Transarterial Embolisation of Cerebral Arteriovenous Malformations

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1 Transarterial Embolisation of Cerebral Arteriovenous Malformations How Few Can You Do? G. WIKHOLM, C. LUNDQVIST*, P. SVENDSEN Section of Interventional Neuroradiology, Department of Radiology, * Department of Neurology, Sahlgrenska University Hospital; GOteborg Key words: arteriovenous malformation, cerebral, brain, embolisation, complication, outcome, result Summary Arteriovenous malformations of the brain are rare disorders. Embolisation has emerged as an effective treatment with an acceptable, low complication rate. Previously presented results are completed with results from 1994 to Ninety-six percent of the patients were treated with no or very minor sequelae resulting in total obliteration in 32% and supplementary stereotactic radiation in 49%. Ninety percent of all patients are in excellent or good health at follow up. These results may be jeopardised by the ongoing proliferation of endovascular treatment for AVMs. Introduction Arteriovenous malformations of the brain (AVMs) are rare disorders with a natural history indicating a rather severe prognosis with a yearly risk for severe disability or death of about 2.5% 1,2. The incidence can be estimated to about 0.5 to 1 per 100,000 inhabitants a year u. To be able to attain and keep a level of skill giving acceptable treatment results regarding both morphological and clinical outcome, a large catchment population is necessary. This paper presents the development of our treatment results and these results are used as a background for a discussion against the ongoing proliferation to more centres for transarterial embolisation of AVMs. Material and Method Patients referred to our institution for transarterial embolisation of AVMs from 1987 up to and including 1996, if embolisation was concluded, are included in the analysis. Results from 1987 to 1993 were presented earlier as a whole group4.6. These results have further been divided into subgroups, group I ( ) and group II ( ) for comparison of evolution of treatment results 7. These two latter subgroups only included patients that entered and were through embolisation treatment during each two year interval studied. In the present study patients embolised for the first time during 1994 to 1996 (group Ill) that were through embolisation at the end of 1996 are compared with patients embolised 1987 to 1988 and 1992 to 1993 respectively. All patients embolised during the respective interval are included. The embolisation technique utilised exclusively N-butyl-cyano-acrylate (Histacryl Blue, Braun, Melsungen, Germany) as an embolic material and in almost all cases we used flowguided micro catheters (Magic, BaIt, Montmorency, France). Recently we have occasionally used thin guidewires in the catheters to fa- 119

2 Transarterial Embolisation of Cerebral Arteriovenous Malformations G. Wilkholm oo~ ~========~ -+- N. of Patients N. of Sessions O+---~~ r--~--+-~--~--~ Figure 1 Number of new patients entering the treatment programme each year and the number of treatment sessions (angiographies not included) performed during that year. cilitate insertion. The technique of embolisation is described in a previous paper4. The aim of the treatment is total obliteration of the AVM by embolisation alone and if not possible complementary stereotactic radiation has been proposed and in most instances performed. A few patients underwent surgery after embolisation. Clinical data for patients treated 1987 to 1993 were obtained through an extensive follow-up including a clinical examination of all patients alive by an independent neurologist. For patients treated 1994 to 1996 the information is new and the clinical information was collected from files from the department of neurology. The parameters accounted for here are treatment protocol, complications and clinical out- Table 1 Final treatment/morphological results in three treatment groups in percent (number in parenthesis) Total occlusion by embolisation 11 (3) 20 (7) 32 (13) Embolisation + radiation 19 (5) 49 (17) 49 (20) Embolisation + surgery 19 (5) 11 (4) 5 (2) Partial treatment* 51 (14) 20 (7) 14 (6) * Partial treatment indicates patients with remaining AMVs not suitable for further embolisation, surgery or radiation. come. The treatment protocol prescribes embolisation as long as a possibility exists to go further with acceptable risk. If the AVM is not totally obliterated by embolisation, stereotactic radiation is requested (outside institution) and if the patient is accepted this is regarded as an end point. In a few cases surgery was prescribed as supplementary treatment. In all these instances a treatment aiming at total obliteration was instituted and this is termed full treatment. In other cases with active AVM not possible to further embolise, irradiate or excise with reasonable risk, partial treatment was obtained. The level of complication was estimated about three weeks after treatment to conform with the conception "reversible ischaemic neurological deficit" (RIND). A slight complication means a negligible influence on functional status, a moderate complication means a deteriorated functional status but usually no influence on lifestyle, whereas a severe complication has an influence on quality and conduct of life. For the two first groups the clinical outcome was judged after a thorough clinical examination of all patients during 1992 to 1994, while outcome for patients in group 3 was judged from files. To describe the outcome, we used the following scale, slightly modified after Heros et A18: Excellent = Patient returned to previous lifestyle. Good = Patient returned to previous lifestyle but with a minor deficit. Fair = Due to a new deficit, patient could not return to previous lifestyle but could lead an independent life. Poor = Due to a new deficit, patient is dependent on others for daily living. Death from embolisation = Death at or within four weeks after the treatment session. Death from AVM event = Death directly related to AVM more than four weeks after the treatment session. Death from other cause = Non-AVM related death. Results A total of 211 patients were treated from 1987 to The yearly inflow of patients and the yearly number of embolisation sessions is 120

