Endovascular Neurosurgery Through Clinical Cases

By Aristotelis P. Mitsos

Endovascular neurosurgery is a recently introduced but rapidly evolving medical field, which uses minimally invasive interventions to treat major life-threatening vascular lesions of the Central Nervous System. Although its history counts less than 15 years of worldwide acceptance, it has rapidly displaced the traditional open neurosurgical techniques, being nowadays the first treatment choice for brain aneurysms and vascular malformations. Thus, the experience of each neuroendovascular center and performer is invaluable, offering the base for learning and teaching the new generation of interventionalists as well as for the evolvement of the method itself.

This book presents the basic principles of endovascular neurosurgery starting from clinical cases. Through this close-to-clinical-reality-process, the reader will be able to more thoroughly understand the pathophysiology of the brain and spine vascular lesions as well as the decision-making strategy, related to the indications, endovascular methods and results, finding suggestions and solutions to his/her clinical questions and problems. Besides chapters devoted to CNS vascular embryology and anatomy, clinical cases organized in groups based on the treated lesions are introduced: ruptured and unruptured cerebral aneurysms of the anterior and posterior circulation, side-wall and bifurcation aneurysms, arteriovenous malformations (AVM), dural arteriovenous fistulae (dAVF), arterial stenosis and angioplasty as well as spinal vascular lesions. A separate chapter is devoted to the organization and necessary equipment of the angio room and the department offering neuroendovascular service.

This volume will be of interest to neurosurgeons, interventional neuroradiologists, vascular surgeons, neurologists and ICU physicians as well as health care providers who are involved in the diagnosis and management of the vascular lesions of the brain and spine.

• Language: English
• Publisher: Springer
• Release date: Nov 26, 2014
• ISBN: 9788847056879

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Aristotelis P. Mitsos

Endovascular Neurosurgery Through Clinical Cases

A313844_1_En_BookFrontmatter_Figa_HTML.png

Aristotelis P. Mitsos

Neuroendovascular Department, 401 General Army Hospital, Athens, Greece

ISBN 978-88-470-5686-2e-ISBN 978-88-470-5687-9

DOI 10.1007/978-88-470-5687-9

Springer Milan Heidelberg New York Dordrecht London

Library of Congress Control Number: 2014952198

© Springer-Verlag Italia 2015

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Foreword

Case reports have been dropped by many medical journals because of their negative effect on the all-important impact factor. This sad reality is due to the short time period during which an article’s citation counts towards an impact factor score. Interesting cases are generally reported because they illustrate rare conditions or features with relevance far longer than papers describing the latest tools or techniques. In time they may be cited as often or more often than such papers but outside the accounted 2 years after publication, used for comparative journal statistics.

This book proves the value of case reports for the trainee and for the interested senior. I am very proud to have been asked to write a short foreword by my former student. Aristotelis Mitsos completed a master’s degree in Interventional Neuroradiology at Oxford in 2006. One of the elements examined for the award of the degree is a logbook detailing cases the student saw during their year of study. He has developed this process, and the thought and care used to collect and document the cases in this book testifies to his diligence.

The cases give readers an opportunity to sample another doctor’s practice and provide a focus for reflection on their own. Each case highlights the challenges we face in the hospital every day. They are presented in a succinct manner and feature the details important in endovascular neurosurgery. Thank you Aristotelis for taking the time to document your experience and to share it so honestly.

James V. Byrne

Oxford, UK

Preface

Endovascular Neurosurgery or Interventional Neuroradiology are two different terms describing the same therapeutic practice in the field of vascular lesions of the central nervous system (CNS) i.e. the brain and the spinal cord. It is true that vascular lesions of the CNS, although of benign nature, may have serious or even catastrophic results for the human brain, especially if they are not treated properly in the acute or subacute phases of their clinical presentation. The ability to reach and treating these lesions using the normal endovascular route of the human body under fluoroscopy, and thus avoiding an open craniotomy procedure, has been a real revolution. It represents a step forward for modern medicine, based on the ability to use current technological advancements and simple human ideas in the services of minimal invasive therapies achieving significant clinical results.

