для читателей старше 18 лет
Olga Benuanovna Belousova
Neurologist, Dr. Med. Sci., leading research scientist in the Clinical Vascular Neurosurgery Department of FSAI «Burdenko Neurosurgery Institute» of the Ministry of Healthcare of the Russian Federation
Anton Evgenyevich Korshunov
Neurosurgeon, Cand. Med. Sci., senior research scientist in the Clinical Pediatric Department of FSAI «Burdenko Neurosurgery Institute» of the Ministry of Healthcare of the Russian Federation
Irina Andreyevna Nagorskaya
Medical Psychologist, Cand. Psych. Sci., Medical Psychologist in the Mental Research Team of FSAI «Burdenko Neurosurgery Institute» of the Ministry of Healthcare of the Russian Federation
Vasiliy Andreyevich Lukshin
Neurosurgeon, Cand. Med. Sci., senior research scientist in the Clinical Vascular Neurosurgery Department of FSAI «Burdenko Neurosurgery Institute» of the Ministry of Healthcare of the Russian Federation
Olga Aleksandrovna Lvova
Pediatric Neurologist, Dr. Med. Sci., assistant professor in Chair of Psychiatry, FSBEI of Higher Professional Education «Urals State Medical University» of the Ministry of Healthcare of the Russian Federation, leading research scientist in the Laboratory of Brain and Neurocognitive Development of FSAEI of Higher Professional Education «Ural Federal University named after the first President of Russia B.N. Yeltsin»
Olga Borisovna Sazonova
Neurophysiologist, Cand. Med. Sci., leading research scientist in the Laboratory of Clinical Neurophysiology of FSAI «Burdenko Neurosurgery Institute» of the Ministry of Healthcare of the Russian Federation
Elena Viktorovna Shevchenko
Neurosurgeon, Cand. Med. Sci., junior research scientist in the Clinical Vascular Neurosurgery Department of FSAI «Burdenko Neurosurgery Institute» of the Ministry of Healthcare of the Russian Federation
Lyudmila Valentinovna Shishkina
Pathomorphologist, Cand. Med. Sci., Head of Laboratory of Pathomorphology in FSAI «Burdenko Neurosurgery Institute» of the Ministry of Healthcare of the Russian Federation
Dmitry Yuryevich Usachev
Neurosurgeon, Corresponding Member of the Russian Academy of Sciences, Dr. Med. Sci.,Prof., Deputy Director for Science of FSAI «Burdenko Neurosurgery Institute» of the Ministry of Healthcare of the Russian Federation
List of acronyms and conventional symbols
ABP — arterial blood pressure
ACA — anterior cerebral artery
ACVD — acute cerebrovascular disease
ADHD — attention deficiency and hyperactivity
ADP test — adenosine diphosphate induced
platelet aggregation test
AHT — arterial hypertension
ASA — acetylsalicylic acid
ASL — Arterial Spin Labeled
ASPI test — arachidonic acid induced
platelet aggregation test
BCA — brachiocephalic arteries
CAG — cerebral angiography
CCA — common carotid artery
CCVD — complete cerebrovascular disease /
CN — cerebral nerves
CNS — central nervous system
CO — cerebral oximetry
CPISR — Canadian Pediatric Ischemic Stroke Registry
CVD — cerebrovascular disease
CVS — cardiovascular system
DEP — dyscirculatory encephalopathy
DMB — dura mater of brain
ECA — external carotid artery
ECG — electrocardiography
EchoCG — echo-cardiography
EDAS — encephalo-duro-arterio-synangiosis
EDMS — encephalo-duro-myo-synangiosis
EEG — electro-encephalography
EICMA — extra-intracranial microvascular
EMS — encephalo-myo-synangiosis
ICA — internal carotid artery
INR — international normalized ratio
IS (AIS) — ischemic stroke (arterial ischemic stroke)
LBFR — linear blood flow rate
MASGS — Modified Ashworth Scale of
MCA — middle cerebral artery
MONICA — The World Health Organization’s
Multinational Monitoring of Trends and
Determinants in Cardiovascular Disease
MRA — magnetic resonance angiography
MRI — magnetic resonance imaging
NIHSS — National Institutes of Health Stroke Scale
NSA — National Stroke Association
OA — occipital artery
PCA — posterior cerebral artery
PComA — posterior communicating artery
PET — positron emission tomography
PS — pial synangiosis
SCT AG — spiral computed angiography
SCT or CT — spiral computer tomography
STA — superficial temporal artery
TCUSDG — transcranial ultrasonic dopplerography
TIA — transitory ischemic attacks
US — ultrasonography
VBS — vertebrobasilar system
WHO — World Health Organization
Pediatric stroke. Revascularization and reconstructive surgery in children
Pediatric stroke is one of the most widely discussed problems in contemporary medicine. This is, primarily, associated with the fact that a cerebral vascular disease (CVD) is considerably less common in childhood than in adults, and, therefore, less known. At the same time, children, who had suffered CVD, constitute an essential group among disabled children. This determines the need for a closer study of the pediatric stroke problem, particularly, in the background of successful conservative and surgical treatment of strokes in adult population.
