolution of the spasm with patent vessel of a good calibre (arrow tip).
Fig. 1.108 - (a, b) Aneurysm embolization with Gugliemi’s detachable coils. a) Selective angiography of the left vertebral artery: 1 cm aneurysm of the apex of the basilar artery (arrow). b) Check-up after embolization: complete occlusion of the aneurysmatic sack with well-compacted spirals (arrow tips).
a b
a b
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