3 presented in figure 1. As stated above a complete account of the outcome of the patients 30 treated 1987 to 1993 was published earlier ~ The results presented here are the most important key figures to be utilised in an evaluation 20 of the continuing development. 15 The mean volume of the AVMs was der 0 I '. creased between group I and 11 from 27 to r '. (. j>; cc. If four very large AVMs (volume 110 to ,:,: cc) are excluded from the first group the mean 0 volume in that group decreased to 22 cc. The mean volume in group III was 15 ml (figure 2). The results regarding final treatment and morphology are listed in table 1. A substantial increase in the frequency of total obliteration Figure 2 Mean volume of AVMs treated during the diffrom embolisation alone was obtained as well ferent time periods. In the bar for 1987 to 1988 a horizontal line indicates the effect on the mean size of AVMs treated as a decrease in the frequency of partial treat- that year if four very large AVMs are excluded. ment. The level of complications in the different groups is presented in table 2. A slight further improvement has been obtained. During the last three years 96% of the patients have gone through embolisation with no or very minor Level of complication 0/0 N. 0/0 N. 0/0 N. complication. The one severe complication occurred in a patient with an AVM supplied by a No 48 (13) 78 (27) 81 (33) superior cerebellar artery. H ';... '-2:: Table 2 The level of complications during the different time periods in percent (numbers in parenthesis) A functional cerebellar branch was occluded Slight 26 (7) 11 (4) 15 (6) by glue at the same time as the AVM was totally Moderate 15 (4) 11 (4) 2 (1) occluded. The patient did well for two days but Severe 11 (3) o (0) 2 (1) after that deteriorated with MRI showing brainstem and bilateral cerebellar ischaemia. Death o (0) o (0) o (0) No venous overflow was observed (the emboli- sation procedure is recorded on videotape and ~./ reviewed). Retrograde thrombosis may be a possibility. The patient with a moderate complication Table 3 Final outcome for patients treated during the respective time period in percent (numbers in parenthesis) had a deep AVM that had given severe deficits after haemorrhage. In an effort to reach a final angulated perforator a perforation with a guide Level of complication 0/0 N. 0/0 N. 0/0 N. wire occurred with subsequent haemorrhage with an initial deterioration. Months later the Excellent 40 (11) 82 (29) 85 (35) patient improved greatly and is now far better Good 15 (4) 6 (2) 5 (2) than immediately before embolisation. Outcome after fulfilled treatment is pre- Fair 22 (6) 9 (3) o (0) sented in table 3. Thus 90 % of the patients are Poor 4 (1) 3 (1) 5 (2) in good shape without handicaping deficits. The two patients with poor outcomes are the Death from embolisation o (0) o (0) o (0) one with a severe complication at embolisa- Death from tion and the other had a severe complication AVM haemorrhage 19 (5) o (0) 2.5 (1) at surgery. The patient who died from haemorrhage was Death from other causes o (0) o (0) 2.5 (1) under treatment and had been embolised two months earlier. The patient who died from an-./ 121