The spectrum of clinical manifestations of the pediatric stroke is wide enough — from mild focal and isolated general cerebral symptoms to the formation of a significant neurologic deficiency with a predisposition to recurrence with the subsequent sustained disability and a high risk of fatality. Thanks to a widespread distribution and technical improvement of neuroimaging methods, the pediatric stroke is diagnosed with the ever increasing frequency. Nevertheless, the low awareness of neurologists about the CVD problem in childhood, including the transitory ischemic attacks (TIAs), frequently leads to difficulties in diagnostics and, consequently, to delayed and insufficient medical aid. Due to the variety of reasons, clinical manifestations and the course of the pediatric stroke, selecting the patient management approach becomes difficult, especially, in neurology and brain surgery departments in small city hospitals, where medical specialists lack sufficient experience in treatment of this disease.
This book presents basic literature data on etiology, pathogenesis, clinical manifestations of a pediatric stroke, examination methods and approach to the conservative and surgical treatment of acute and chronic cerebral ischemia in children as well as our own studies on diagnostics and results of conservative and surgical treatment of children with the disease onset at the age of the 1-st day of life up to 18 years old, all obtained on the basis of Burdenko Neurosurgery Institute and FSBEI of Higher Professional Education «Urals State Medical University» of the Ministry of Healthcare of the Russian Federation.
This book will enable a wide range of pediatric specialists to get an idea about the specific features of a pediatric ischemic stroke, its diagnostics, conservative treatment principles and options for surgical treatment of this disease.
Pediatric stroke. General information
Nowadays, the mortality rate of cerebrovascular diseases in Russia is one of the world’s highest. A cerebrovascular disease holds one of the first places among the most frequent mortality and disability causes, just as in economically developed countries too. The World Health Organization’s Multinational Monitoring of Trends and Determinants in Cardiovascular Disease (MONICA) determines the course of a stroke as «a sudden neurologic deficiency sustaining for over 24 hours, or a sudden death». This definition includes both ischemic and hemorrhagic strokes .
In a pediatric population, an ischemic stroke is a less frequent pathology as compared to the adult population. Strokes occur in children of any age . Delayed or erroneous diagnosis of a stroke in children still remains a common enough event [80; 104].
The descriptions of individual clinical cases of cerebrovascular diseases in children can be found in literature since the 17-th century. The first description of a stroke in a child is considered to be made by T. Willis in 1667. J. Wepfer (1658) mentioned sick children, who had a hemiplegia, which was emerging and regressing within a day or faster . The disease termed as «an infantile hemiplegia» was presented in the works by W. Osler (1889), B. Sachs and F. Peterson (1890) as well as S. Freud (1893) in a series of pediatric patients, who had suffered a stroke. It was only in 1927 that F. Ford and A. Schaffer published the first ever systematized description of methods for assessment and treatment of children with ischemic strokes. The authors analyzed the etiology of a pediatric stroke as well as the methods and the results of treatment, which had a subsequent effect on the quality of life . V. Hachinski (1982) described non-specific symptoms, such as a headache and syncopes . It is important to note that many problems outlined by them still remain pertinent even today.
