Recursos laborales

9.1 Introduction

The findings of the investigations included in this thesis suggest that EVC is a suitable first line treatment for MCA aneurysms; that the injury sustained by brain regions heavily involved with cognition is significantly greater in patients with ACOM aneurysms treated with clipping; that clinical outcomes in patients with more severe physiological derangement are superior for coiled patients; that invasive imaging may be unnecessary in patients with PMSAH; that aggressive endovascular treatment of vasospasm results in low rates of cerebral infarction and may negate its clinical impact; and finally that long term follow-up of adequately occluded coiled aneurysms is probably not necessary.

9.2 Treatment of middle cerebral and anterior communicating artery aneurysms

Many critics of the ISAT study (Molyneux et al, 2002) state that a large proportion of the ruptured aneurysms encountered in routine practice are not characteristic of those included in the study in which equipoise for clipping or coiling was required. Although the BRAT study (McDougall et al, 2012), was designed to answer whether either modality was superior for all-comers the study design has been heavily criticised so this remains an area of controversy.

The findings of this large case series of endovascularly treated MCA aneurysms suggest that the clinical results, anatomical occlusion rates and complication rates are similar to those for aneurysms at other locations. Furthermore, results are comparable to those published for the best surgical series and the endovascular results are reproducible. There will remain some doubt, however, from proponents of surgery and since surgery in many institutions is reserved for more anatomically challenging lesions, a trial of surgery versus endovascular treatment using adjunctive endovascular treatments may well be of use to the neurovascular team. Balloon-assistance allows treatment of almost all ruptured cerebral aneurysms and current evidence suggests this can be achieved

without a significant increased risk to the patient (Pierot et al, 2012b). Balloon-

assistance was used in a handful of cases in the present series and very few of the ISAT cohort so a trial of balloon-assisted coiling versus surgery for more complex lesions is feasible. Complex unruptured lesions can now be treated with stent- assistance, flow diversion and the recent development of intra-aneurysmal flow

diverters. An additional study that would therefore be useful is a trial of surgery versus newer flow-diverting techniques.

The results of the present radiological observational study addressing rates of ischaemic injury following clipping or coiling of ACOM artery aneurysms demonstrated a marked predisposition to basal forebrain and septal/subcallosal region injury in the clipped patients. These areas are heavily involved in cognition and it is likely that this injury is responsible for inferior cognitive outcomes following surgery. Again, it could be argued by proponents of surgery that the more anatomically challenging lesions may require clipping for treatment but as the neurointerventionalist’s armamentarium increases, a trial of flow diversion/stent- assisted coiling versus surgery would be fascinating.

To improve the application of endovascular techniques in the context of subarachnoid haemorrhage, there is a need for development of stent devices that do not necessitate the use of dual anti-platelet therapy.

9.3 Aneurysm treatment modality and physiological status

The ISAT cohort was mostly of good clinical grade but we have no information on the physiological status of the patients. The results of the present work suggest that there is a relationship between treatment modality, physiological status and outcome. Clipping results in worse clinical outcomes in physiologically sicker patients. Other work has suggested that clipping is associated with higher

rates of medical and perioperative complications (Vergouwen et al, 2011c; Ayling et

al, 2015). Physiological information should probably be included in the data

collection of trials designed to answer whether surgical or endovascular options are superior for different groups of patients that were less well represented in the ISAT trial including those with more complex aneurysms requiring adjunctive endovascular options including stents and intra-aneurysmal flow diverters or patients of poorer clinical grade.

9.4 Invasive imaging in patients with perimesencephalic haemorrhage

The results of the present work suggest that DSA may not be required for investigation of perimesencephalic haemorrhage. CT angiography may be a suitable definitive investigation. Although other authors have reached similar conclusions, the validity of this investigation algorithm needs to be confirmed with higher level of evidence. A prospective study is probably required to achieve more universal acceptance. The author is presently undertaking a prospective study investigating the clinical course in patients with perimesencephalic haemorrhage investigated with CT angiography alone read by two experienced neuroradiologists.

9.5 Treatment of cerebral vasospasm using endovascular techniques

The use of endovascular techniques to treat cerebral vasospasm and the role of cerebral vasospasm in delayed ischaemia remains controversial. International guidelines state that it is reasonable to consider endovascular options in cases where

medical therapy has failed (Bederson et al, 2009). The approach in the present

studies was slightly different: endovascular treatment was started early in patients exhibiting significant angiographic vasospasm so as to prevent clinical deterioration. The adoption of this protocol will be limited in many health systems including that in the United Kingdom due to resource implications. What would be more pertinent would be to address the efficacy of endovascular treatment options in situations in which maximal medical therapy has failed to show clinical improvement. Many neurointerventionalists are reluctant to undertake balloon angioplasty for the risk of vessel rupture and in view of this, the use of intra-arterial vasodilators would seem a useful treatment option with relatively low risk. A multicentre trial comparing various intra-arterial vasodilators is in process (Chen, 2015). However, there is much work to be done on a basic science level. For example, what is the dose-response for the various agents that are commonly in clinical use? Furthermore, what is the effect of these agents on the other dominant mechanism of delayed ischaemia, spreading cortical depression? The author is in the process of designing a study using electro- encephalography to assess these interactions and also the interaction between both angiographic vasospasm and spreading cortical depression in order to fully elucidate the pathophysiology of this disease.

9.6 The necessity of long term follow-up of coiled cerebral aneurysms

The present work also suggests that long term imaging follow up beyond 6 months may not be necessary in patients with well coil-occluded cerebral aneurysms. However, this evidence was single-centre and of a retrospective nature. For this notion to gain acceptance, the level of evidence needs to be greater. This would necessitate a multicentre, prospective study in which anatomical outcomes are independently assessed with long term follow-up beyond that of 2.5 years used in the present work.