Korean Journal of Cerebrovascular Surgery 2001;3(1):11-18.
Published online March 1, 2001.
Neuroendovascular Therapy-Current Technical Advancement.
Ezura, Masayuki , Takahashi, Akira , Yoshimoto, Takashi
1Department of Neuroendovascular Therapy, Kohnan Hospital, Sendai, Japan.
2Department of Neuroendovascular Therapy, Tohoku University, Scholl of Medicine, Sendai, Japan.
3Department of Neurosurgery, Tohoku University, Scholl of Medicine, Sendai, Japan.
Abstract
This article surveys current technical advancement in neuroendovascular therapy. The technical advancement happens not only in the field of products of microcatheter and guide wire but in the field of diagnosis. In the local intraarterial fibrinolysis, diffusion weighted MR imaging allows us more precise patient selection. In the atherosclerotic lesions, stent is clinically available. Some types of stent can be used in intracranial arteries. In the acutely ruptured aneurysm, intraanerysmal embolization using Guglielmi detachable coil followed by intratechal tissue-type plasminogen activator reduced occurring rate of vasospasm. In the wide neck aneurysm, neck plasty technique brings us better results. Neuroendovascular therapy is still evolving supported by such technical advancement.
Key Words: Diffusion MRI, Fibrinolysis, Guglielmi detachable coil, Neck plasty, Stent, Tissue-type plasminogen activator

Introduction


   Neuroendovascular therapy is one of treatment options, which utilizes a microcatheter introduced into an intracranial artery. There are several limitations for introduction of a catheter into intracranial arteries such as physiological tortuosity, small diameter, and so on. These limitations do not allow us to introduce complex catheters in intracranial arteries. Neuroendovascular therapy has to negotiate these limitations. Recent technical advancement, however, makes it possible to perform complicated procedure in the intracranial arteries. The technical advancement happens not only in the field of products of microcatheter and guide wire but in the field of diagnosis. In this article, authors introduce current technical advancement that allows us performing neuroendovascular therapy more precisely and more skillfully.

General Aspects

   Cerebral angiography is still essential for patients with acute stroke. Neuroendovascular therapy can immediately follow the diagnostic cerebral angiography. Thus, neuroendovascular therapy is a time-saving method in treatment of acute stroke. We ordinarily insert 6 to 8F introducing catheter into an internal carotid artery or a vertebral artery. Invasion of this therapy to a body is thought to be similar to that of cerebral angiography. It can performed under local anesthesia. General anesthesia is sometimes required in the case in which slight movement of the patient may greatly influence treatment result. The depth and duration of the general anesthesia are minimal even in such case. Systemic heparinazation is necessary in most cases because of complicated procedure on the way to cerebral parenchyma.

Local Intraarterial Fibrionlysis for Acute Embolic MCA Occlusion

   Local intraarterial fibrionlysis (LIF) can be indicated for embolic occlusion in every cerebral major trunk. Among them, middle cerebral artery (MCA) is most favorable for LIF. Basilar artery occlusion is difficult to evaluate cerebral blood flow (CBF) because single photon emission CT (SPECT) is not so useful in posterior fossa. Reduction of CBF is too severe in internal carotid artery (ICA) occlusion to perform LIF safely. So, we will focus on LIF for acute embolic MCA occlusion.
   Indication criteria of LIF for MCA occlusion are 1) less than 75-year-old, 2) within 6 hours from onset, 3) no responsible findings on CT, 4) residual flow is 35-70% comparing unaffected side, if single photon emission CT (SPECT) is available.4)5) Table 1 shows an algorithm for acute ischemic patient in our hospital. We performed LIF using tissue-type plasminogen activator (tPA) in 77 patients with MCA occlusion in last 13 years. There were 54 males and 23 females with an average age of 63.5 years. Recanalization is achieved in 73 cases (95%). Complete recanalization is in 27 cases (35.1%) and half recanalization (100-50% of its territory) in 38 cases (49.4%). Interval between onset and admission, start of angiography, recanalization was 2.4 hours, 3.5 hours, and 5.5 hours, respectively. National Institute of Health Stroke Scale improved in 51 cases (63.6%) in next day. Modified Rankin Scale is 3 or better in 44 cases (57.1%) at 1 month later. There was no complication related to the procedure.
   Fibrinolytic therapy for the treatment of patients with acute ischemic event has been the center of much controversy as to its effectiveness and safety, in particular the selection of intraarterial or intravenous injection, the fibrinolytic agent, and the necessary dose of the agent. Although several multicenter trials of intravenous fibrinolytic therapy failed to find any benefit,3)9)11)17) the most recent investigation has finally proved both the effectiveness and safety of intravenous recombinant tPA administration.18) Intraarterial fibrinolysis has been used in too feww cases to compare with intravenous administration. Recently, however, the Prolyse in Acute Cerebral Thromboembolism trial has proved both the effectiveness and safety of intraarterial infusion of recombinant pro-urokinase.1) On the basis of our own experiences discribed above, recanalization is achieved more often and more rapidly by intraarterial than intravenous administration. Therefore, we think that intraarterial fibrinolysis is the method of choice despite the potential risk.
   In this series, 9 patients underwent not only SPECT but diffusion weighted (DW) MR imaging followed by LIF. Recanalization was observed in all 9 patients7) (Fig. 1). Eight patients improved clinically. The high signal intensity area on preoperative DW MR imaging was smaller than the low uptake area on SPECT in all patients. The high signal intensity area on preoperative DW MR imaging developed cerebral infarction detected by postoperative MR imaging or computed tomography 3 days after onset in all patients (Fig. 2). We conclude that the high signal intensity area on DW MR imaging correlates, at least clinically, with irreversible brain damage. Therefore, acute local fibrinolysis should not be performed in patients with high signal intensity areas in the cortex responsible for the symptoms. SPECT remains important, because normal areas on DW MR imaging with low uptake on SPECT often contribute to the functional prognosis.