The works by M. Norman (1957), C. Fischer (1959), E. Frantzen (1961), E. Bickertaff (1964), J. Jackson (1970), J. Abraham (1971), W. Kannel (1972) about pediatric strokes are, doubtless, interesting, although these publications did not contain any mentioning of the transient cerebrovascular diseases in childhood . In later studies, the transient cerebrovascular diseases, or, in other terms, the transitory ischemic attacks (TIAs), were noted to occur in children much more frequently than strokes . In 2006 G. Ganesan et al. published an article on the results of a retrospective (from 1978 to 1990) and prospective (from 1990 to 2000) survey of children, who had suffered a stroke, with the use of a neuroimaging. They described 212 patients, including 97 ones with an erroneous initial diagnosis. 79 children were noted to have a growing neurologic deficiency (29 strokes, 46 TIAs, 4 fatal cases due to a recurrent stroke), while during the analysis of the subsequent 5 years 51 children (67%) were noted to have recurrent episodes of cerebrovascular diseases .
The number of publications on the subject of a pediatric stroke is growing worldwide with every year. In recent years, educational seminars and topical sessions on this problem appeared in the European Stroke Organization Congress program (Nice, 2014; Glasgow, 2015; Barcelona, 2016). Nowadays, practitioners working abroad can be guided by two manuals: an American one — «Management of Stroke in Infants and Children» released in 2008 and a European one — «Stroke and cerebrovascular disease in childhood» published in 2011 in London [105; 267]. Thus, practical manuals accumulating the results of scientific research and permitting to make clinical decisions are solitary and rarely updated.
The lack of universally accepted international recommendations or guidelines hampers the choice of approaches to treatment and prevention of pediatric strokes. A low awareness of pediatric neurologists on the problem of pediatric strokes and TIAs often leads to difficulties in diagnostics and inadequate therapy of pediatric patients and, therefore, to a delayed and inadequate care, which was noted by V.P. Zykov (2008), F. Kirkham (2011) and A. Mallick (2014) in their works. The main drawback of the research studies presented in literature consists in the fact that only some individual states were specified as those relevant to risks, which, as a rule, was determined by the specialty of a research team (infectologists, rheumatologists, geneticists, hematologists, etc.). The paucity of assessed sampling children in these studies and the restriction of data acquisition to a specific age group (infants, teenagers, etc.) hampered the potential generalization of results obtained within the boundaries of all age groups.
The rate of strokes in the adult population of the Russian Federation is about 500,000 cases per annum, the average stroke morbidity rate is 4.6 incidents per 1,000 of the population annually (the NSA data, 2003).
According to literature data, the average global pediatric stroke morbidity rate varies within a range of 0.93 — 13 incidents per 100,000 of the population annually . According to data of the American Heart Association & American Stroke Association, 2012, the highest stroke incidence rate is noted during the first year of life — approximately 1 incident per 4,000 liveborns . The stroke morbidity rate in children aged from 0 to 15 years in the USA is 6.4 incidents per 100,000 children . During the last 10 years, this number remained stable, but the recent research showed that the incidence rate was 3—4 times higher, than it had been stated earlier .
M. Giroud et al. (France, 1995) report that in children below 16 years old the CVD incidence rate reaches 13 incidents per 100,000 children annually. This number includes 7.9 cases of ischemic CVD per 100,000 children and 5.1 cases of hemorrhagic CVD .
According to data of the Canadian Pediatric Ischemic Stroke Registry (CPISR), in 2000 this parameter was recorded at the level of 2.7 incidents per 100,000 annually . F. Kirkham et al. reported that in 2004 the incidence rate of CVD in British children was 13 incidents per 100,000 of pediatric population .
