O. Belousova: Pediatric stroke. Revascularization and reconstructive surgery in children with cerebrovascular disease

Hereditary factors play an important part in the moyamoya disease [196; 277]. There are some known familial cases of the disease. According to some data, this disease has a familial nature approximately in 15% of patients. Due to this, over the latest years the attempts have been made to find a genetic base of the disease. Some data were published on the detection of the locuses associated with the moyamoya disease on 3, 6, 8 and 17 chromosomes. In 2008 some data were published about the autosomal dominant inheritance (the gene was mapped to chromosome 17q25) of the moyamoya disease [119; 130; 197; 199; 225]. However, in the literature there is a description of the moyamoya disease in one of two twins, and this permitted the authors to conclude that this disease was not rigidly determined [256]. In one of their latest works J. Ma et al. report (China, 2013) that while studying the associative genetic predisposition, they have found the connection between the moyamoya disease and genic polymorphisms in RNF213 gene (p.R4859K and p.R4810K), which is more common in Japan and Korea, but less common in China [171].

Despite these studies, the genetic screening in the moyamoya disease has not become widely common, because its efficacy was not proved [233]. As of today, the researchers studying this problem think that this disease has a multi-factor nature [266].

As already stated above, the pathophysiology of the moyamoya disease consists in the gradual constriction of major stems of basilar intracranial arteries due to deposits of lipids in the intima in the absence of inflammation signs. The middle layer of arteries is thinned, the adventitia is not involved into the process. Similar changes in vessels may be observed in other organs, which shows that the vascular impairment has a systemic nature. The involvement of the immune system into the process is not ruled out [270]. In some authors’ opinion, inflammatory proteins participate in the development of the disease [287]. Anyway, intra- and extra-cranial vascular anastomoses are formed on the base of the brain during the progressive occlusion process in the vessels of the Willis’ circle [270; 277], which, to a certain degree, compensates for critical decrease of the regional cerebral blood flow, but leads to a gradual growth of chronic cerebral ischemia mostly in the cortical sections of big hemispheres [208; 266; 291]. The anastomotic capillary network is disappearing, while collaterals are developing from the ECA (meningeal collaterals are called «a magic network») [208; 291]. Arterial aneurysms frequently occur in the moyamoya disease. According to some data, the detection rate of VBS aneurysms reaches 62%, which several times exceeds the incidence of this pathology in the population (5—15%) [196; 270].

The unique character of clinical manifestations of the moyamoya disease and syndrome consists in the fact that this pathology may reveal both as an ischemic CVD and intracranial hemorrhages. Also, both these variants may occur in the same patient during his life [192; 196; 270]. In 1990 Y. Matsushima offered the moyamoya disease classification based on its clinical course:

Type 1: revealing as rare TIAs – 2 times per month or more seldom;

Type 2: revealing as frequent TIAs – 2 times per month or more often;

Type 3: revealing as a minor stroke (with regressive neurologic deficiency within 2—3 weeks). Small ischemic lesions may be found on a brain CT;

Type 4: revealing as a progressive stroke (gradual growth of neurologic deficiency with time);

Type 5: revealing as a complete stroke resulting in the formation of a persistent neurologic deficiency; extensive ischemic lesions are found on the cerebral tissue during the brain CT and MRI.

Types 1—5 are referred to ischemic variant of the disease course.

Type 6: the disease reveals as a hemorrhagic CVD due to a rupture of anastomotic network vessels [178].

C. Mohanty et al. (India, 2013) report 11 incidents of an unusual course of the moyamoya disease, when both hemorrhagic and ischemic CVD lesions are noted in the same hemisphere of a patient either simultaneously or at different periods of time [186].

According to foreign data, the moyamoya disease mortality is higher in adults than in children (10 and 4.3% respectively). Hemorrhages were the cause of death in 56% of 9 perished children. With the surgical treatment a favorable prognosis is noted in 58% of cases [268].

Clinical manifestations of acute cerebrovascular diseases in the carotid system of children are typical enough, and they reveal in a focal neurologic deficiency with developing motor disturbances (87—95%), disturbances of speech, sensibility and vision as well as other symptoms corresponding to the location of cerebral tissue lesions. In massive strokes during the acute period of the disease, as a rule, general neurological symptoms are more marked, which is caused by edema and dislocation of the brain. When the ischemic zone is small, the focal symptoms develop in the background of the generally normal state. The clinical picture of a cerebrovascular disease in a child may be atypical: nausea, vomit and depression of consciousness may be replaced with agitation or body temperature rise and convulsions (19—58%).

For obtaining more objective data on the severity of clinical manifestations of the ACVD and assessing the neurologic deficiency changes in acute and rehabilitation periods of the stroke, the PedNIHSS (Pediatric National Institute of Health Stroke Scale) scale is used, which has showed its consistence with the NIHSS scale [175; 235]. During the period of residual effects, American researchers apply the PSOM scale (Pediatric Stroke Outcome Measure) [37; 107]. These scales are rather extensive, but easy to fill in, so they can be automated and introduced into the patient examination standard. The obstacle for their implementation in the RF territory is the need for training of specialists in the estimation methodology proper as well as the need for validation of evaluation and measurement scales.

A paroxysmal syndrome often becomes the first symptom of any type of a CVD in children. More frequent registration of the paroxysmal syndrome is noted in the infant group [60; 69; 81; 291]. In children, the paroxysmal syndrome is typical not only for a stroke, but also for various brain damages (mass lesions, etc.). Due to its high diagnostic significance, it is recommended by the American Epilepsy Society as a mandatory indication for brain MRI [122].

The emergence of convulsions at the onset of a cerebrovascular pathology is a relatively unfavorable sign. It is proved that it is specifically the ACVD manifestation in paroxysms recurring soon, that is associated with the unfavorable prognosis regarding the patient rehabilitation and the restoration of the focal neurologic deficiency as well as with the risk of emergence and severe course of symptomatic epilepsy [99; 125; 259]. Normally, convulsions are not the only manifestation of an ACVD. A focal neurologic deficiency develops either alongside with them, or in the later periods [35; 220; 280]. The largest samplings of patients with an ACVD and formation of a post-stroke epilepsy during the subsequent period of the disease are presented in Table 1.

Table 1: Epilepsy formation risk in children, who had suffered an ischemic stroke (according to literature data from 2010 till 2015)

On the other hand, the first manifestations of the disease may be rather non-specific: an isolated degradation of consciousness level or a headache, which, considering age, difficulties in awareness and in verbalization of unusual symptoms by the child itself as well as lack of «stroke» alertness in pediatric neurologists, leads to an essential delay in neuroimaging and ACVD diagnosing [24; 60; 63; 67; 179]. These circumstances often lead to a rather paradoxical situation called «clinicodiagnostic scissors»: children with CVD symptoms are hospitalized promptly enough, but they do not get adequate verification of the diagnosis, including an instrumental one, and, therefore, they do not get the treatment.