4 Transarterial Embolisation of Cerebral Arteriovenous Malformations G. Wilkholm other cause committed suicide despite successful embolisations with improvement of epilepsy. Discussion AVMs are rare disorders being diagnosed in 0.5 to 1 per 100,000 inhabitants per year 1,3. The initial event is a subarachnoid haemorrhage, an epileptic seizure or occasionally a neurological deficit or headache. Other more rare symptoms revealing the diagnosis may occur 1,3,4. Age at presentation is mostly in the third to forth decade. The natural history as described by several authors includes a cumulative risk of death or a severely handicaping deficit, not only from haemorrhage, of about 2.5% per year 1,2. This is worse than what is generally regarded as the risk for an incidentally discovered, so-called cold, pial aneurysm which carries a yearly risk of less than one percent for the same type of disability. Another interesting piece of information regarding AVMs is that even without haemorrhage they detract about two decades of life time from the patient 1. With the estimated low incidence of AVMs 45 to 90 should be diagnosed per year in Sweden with 9 million inhabitants. Some of these AVMs are treated surgically, the surgery at times prompted by large haematomas, others are treated by stereotactic radiation as the first modality. At the most 25 to 50 AVMs may remain for endovascular treatment. As shown in figure 1, our institution, being the only centre for endovascular treatment, has had a number of patients in the lower range rather constantly over the period studied. The small decrease can be explained by the fact that during 1987 to 1991 we treated a few patients from Denmark, Norway and Finland, all these countries now have their own neurointerventional services, Finland even four sites. The decrease in treatment sessions per patient probably depends on acquired experience and a slight decrease in size of referred AVMs. We have despite the diminished training due to fewer sessions succeeded in constantly improving the morphological and clinical outcome with an ongoing decrease in the frequency and severity of complications. Our results thus differ from those obtained by Frizzel and Fisher in their meta-analysis with no improvement in treatment outcome over time 9. Regarding every human activity it is necessary to practise to gain and keep competence and expertise. This is as valid for piano players, down-hill skiers and airplane pilots as for interventional neuroradiologists. In Sweden this has a general acceptance regarding for instance carotid angiography that today is performed virtually exclusively in university hospitals which are the highest referral level. If not performed on a regular basis safety and quality are jeopardised. The trend now in interventional neuroradiology is that all Swedish university hospitals (six) are in the process of starting to perform interventional procedures in the head. Aneurysm treatment is a fair reason for this movement, aneurysm being about ten times as common as AVMs. Regarding AVMs, this trend is probably universal although in Denmark an agreement has been reached to concentrate all AVM embolisations to one site. If AVM treatment were diluted to six locations in Sweden every site would have about five patients a year to embolise. Furthermore, there are no synergistic effects since the technique for AVM treatment is particular and no training is gained from treating other diseases. Another most important question has emerged during the study of the literature regarding the treatment of cerebral AVMs with embolisation. What has happened to the thousands of AVM patients already being treated with flow guided catheters and glue? Several thousand Magic catheters have been sold every month for years and is not possible to use them for anything but glue embolisation of brain AVMs. A few may be used for chemotherapy of brain tumours but according to what is reported in meetings and the literature this is a rare procedure. Frizzel and Fisher found 1246 embolised patients in their meta-analysis, several of these patients may also have appeared in different papers 9. This is obviously only a small fraction of all treated patients. Occasionally the argument that anyone involved in interventional neuroradiology must master all techniques is heard. This is not valid 122

5 in any other highly specialised care. Some neurosurgeons specialise in vascular neurosurgery, others in skull-base surgery and so on. When initiating clinical studies it is always necessary to obtain approval from ethical committees. Should there not be an approval not to initiate a follow-up study when performing treatment that is not validated regarding its efficacy? Furthermore, studies should be regarded as mandatory in all institutions in order to evaluate and maintain quality. It is not possible to refer to results from the literature and claim that these results are universal. Conclusion It has been possible to maintain and improve treatment results in an institution with a long experience regarding AVM embolisation with as few as 40 embolisation procedures by two operators a year. The ongoing proliferation of centres for this kind of treatment carries a great risk for loss of competence by decreasing the number of procedures performed by each individual. The loss of competence also afflicts the whole chain of care during the hospital stay. This obvious risk must be counterbalanced by an obvious gain. It is not easy to see what advantages this development brings to the patient. References 1 Ondra SL, Troupp H et AI: The natural history of symptomatic arteriovenous malformations of the brain: a 24- year follow-up assessment. J Neurosurg 73: , Brown Jr RD, Wiebers DO et AI: The natural history of unruptured intracranial arteriovenous malformations. J Neurosurg 68: , Crawford PM, West CR et AI: Arteriovenous malformations of the brain: natural history in unoperated patients. J Neurol Neurosurg Psychiatry 49: 1-10, Wikholm G, Lundqvist C et AI: Embolisation of cerebral arteriovenous malformations: Part I - Technique, morphology and complications. Neurosurgery 39: Lundqvist C, Wikholm G et AI: Embolisation of cerebral arteriovenous malformations: Part II - Aspects of complications and late outcome. Neurosurgery 39: Wikholm G: Role of transarterial embolisation in the management of cerebral arteriovenous malformations (Thesis). Acta Radiologica 37: Suppl 404: 1-25, Wikholm G, Lundqvist C et AI: Transarterial embolisation of cerebral arteriovenous malformations: Improvement of treatment results with experience. Am J Neuroradiol 16: , Heros RC, Korosue K et AI: Surgical excision of cerebral arteriovenous malformations: late results. Neurosurgery 26: , Frizzel RT, Fisher WS3: Cure, morbidity and mortality associated with embolisation of brain arterioveonous malformations: a review of 1246 patients in 32 series over a 35-year period. Neurosurgery 37: , Gunnar Wikholm, MD. Ph.D. Emboliseringsenheten - Rontgen Sahlgrenska University Hospital PO Box S Goteborg 123