Thus, according to various data, the morbidity rate of pediatric hemorrhagic stroke at the age from 1 month to 18 years varies from 1.5 to 5.1 (on the average, 2.9) and that of the ischemic stroke — from 0.6 to 7.9 incidents per 100,000 of the population annually. Also, there are some data on the percentage ratio of these two types of strokes: 55% is accounted for ischemic strokes and 45% — for hemorrhagic ones . At the same time, in newborns this parameter is considerably higher for both types of CVD: 6.7 and 17.8 per 100,000 of the population annually for hemorrhagic and ischemic types of CVD respectively [11; 167; 215].
These figures show that, generally, the ischemic stroke incidence rate in children is higher than the hemorrhagic one, although this difference is not as big as in adults [8; 33; 40], which makes the CVD structure in children essentially different.
During the period from 1979 till 1998, in the USA the child mortality decreased by 58%. Such a decrease is deemed to occur due to the improvement of the treatment quality, not due to the drop in stroke morbidity rate . According to latest data, from 20% to 40% of children die after the strokes in the USA , and the stroke is among ten leading causes of child mortality ; about 3,000 children and teenagers (below 18 years old) suffered a stroke in 2004 ; during the period from birth to an age of 18 years old the stroke risk is almost 11 incidents per 100,000 children annually ; strokes occur in boys approximately 1.3 times more frequently than in girls ; in Afro-American children the stroke risk is higher than in children from Europe and Asia .
The stroke mortality in children varies from 7% to 28% [100; 161], being higher in hemorrhagic strokes (up to 40%) than in ischemic ones (8—16%). The fatal outcome usually occurs in the early rehabilitation period, which is deemed to be the most dangerous time for recurring acute vascular episodes and patient death. Such indicators in children with ACVD are, generally, consistent with the statistical data on adults. However, the mortality level of 10%-40% may be regarded as the highest-ever for pediatric practice, which permits to determine strokes in this age group as one of the emergency pathologies threatening with fatal impairment of vital functions.
The official statistics on pediatric stroke morbidity rate in our country are not available . In literature there are some data for individual areas or institutions. Specifically, based on an example with one of the central regions of Russia, V.M. Delyagin et al. (FSI «Federal Research & Clinical Centre of Pediatric Hematology, Oncology and Immunology», Moscow) reported that during the period from 2006 to 2009 the ACVD morbidity rate among children (excluding newborns) was from 0.93 to 1.1 incidents per 100,000 children annually. When estimating the number of children and teenagers with strokes per total number of children taken to multidisciplinary children’s hospitals, the stroke incidence rate is 3.5 per 1,000 patients annually [7; 11], which corresponds to data of foreign multi-center surveys. This number includes 2.8 children aged from 0 to 11 years old per 1,000 patients annually and 0.7 children aged from 12 to 17 years old (teenagers) per 1,000 annually; the average pediatric stroke morbidity rate (from 1 month to 18 years old) is about 8 incidents per 100,000 of population annually. The mortality among children with CVD reaches 0.6 per 100,000 of population annually .
Having analyzed the data on 143 patients aged from 0 to 17 years old with CVD (the age median of 5 years old, in 68 boys (48%) and 75 girls (52%)), the same authors concluded that all types of CVD occur equally often both in boys and girls, with the exception of TIAs, which are recorded in girls three times more frequently than in boys. The authors also note a high percentage (13%) of recurrent strokes in children, while the highest risk of a recurrent CVD is recorded during the first 2 weeks after the disease onset .
According to data of the Emergency Call Service of Moscow, in 2012 there were 157 ambulance responses on calls to children and teenagers with the ACVD diagnosis, and in 2013 — 179 .
Employees of the FSBEI of Higher Professional Education «Urals State Medical University» analyzed the stroke in children living in the area of Yekaterinburg (with population of 1.5 million people) and Sverdlovsk region (4.5 million people). The following parameters were assessed: the stroke registration rate in the years from 1995 till 2015; the morbidity rate during the last five years, including children of the first year of life; gender distribution characteristics; incidence rate of fatal outcomes and recurrences in 162 children with IS and 73 children with TIA.
The study was held for 10 years. During this period, the information was distributed among the pediatric neurologists of the city and the region, who actively referred already followed-up and new pediatric patients with diagnosed or suspected ischemic ACVD to hospitals. We suppose that practically all patients with the onset of IS or TIA occurring in childhood were included into this database, and this permits to regard this study as an epidemiological survey.