I was fascinated when I first saw the embolisation of a ruptured cerebral aneurysm and the subsequent final outcome of this patient. Furthermore, my enthusiasm has been proved by the clinical reality, and nowadays Endovascular Neurosurgery has the leading role in the treatment of vascular brain lesions worldwide. On the contrary, the daily practice of Endovascular Neurosurgery is not as simple as it may seem. It is definitely based on a thorough knowledge of the central nervous system anatomy and pathophysiology, a detailed understanding of the local angiographic architecture represented in a 3D manner, as well as a huge number of important details which play a significant role in the final outcome. It is important to remember that in this practice, the distance between the success and the disaster is only a few millimeters!

In this rapidly and constantly expanding field of Endovascular Neurosurgery, there are not many teachers or senior and experienced operators available in every unit. Furthermore, the gained experience is relatively limited in both the treatment of the presented vascular pathologies and the continuous evolving materials and techniques, as Endovascular Neurosurgery counts less than two decades of clinical practice. I still remember some of the pioneers of this field, lucky enough to meet and being taught by them, describing that they used to communicate each other (they were less than 15 worldwide) and gather at homes or small country cottages just to exchange their experiences and difficulties and to learn by their own mistakes, asking how you could do it if you were in my position? Of course, all these are just history nowadays, but the need to learn from each other is still vital in our meetings and congresses. This concept returned to my mind when, after completing my 2-year neurovascular fellowship, I returned back home to organize and run a neurovascular unit completely from the scratch. I wished then, I had the chance to ask another neurovascular colleague for his personal opinion on a case, a treatment plan or a complication. Unfortunately, beside the existence of quite experienced neurosurgeons in our team, no other neuroendovascular member was available and no second opinion or idea could be expressed during my neurovascular practice. At all these moments, the appropriate support has been derived either from personal communications or by journal articles or books and their contribution was of paramount importance.

This book has been written based exactly on these thoughts. The theoretical aspects of Endovascular Neurosurgery are already well written by more experienced practitioners and most of the basic techniques can be learned through hands-on experience gained in the angioroom during daily practice. The difficulties and dilemmas appear in searching how to use the available endovascular tools properly, in which cases, under which indications and targets, how to avoid and minimize risks and how to handle the unavoidable complications. The carefully selected presentations included in this book, organized in ten different chapters covering most aspects of endovascular neurosurgery are aimed towards these targets, intended to navigate the reader through practical case-based knowledge contributing to a better understanding of the nature of the CNS vascular lesions and enhance his/her ability to safer and more successful neuroendovascular procedures. The readers who may find this book useful vary from neurosurgeons, neurologists and neuroradiologists in training, neurovascular fellows to more senior practitioners, who would like to compare their personal practice or read the points that are of interest and the sources of difficulties and complications for their neurovascular staff or trainees.

Aristotelis P. Mitsos

Athens, Greece

Acknowledgements

All the patients described in this book have been treated in the Neurovascular Unit of the Department of Neurosurgery in the 401 Athens General Army Hospital by the author himself. Thus, this work and its results are a reflection of the co-operation of the medical, nursing and technologic staff of the Neuroradiology Unit, the ICU and the Departments of Neurosurgery and Anesthesiology. Without their continuous efforts and support, the neuroendovascular service in this hospital could not have reached the quality level it currently offers.

The book is dedicated to my parents for their support throughout my life, to my wonderful wife Maria for her continuous support and to my children, Panos and Rania, who offer me generously the appropriate encouragement to overcome everyday difficulties and move on forward. Last but not least, I would like to thank Andrea Ridolfi of Springer-Verlag for his co-operation and patience in the editorial support throughout this project.