Stent for Atherosclerotic Lesions

   Stenting for cerebro-cervical region was performed in 24 patients (M:21, F:3, ave. 64.5 y.o.) of 25 sessions between June 1995 and March 2000.2)12)13) Lesions were ICA stenosis at its origin in 13 patients, ICA at petrous portion in 2, ICA dissection in 3,14) common carotid artery stenosis in 1, vertebral artery (VA) stenosis in 3, subclavian artery (SCA) stenosis in 1, and SCA occlusion in 1. Three patients with ICA stenosis were treated in the acute stage.10) Three sessions (ICA stenosis, VA stenosis, SCA occlusion) were retreatment following failed PTA. In early in our series, we used balloon-expandable stent because it was only stent clinically available. Recently, we use self-expandable stent for ICA at its origin (Fig. 3). Balloon-expandable stent is still used for smaller vessel such as intracranial ICA or larger vessel such as SCA. Initial success was obtained in all patients except one acutely treated case. All complications observed were transient bradycardia requiring intravenous pacing in 3 patients. Restenosis was observed in 5 patients out of 13 in whom follow-up angiography was available. All of them were treated with balloon-expandable stent. In our early experiences, stenting for cerebro-cervical region is safe and effective, especially using self-expandable stent.

GDC Embolization for Acutely Ruptured AN

   In this chapter, we will focus on our treatment protocol and results on the intraaneurysmal Guglielmi detachable coil (GDC) embolization for ruptured aneurysm in the acute stage.
   This study consists of 39 patients who were treated with intraaneurysmal embolization within 72 hours after the onset of subarachnoid hemorrhage from March 1997, when our technique of GDC embolization was stabilized, to May 1999. Patients who were initially treated by craniotomy were excluded. Patients with cerebral aneurysms were always considered to be a possible candidate for neurosurgical clipping. If the patient had any difficulties and/or problems on neurosurgical clipping, the patient was treated by intraaneurysmal GDC embolization. Neck plasty technique was not performed in the acute stage but in the chronic stage. Patients' age ranged form 42 to 86 years (av. 73.2). There were 8 males and 31 females. The Hunt and Kosnik (H & K) grade was I in 1, II in 19, III in 9, IV in 7, and V in 3.
   The embolization was performed under general anesthesia in all cases. Anticoagulation method was initially systemic low molecular weight heparinization only during procedure till Aprill 1998, then systemic heparinization after deployment of first coil and only during procedure. Double marker microcatheter was introduced into the aneurysm through a 6F introducing catheter. GDCs were inserted as tightly as possible compromising with thromboembolic complication (Fig. 4). Then, spinal drainage was set in patients with thick subarachnoid hemorrhage (Fisher Group II, III) and tPA was administered via the drainage6) in patients with thicker subarachnoid hemorrhage (Fisher Group III). Then, tPA was administered once a day by bolus injection of 2 mg until most subarachnoid clot disappeared in computed tomographic scan finding (Fig. 5).
   The reasons for GDC embolization were high age in 24 patients, poor grade in 12, surgically difficult location in 11, systemic disease in 2, and others in 3 (Table 2). The location of the aneurysms was on ICA in 16, MCA 3, anterior communicating artery (AcomA) 6, anterior cerebral artery (ACA) 2, VA 3, basilar artery 8, and posterior cerebral artery 1 (Table 3).
   Spinal drainage was set in 22 patients and tPA was administered in 12 patients. Symptomatic vasospasm was observed in 2 patients (5.1%). Both patients were treated by spinal drainage alone.
   Angiographic result immediately after embolization was complete obliteration (CO) in 9, neck remnant (NR) in 20, and body filling (BF) in 10. Two patients experienced rerupture during peritherapeutic period. Angiographic result at 6 months' follow-up was CO in 3, NR in 11, and BF in 5. Repeated embolization was carried out in 2 of 11 patients with NR and 1 of 5 patients with FB.
   Table 4 shows relationship between H & K grade immediately before embolization and Glasgow outcome scale at discharge. In 29 patients with H & K grade I, II or III, 25 (86%) were good recovery (GR) or moderate disability (MD). Even in 7 patients with H & K grade IV, 5 (71%) were GR or MD.
   Complications were divided into 3 ranks depending on clinical symptom£ºmajor, minor, and asymptomatic. Distal embolism occurred in 4 patients. One patient died of distal embolism (major complication) and the other 3 patients with distal embolism were asymptomatic. Three patients showed parent artery occlusion with major symptom. One of them died of the parent artery occlusion. So, there are 2 mortality derived from complcation. Both patients were originally H & K grade II.