According to the data obtained, during the last five years the morbidity rate was: 3.4 (2011), 4.9 (2012), 4.9 (2013), 4.6 (2014) and 5.0 (2015) per 100,000 of the pediatric population annually. Fig. 1 shows the total number of registered children with strokes on a specified territory during the last 20 years since 1995, when neuroimaging (brain CT) and emergency diagnosing became possible.
It must be emphasized that the obtained indicators are closer to the lower threshold of values stated in literature (2—26.7 per 100,000 annually). At the same time, a distinct tendency for growing stroke registration incidence rate in children in the surveyed area, which can be observed during the last ten year period in all countries, where ACVD morbidity is registered among children.
The average age of children with IS manifestation at the age of below one year was 19.5±1.2 weeks (we revealed 7 infants with fetal / perinatal onset of IS) and at the age of above one year — 6.2±0.4 years. For TIA this parameter was 11.8±0.3 years.
The gender distribution of patients was even, and matched the literature data: boys with IS constituted 62.7% (n=102), and boys with TIA — 45.2% (n=33).
Based on literature data, the average risk of recurrent strokes in children is 20%, while in children with a single revealed risk this parameter is within 8%, and in children with a combination of two or more risks it grows at an exponential rate and reaches 42% [145; 148].
According to data of the FSBEI of Higher Professional Education «Urals State Medical University», the recurrence is also recorded on the levels of 14.2% (n=23) and 70.4% (n=50) for IS and TIA respectively. The average incidence rate of recurrent ISs was 1.6±1.1 (1–2 episodes of IS compared to 2–19 incidents of TIA), the average incidence rate of TIA was 3.4±0.5 incidents (from 2 to 20 episodes). It is the low level of ACVD detectability in childhood, which is supposed to cause the lack of timely and comprehensive examination, correct diagnosing and timely application of secondary prevention measures. For example, there was a patient registered, who had suffered 6 TIAs and 2 ISs, before he was subjected to a comprehensive examination, which diagnosed the moya-moya disease.
The disability status was given to 61.2% (n=90) and 9.1% (n=4) of patients from 125 and 62 children with IS and TIAs respectively, whose catamnesis was known. It should be noted that the disability in the group of children with TIAs was caused by a non-neurologic deficiency: two children had an acknowledged moya-moya disease, one had a chronic renal insufficiency, and one — a congenital heart defect.
The mortality in a group of children with IS was 3.3% (n=4, 2 boys and 2 girls); all the patients, who had suffered TIAs, were alive by the moment of the last follow-up visit (minimum 2 years of follow-up).
Thus, the literature data and the results of limited epidemiological surveys in Russia permit to conclude that ischemic strokes are a relatively rare disease in pediatric practice, although they are characterized by a high rate of recurrence, disability and mortality.
2. Pediatric stroke classifications
As already stated above, the ratio between hemorrhagic and ischemic strokes in children essentially differs from that in an adult age group. There is no unanimous opinion on the ratio between these variants in children. Apparently, the prevalence of an ischemic or a hemorrhagic ACVD variant in every new survey is associated with the specialization profile and medical care type in a healthcare facility.
Also, there are discrepancies in determination of a stroke variant in a child. For instance, the national research community failed to agree whether periventricular ischemia as well as intraventricular and subarachnoid hemorrhages can, by way of a morphological substrate of perinatal impairment of infants’ nervous systems, be considered to be equivalents of ischemic or hemorrhagic ACVDs (by analogy with adult patients). Authors of foreign clinical manuals on diagnostics and treatment of strokes say that they excluded infants with such lesions from analyzed literature sources. Based on provided epidemiological indicators, it also becomes evident that the researchers did not include patients with perinatal encephalopathy into their analysis scope [183; 107; 146; 220; 280].