Contents

1 Embryology of the Central Nervous System (CNS) Vascular Network 1

1.​1 Embryological Development of CNS:​ The Basic Features 1

1.​1.​1 The Creation of the Primitive Streak 1

1.​1.​2 The Formation of the Notochord 2

1.​1.​3 The Neural Plate 2

1.​1.​4 The Neural Tube 2

1.​1.​5 The Neural Crest 2

1.​1.​6 Development of the Spinal Cord 3

1.​1.​7 Development of the Brain 3

1.​2 Embryology of the Cranial Arterial System 3

1.​2.​1 The Primitive Aortic Arches 3

1.​2.​2 The Development of the Anterior Circulation 5

1.​2.​3 The Development of the Posterior Circulation 6

1.​3 Embryology of the Cranial Venous System 8

Suggested Reading 10

2 Anatomy of the Central Nervous System (CNS) Vascular Network 11

2.​1 The Cranial Arterial System 11

2.​1.​1 The Internal Carotid Artery 11

2.​1.​2 The Anterior Cerebral Artery 12

2.​1.​3 The Middle Cerebral Artery 13

2.​1.​4 The Posterior Cerebral Artery 14

2.​1.​5 The Vertebral Artery 15

2.​1.​6 The Basilar Artery 16

2.​1.​7 The External Carotid Artery 18

2.​1.​8 The Internal Maxillary Artery 19

2.​2 The Cranial Venous System 19

2.​2.​1 Extracranial Veins 20

2.​2.​2 Dural Venous Sinuses 21

2.​2.​3 Intracranial Intradural Venous System 22

Suggested Reading 26

3 Aneurysms of the Anterior Brain Circulation 29

3.​1 Sidewall Aneurysms 29

3.​2 Bifurcation Aneurysms 64

3.​2.​1 Anterior Communicating Artery Aneurysms 64

3.​2.​2 Middle Cerebral Aneurysms 92

Suggested Reading 105

4 Aneurysms of the Posterior Brain Circulation 107

4.​1 Sidewall Aneurysms 107

4.​2 Bifurcation Aneurysms 114

Suggested Reading 119

5 Brain Arteriovenous Malformations 121

Suggested Reading 142

6 Brain Dural Arteriovenous Fistulas 145

Suggested Reading 154

7 Carotid-Cavernous Fistulas 155

Suggested Reading 161

8 Intracranial Arterial Stenosis 163

Suggested Reading 167

9 Spinal Vascular Malformations 169

Suggested Reading 176

10 Organization of the Neuroendovascula​r Services 177

Suggested Reading 180

© Springer-Verlag Italia 2015

Aristotelis P. MitsosEndovascular Neurosurgery Through Clinical Cases10.1007/978-88-470-5687-9_1

1. Embryology of the Central Nervous System (CNS) Vascular Network

Aristotelis P. Mitsos¹ 

(1)

Neuroendovascular Department, 401 General Army Hospital, Athens, Greece

The understanding of the CNS embryological development is very important in the study of this very complicated part of the human body. This fact becomes even more important for the development of its vascular structures, the arteries and the veins. Many of the events that happen during their embryological development will play an important and crucial role in many of the pathological identities of the CNS vascular network, either directly (i.e., formation of an arteriovenous malformation) or indirectly (i.e., aplasia of one anterior cerebral artery that will influence the creation of an anterior communicating artery aneurysm). Furthermore, the existence of such embryological variations has to be identified early and taken into account before deciding any therapeutic strategy for vascular lesions of the brain or spinal cord. Thus, a thorough knowledge and understanding of these embryological events is of paramount importance for every medical practitioner who is involved in the diagnosis and treatment of CNS vascular lesions.

1.1 Embryological Development of CNS: Τhe Basic Features

The third week of human development identifies the beginning of a 6-week period of rapid evolvement of the embryo, starting from the embryonic disc, which has been already performed by the end of the second week. Major changes occur in the developing embryo at this stage. The most important of them is the conversion of the bilaminar into the trilaminar embryonic disc, which is composed of three germ layers. The process of germ layer formation, which is called gastrulation, characterizes the start of embryogenesis (formation of the embryo). Gastrulation is first indicated at the end of the first week with the appearance of the hypoblast, continues during the second week with the formation of the epiblast, and is completed during the third week, with the formation of the intraembryonic mesoderm by the primitive streak. The three primary germ layers that compose the trilaminar embryonic disc are called the ectoderm, mesoderm, and endoderm. As the embryo develops, these layers give rise to the tissues and the organs of the embryo.

