Preface

Moyamoya disease is a progressive steno-occlusive process of the terminal internal carotid artery and its main branches with the development of an extensive network of collateral vessels, mainly at the lenticulostriate and choroidal arteries [1, 2]. This condition leads to ischemic and haemorrhagic strokes [3] and cognitive decline. Disease progression is the rule if left untreated [4].

Although it is more prevalent in East Asian countries [5, 6], it is commonly diagnosed in the USA [3] and Europe [7]. A chapter will deal with the differences in the regional prevalence of moyamoya disease. Moreover, its reported prevalence has been increasing over the years partly because of higher awareness in the medical profession, better diagnostic capacities [8, 9] and regular medical brain check-ups [4, 10]. As a result, the amount of asymptomatic patients diagnosed has rosed over time [11, 12]. The question is what to do with them because being asymptomatic today does not guarantee that they will remain so forever, nor will they have no silent brain infarctions or microbleeds [13].

Moreover, in this book, we will present evidence that these patients are not entirely asymptomatic. Instead, they suffer from a steadily progressing cognitive decline [14], particularly children [15–17]. Interestingly this cognitive decay seems to precede the onset of clinical symptoms due to haemorrhagic or ischemic strokes [14].

Surgical revascularization on asymptomatic moyamoya patients is controversial, particularly in children [18]. Although medical treatment with antithrombotic drugs is used for mild asymptomatic cases, their effectiveness is limited [5, 19]. A chapter in this book will enlighten on how to get the best of the moyamoya pharmacological treatment.

Direct, indirect or combined brain revascularization have shown better long-term results than conservative treatment [18, 20, 21], and a book chapter is devoted entirely to it.

Perioperative management must be exquisite to minimize morbidity and mortality. A chapter is presented by experienced colleagues that will enlighten the way we all must follow.

This book focuses on a disease uncommon in most world areas, stressing that perhaps it is not so uncommon because there are many, perhaps too many, asymptomatic or undiagnosed cases. And yet, we need to sharpen our clinical skills to

diagnose the disease as early as possible and apply all the treatment options in due time and form. After all, this unforgiving condition will make patients pay a severe toll on sequelae and lost quality of life.

> **Vicente Vanaclocha** Professor, Department of Surgery, Division of Neurosurgery, University of Valencia, Valencia, Spain