It is well known that an ischemic stroke is broken up into the following categories:
• complete stroke — a cerebrovascular disease, which results in the formation of a sustained neurologic deficiency; ischemic lesions of cerebral tissue are detected by spiral computed tomography (CT) and magnetic resonance imaging (MRI) of brain;
• minor stroke — an acute development of a neurologic deficiency with subsequent complete regression within 2—3 weeks; small ischemic lesions may be detected by CT and MRI of brain;
• evolving stroke or stroke in evolution — an acute development of cerebral ischemia accompanied by a gradual growth of the neurologic deficiency during several days.
A separate nosological form of ACVD is transitory ischemic attacks (TIAs), which are characterized by a sudden development of a neurologic or retinal deficiency of ischemic nature, which is related to a specific artery territory and which regresses completely within 24 hours. TIAs occur considerably more frequently than strokes. Regarding their incidence rate, TIAs are subdivided into rare (1—2 times per year), mid-frequent (3—6 times per year) and frequent (once per month or more frequently) . TIAs may be a manifestation of a chronic cerebral ischemia (insufficiency) with a high risk of subsequent development of a massive IS. Thus, a TIA may be considered an antecedent of IS.
The international terminology used for describing a pediatric stroke includes the following notions:
1. fetal (prenatal, intra-uterine) stroke — before the child birth;
2. perinatal stroke (when the disease develops during the period from the 28-th gestational week till the end of the first month following the birth);
3. pediatric stroke — at the age of 1 month following the birth until 18 years old [37; 148].
Presently, in children it is proposed to single out the following pathogenetic types of an ischemic stroke: hemodynamic, metabolic, embolic and occlusive.
There is no generally accepted and acknowledged by all specialists classification of CVDs in children. Above, we have presented a classification, which considers the age, when the stroke onset occurred.
Regarding the periodization of the disease itself, national specialists prefer to rely on the time frames formed in adult practice.
Groups of experts attempt to propose the pathogenetic variants of a pediatric stroke classification, yet they fail to end the discussions. For instance, they propose an anatomical classification named CASCADE (Childhood AIS Standardized Classification and Diagnostic Evaluation), which considers the localization and/or source of thrombosis/embolism of brain arteries (minor cerebral arteries, major cerebral arteries, aorta and cervical arteries, heart) . The development of CASCADE classification was aimed at creating an analog of TOAST (Trial of ORG 10172 in Acute Stroke Treatment) accepted in adult practice, which was practically achieved . However, the criteria specified in it can be hardly met or, in fact, cannot be met at all: e.g., they imply a histological acknowledgement of changes in cerebral vessels. Another essential drawback of this classification is deemed to be ignoring the embolic variant of IS and thrombophilic states in it.
3. Aetiopathogenesis and risks
A pediatric stroke is heterogeneous in aetiopathogenesis. If in adults strokes are associated most frequently with atherosclerosis of brachiocephalic arteries (BCA) [26; 27], the etiology of strokes in children is diverse and complex . In literature there is a quite exhaustive list of diseases and syndromes, which are fraught with a risk of cerebral ischemia in childhood, adolescence and youth. According to data of the American Heart Association & American Stroke Association (2012), half of all children, who had suffered a stroke, had risks .
Complexity and diversity of etiology imply a wide circle of specialists, who must keep an alert eye on strokes in their routine practice.
Heart diseases (congenital and acquired) present one of the most significant risks equal to about 20—30% of the causes of ischemic strokes in childhood . A combination of left-heart embolisms (or paradoxical embolism in right-to-left cardiac shunt) and cardiac decompensation is important in pathogenesis of cardioembolic variant of an ischemic stroke [1; 7; 22; 52]. There is a description of cases of paradoxical embolism into the cerebral vessels of children and young people in the background of an atrial septal defect, open foramen ovale, in cases of arteriovenous malformations of pulmonary vessels and neurocutaneous syndromes . While this problem was in focus, the attention was again attracted to minor cardiac abnormalities. Regarding patients with vague etiology of stroke, it is, primarily, recommended to rule out sources of hidden or paradoxical embolism as an open foramen ovale, a mitral valve prolapse and an atrial septal aneurysm [1; 52; 56; 38]. The literature data state that imaging reveals «silent» brain infarctions in 25% of patients with mitral stenosis. Also, clinically «silent» ischemic lesions of brain tissue are found in 20% of newborns with heart diseases on a pre-surgery stage and in 17.4% — on a post-surgery stage [63; 181; 221]. Presently, several studies were held with the attempted prognostication of strokes in infants with congenital heart diseases. A significant role of duration and an intensity of hypoxia in newborns, resuscitation procedures, prematurity and duration of waiting for surgical intervention were indicated as ACVD risks at pre-surgery and post-surgery stages [62; 112; 161; 181; 183; 210].