1.1.1 The Creation of the Primitive Streak

At the beginning of the third week, a thickened linear band of epiblast, known as the primitive streak, appears caudally in the median plane of the dorsal aspect of the embryonic disc. It results from the accumulation of cells of the epiblast, as they proliferate and migrate to the center of the embryonic disc. While the primitive streak elongates by the addition of cells to its caudal end, its cranial end proliferate to form an elevated primitive knot. The proliferation and migration of cells from the primitive streak give rise to the mesenchyme (also called the mesoblast). Cells from the primitive streak spread laterally, cranially, and caudally. Some of these mesenchymal cells aggregate to form a layer between the epiblast and the hypoblast, known as the embryonic mesoderm. Some mesenchymal cells invade the hypoblast and displace most of its cells laterally, forming a new layer known as the embryonic endoderm. The epiblastic cells that remain on the surface of the embryonic disc form the layer called the embryonic ectoderm. The embryonic ectoderm gives rise to the epidermis, nervous system, eye, ear, nose, and enamel of the teeth. The embryonic mesoderm becomes the muscle, connective tissue, bone, and blood vessels. The embryonic endoderm forms the linings of the digestive and respiratory tracts.

1.1.2 The Formation of the Notochord

From the primitive knot of the primitive streak, mesenchymal cells migrate cranially under the embryonic ectoderm, forming a midline cellular cord known as notochordal process, which gradually is transformed to the notochord.

The notochord defines the primitive axis of the embryo and gives it some rigidity. During later development, the vertebral column forms around the notochord. By the end of the third week, the notochord is almost completely formed and extends from the oropharyngeal membrane cranially to the primitive knot caudally. The notochord degenerates and disappears during the fetal period in those locations where it is incorporated in the bodies of the vertebra. However, it persists between the vertebrae to form the nucleus pulposus of each intervertebral disc.

1.1.3 The Neural Plate

As the notochord develops, the embryonic ectoderm lying over both the notochord and the adjacent mesenchyme thickens to form the neural plate. It is the developing notochord and the mesenchyme adjacent to it induces the overlying embryonic ectoderm to form the neural plate, the primordium of the brain and the spinal cord. The neural plate first appears near the primitive knot, but as the notochord process elongates and the notochord forms, the neural plate enlarges and invaginates along its central axis to form a neural groove, which has neural folds on each side of it.

1.1.4 The Neural Tube

By the end of the third week, the neural folds have approached each other in the median plane and fused, converting the neural plate into a neural tube. The formation of this tube begins near the middle of the embryo and progresses towards its cranial and caudal ends. The region where closure of the neural tube initially occurs corresponds to the future junction of the brain and the spinal cord. At first, the neural tube has open ends called the rostral and caudal neuropore. The rostral neuropore closes on or before day 26 and the caudal neuropore closes before the end of the fourth week.

1.1.5 The Neural Crest

As the neural folds fuse to form the neural tube, some neuroectodermal cells, which lie along the crest of each fold, migrate ventrolaterally on each side of the neural tube. Initially, these cells form an irregular elongated mass called the neural crest, located between the neural tube and the overlying surface ectoderm. The neural crest soon divides into right and left parts that migrate to the dorsolateral aspects of the neural tube. Neural crest cells migrate widely in the embryo and give rise to the spinal ganglia and the ganglia of the autonomic nervous system. They also contribute to the ganglia of some cranial nerves and form the sheath of the peripheral nerves. Neural crest cells form also the meninges of the brain and the spinal cord and give rise to pigment cells for the development of several skeletal and muscular components of the head.

1.1.6 Development of the Spinal Cord

The neural tube consists of three cellular layers. Nearest to the lumen is a thin ventricular zone (ependymal layer). External to this layer is the thick intermediate zone (mantle layer) and on the outside is the marginal zone (marginal layer). Cells in the ventricular zone divide and produce two types of daughter cells: neuroblasts (future nerve cells) and glioblasts (future neuroglial cells). Both cells complete their differentiation in the intermediate zone of the neural plate.