   If we compared recent patients treated by embolization with initial ones, there were several differences between them. Those patients who were treated by embolization because of their poor clinical grade decreased in recent series. We expected favorable effects of embolization for poor grade patients when we started GDC embolization for acutely ruptured aneurysm. However, the favorable effects were minimal, though they surely existed. Recently, we consider H & K grade V as contraindication. In the relation of limited poor grade patients, mortality decreased in recent series.
   There were no patients who were treated under local anesthesia in recent series. The principal reason is one excellent neuroanestheologist has had a post in our hospital.
   Concerning aneurysm location, ICA aneurysms increased and AcomA aneurysms decreased. That briefly demonstrates ICA aneurysms are suitable for embolization and AcomA aneurysms are not.
   We concluded that low molecular weight heparin is not reliable, so we started using regular heparin. The major problem on low molecular weight heparin is not in the drug itself but in monitoring method. There is no reliable monitoring method for low molecular weight heparin. Activated clotting time combined with Xa factor is not very stable.
   Our protocol of GDC embolization for ruptured aneurysm in the acute stage is as follows:1) General anesthesia, 2) without neck plasty, 3) H & K grade V is contraindecated, 4) regular heparin only during procedure, 5) spinal drainage, if necessary, with or without tPA.
   If we follow the protocol above, 80% of all patients and 86% of patients with H & K grades I to III show good outcome, Complete obliteration is achieved in 30% of the patients. Neck remnant is in 50% of the patients and patients with neck remnant may suffer from rebleeding. Symptomatic vasospasm occurs in 5%. The problems on the GDC embolization for ruptured aneurysm in the acute stage are:
   1) Only complete obliteration guarantees relief from rebleeding.8)
   2) Stable embolization is not always performed and retreatment is required in 8% of the patients.
   In conclusions, at present, intraaneurysmal GDC embolization is indicated in the patients in whom surgical clipping is not indicated for the reasons such as high age, poor grade, surgically difficult location, etc.

GDC Embolization for Wide Neck AN

   Neck plasty technique is one of solution for embolization for wide neck aneurysm. This technique characterized by a balloon microcatheter introduced across the neck of the aneurysm15) (Fig. 6). The procedure itself is more complicated than simple catheterization technique. Moreover, wide neck aneurysm theoreticall has wide surface of the naked coils facing to blood flow. Therefore, we consider systemic heparinization is essential for this technique. This is why we never utilize this technique for acutely ruptured cases.
   We utilized this technique for 56 wide neck aneurysms between April 1995 and March 2000. The definition of the wide neck is;body/neck ratio does not exceed 2 or the absolute neck width is more than 4 mm. Table 5 shows location of the aneurysm and number of the cases. We can utilize this technique in distal artery territory such as ACA and MCA. In the case of basilar tip aneurysm, we sometimes used two balloons.16) Systemic heparinization was performed during and up to 48 hours after embolization. Embolization results are CO in 30, NR in 19, and BF in 7, at 1 week after the embolization and CO in 30, NR in 10, and BF in 4 at last follow-up. These results are seemed to be very good considering background of wide neck. Most frequent complication is parent artery occlusion that affects patient's life partially in 6 patients. Hemorrhargic tendency due to tight heparinization cause preshock that require transfusion in 3 patients.
   Neck plastic intraaneurysmal GDC embolization by means of parent arterial balloon protective has following advatages. The first point is the prevention of the coil protrusion into the parent artery, though this is also possible by intraaneurysmal balloon protection. The second point is that neck plasty makes it possible to perform reconstructive embolization. The patent lumen of the parent artery would be conformed as the original arterial lumen. The third point is to facilitate more compact packing by fixing the position of a microcatheter while introducing GDC. During inflation of the protective balloon, the microcatheter is fixed in the position. This fixation of the catheter tip makes stable and compack embolization possible. Stable and compack embolization would result in prevention of coil compaction.


REFERENCES


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