Cardiac arrhythmias are considered to be a very rare cause of strokes in childhood and youth, as opposed to adults. Nevertheless, it should be kept in mind regarding children with hyperthyreosis, rheumatic heart diseases, after surgical interventions and in the structure of Kearns-Sayre syndrome.
Cardiac myopathy as a manifestation of systemic diseases occurs in congenital myopathies (Duchenne, Becker, Emery-Dreifuss, etc.), Friedrich’s ataxia, mitochondrial diseases. With this pathology, both embologenic and hemodynamic variants of an ischemic stroke are possible. In some cases, a myocardial infarction and a stroke may develop simultaneously, which points at the similarity of pathogenetic processes leading to inadequate perfusion .
Hypercoagulation states are presently considered to be the most common causes of ischemic strokes in childhood — their contribution reaches 87% [3; 16; 138; 144; 170; 265]. However, a universally acknowledged screening protocol for thrombophilic state in a child with CVD has not been developed yet, and some researchers dispute the role of multigenic thrombophilias as risks of strokes and TIAs in children [82; 121; 142; 184; 194; 282].
During the last decade a large number of thrombophilic mononucleotide genic polymorphisms were described. Carriership of proaccelerin, prothrombin, plasminogen activator inhibitor and fibrinogen is considered to be most significant clinically [61; 138]. F5 genotypes: 1691 G> A and AA (Leyden mutation) as well as F2: 20210 G> A and AA are currently the only ones, whose prothrombotic effect is acknowledged in newborns. Besides, there is a good reason to suppose that with the carriership of thrombogenic mutations and polymorphisms in children the risk degree differs according to their age [5; 56; 138].
Presently, there are no doubts regarding the connection of hyperhomocysteinemia and MTHFR677C> T mutation with cerebrovascular and cardiovascular diseases [5; 16; 61; 280]. Homocystein acts as a prothrombotic factor due to activation of coagulation factors XII and V, increase in tissue factor expression and suppression of thrombomodulin expression. Besides, the rise of homocystein in blood leads to vascular endothelium damages, which reveals in neurotoxic and proatherosclerotic effects and contributes to the emergence of resistance to activated protein C [3; 31; 66; 267; 276; 290]. During the latest years, the role of hyperhomocysteinemia in damaging the vascular walls was proven as well as its prothrombotic and pro-atherosclerotic effects and its effect on the vasomotoric regulation [3; 32; 290].
The MTHFR enzyme gene provides for homocystein metabolism with the participation of a folic acid. The greatest practical significance belongs to a mononucleotide replacement of cytosine with thymine at position 677 of gene, thus leading to a replacement of alanine amino acid residue with valine in the catalytic core of methylene tetra hydro folate reductase enzyme (MTHFR). Individuals, homozygous by this allelic mutation, display a decrease of the enzyme activity by 60—70%, and heterozygous — by 35% [28; 159; 275]. It should be noted that all available data concern either fundamental aspects of the pathology study, or the population of adult patients.
According to literature data, children are noted to have a positive correlation relationship between the incidence rate of strokes (especially, in boys) and C677T polymorphism. The combination of several variants of genes is accompanied by a progressive rise of homocystein level in blood, and it increases the risk of a CVD [61; 142; 229; 255; 269; 289]. At the same time, a series of genic polymorphisms controlling the folate cycle activity showed their protective function regarding the cerebrovascular pathology in Asian and European populations [82; 142]. Despite the indirect relationship between pheno- and genotype of hyperhomocysteinemia, the researchers’ opinion is unanimous: determination of the homocystein level and the state of folate cycle genes must become an insatiable component of diagnostic suite in this group of patients, especially, in boys (class II, recommendation level B) .