Laterally, on each side, there are two accumulations of cells in the wall of the neural tube (the developing spinal cord) that are separated by a shallow groove called the sulcus limitans. The mass of cells dorsal to this groove is called the alar plate. The neurons that develop from neuroblasts in the alar plates are predominantly afferent or sensory. The mass of cells ventral to the sulcus limitans is known as the basal plate, and the neurons that develop from neuroblasts in this area are predominantly efferent or motor. The cells in the alar plates give rise to the dorsal or posterior horn of gray matter. The basal plate gives rise to the ventral or anterior horn of gray matter. The enlarging ventral horns of gray matter bulge ventrally, creating the ventral median fissure. The dorsal horns of gray matter approach each other, creating the dorsal median septum and obliterating the dorsal half of the lumen of the neural tube. This creates the central canal of the spinal cord.

For the first 12 weeks, the spinal cord is coextensive with the vertebral column so that the nerve roots pass directly into the intervertebral foramina. However, during later prenatal and postnatal development, growth rates between the spinal cord and vertebral column become different. As the cranial end of the spinal cord is attached to the brain, its caudal end progressively ascends in the vertebral canal. As a result, the conus medullaris in newborn infants is already located at the level of the third lumbar vertebra to become even higher (about L1 level) in adults.

1.1.7 Development of the Brain

Even before the neural tube forms, the neural plate is expanded rostrally where the brain will develop. As the neural tube forms and the rostral neuropore closes, the thickened neural folds fuse to form the three primary brain vesicles: the forebrain (prosencephalon), midbrain (mesencephalon), and hindbrain (rhombencephalon). The development of the head fold in the fourth week produces a cervical flexure in the neural tube near the junction of the hindbrain and the future spinal cord. As the brain vesicles enlarge, two other flexures form: the midbrain flexure in the midbrain region and the pontine flexure in the hindbrain region.

1.2 Embryology of the Cranial Arterial System

1.2.1 The Primitive Aortic Arches (Fig. 1.1)

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Fig. 1.1

From the primitive six pairs of aortic arches to the final aortic arch with its main branches

The most typical feature in the development of the head and neck is the formation of the branchial or pharyngeal arches, which appear in the 4th and 5th weeks of gestation, contributing greatly to the characteristic external appearance of the embryo.

Each branch receives its own cranial nerve and artery, respectively. These arteries are known as aortic arches, arising from the aortic sac, the most distal part of the truncus arteriosus, and terminating in the paired dorsal aortae. These embryonic vascular arches appear initially as undifferentiated plexiform networks in a craniocaudal sequence, forming gradually six primitive arterial arcades around their respective branchial arches, which, however, are not all present at the same time. As an example, by the time the sixth pair of aortic arches has been formed, the first two have already disappeared.

During the sixth to eight weeks, the primitive aortic arch pattern is transformed into the adult arterial arrangement. The aorticopulmonary septum divides the outflow channel of the heart into the ventral aorta and the pulmonary arteries. The aortic sac then forms the right and left horns, which subsequently give rise to the brachiocephalic artery and the proximal segment of the aortic arch, respectively.

The first pair of aortic arches appears at about 24 days of fetal development. These vessels largely disappear, but the remaining parts form the mandibular arteries and can also contribute to the development of external carotid arteries.

The second pair of aortic arches appears by day 26, as the first pair regresses and, similarly, will soon disappear. The proximal part of these vessels, the hyoid arteries, persists as stem for the development of the stapedial arteries and may later contribute to the formation of external carotid arteries.

The third pair of aortic arches appears by day 28, while the embryo is 4 mm.

The proximal parts of these arteries form the common carotid arteries, while the distal portions join with the dorsal aortae to give rise to the internal carotid arteries.

The fourth pair of aortic arches appears also on day 28. It persists on both sides, but its ultimate fate is different between the right and left sides. On