In the literature there is a description of singular clinical cases of BCA thrombosis in children. There are no general statistics on CCA, ICA and MCA occlusions in pediatric population neither in national, nor in foreign literature. In 1951 M. Fisher was the first to describe the post-thrombotic occlusion formation steps in ICA of adults with hemodynamic and embolic mechanisms of an ischemic stroke, having analyzed the angiograms of patients with CVDs . Post-thrombotic occlusions of major arteries in the heads and necks of children account for from 13 to 37% in the structure of CVD causes.
In childhood there are more than enough initiating agents capable of worsening the hemorheologic situation or decreasing the athrombogenic properties of a vascular wall. The adverse course of the post-natal adaptation period, infection, microtraumatization and metabolic disorders can act as triggering factors and lead to an acute cerebral ischemia in the background of the carriership of mononucleotide polymorphisms in thrombophilic spectrum genes and in the genes, which control the activity of folate cycle enzymes. In children with CVDs (especially, when the onset is in the perinatal period), it is recommended to search for prothrombotic mutations even, when other causes of ACVD are identified (class IIa, recommendation level C) [107; 280]. At the same time, the detection of thrombophilic polymorphisms is not an absolute factor inevitably leading to thromboses. Attention should be paid to the quantity of revealed mononucleotide mutations, the fact of homozygous carriership, the variants of genes — genic combinations and their phenotypic manifestations [5; 121; 286].
If the researchers have no doubts about hyper-homocysteinemia presenting a risk of thrombi formation at a non-typical age, the atherothrombotic variant of CVD is a casuistry for pediatric practice. Such variants are described in singular cases and associated with proven, genetically determined, dyslipidemic syndromes [165; 167; 189], most of which proceed asymptomatically . Nevertheless, the selective screening and the lipid metabolism monitoring are recommended for patients with a family history of an early onset of vascular diseases and for the ones with an unclear cause of the stroke [111; 239].
The significance of the infection process as the releasing factor with the developing acute cerebrovascular insufficiency in the background is great both in newborns (up to 17.6% among all causes) and in elder patients (up to 40.7%) [60; 63; 223; 226; 280]. The clinical study showed the significance of a short duration (up to 4 weeks) and the fact of minor infections as an independent risk, which both enhance the probability of an ischemic ACVD 4.6 times as much [43; 240]. When analyzing the strokes of an unknown etiology, it was noted that shortly before the stroke children had varicella 3 times more often than in the population; the probability of a stroke also remained high within the first four months after varicella [157; 160]. Besides, the study held in 2006 showed that, in children with the earlier revealed immunodeficiency, the risk of the recurring stroke grew 20.9 times as much and correlated directly with the level of white blood cells during the acute period of the disease. A chronic infection and the immunodeficiency are supposed to make their own contribution to the development of recurrent incidents of CVD in children in the same way, as in adults .
It cannot be ruled out that an infectious process flows in the nervous system by the mechanism of vasculitis. Presently, the VIPS study (The vascular effects of infection in Pediatric Stroke Study) is held with the hypothesis stating that the presence of an infectious agent triggers an endothelial dysfunction, a systemic inflammatory process, which, combined with insufficiency of connective tissue and prothrombotic readiness, leads to damages of the vascular wall, its dissection, thrombogenesis, luminal occlusion and cerebral ischemia [13; 101; 127]. Later on, an embolism may occur from the artery dissection site as well as the hemorrhagic transformation of an ischemic lesion [13; 16; 101]. Also, apart from vasculitis, some hemorrhagic complications caused by coagulopathy may occur in severe somatic diseases [54; 55]. Presently, there are no such distinct diagnostic criteria of cerebral vasculitis in children, which could provide grounds to assert with confidence that it was this disease that had caused the CVD . It is proposed to keep in mind that vasculopathy may be the most probable etiology of a CVD in all cases of TIA, and that it happens always in pediatric or young patients, especially, in the absence of evident risks [22; 55; 168].