The presence of familial cases of syringomyelia, basilar impression (intussusception) and Chiari malformation (MC) indicates the role of heredity in the occurrence of these diseases. Studies by a number of authors [32, 44] show that the primary pathology in this case is bone anomalies of the craniovertebral region (CVR), which contribute to the formation of the posterior cranial fossa (PCF) of reduced volume. As a result of this, the caudal parts of the cerebellum and the medulla oblongata descend through the foramen magnum (foramen magnum), i.e. formation of type I MC. In the presence of bone anomalies of KVO and MV type I, in some cases, a violation of CSF dynamics can occur at the level of the BVO, which will lead to the development and progression of syringomyelia. CVD abnormalities are, in turn, the result of defective development of the cartilaginous tissue of the bones of the skull and adjacent parts of the spine during the first weeks of embryonic development [34, 43]. Such dysembryogenesis may be due to dysfunction of genes that control the formation of the fifth occipital somite in the human body [49]. Literature data on familial cases of syringomyelia, basilar impression and MC confirm their common heredity basis.
The special features of the cerebral hemodynamics were studied in 138 patients with Chiari I malformation (CM) with a help of magnetic resonance angiography (MRA) and transcranial dopplerography (TCD). MRA data analysis (58) revealed the frequent presence of vertebrobasilar system (VBS) maldevelopment and embryonic type of the circle of Willis. TCD data analysis (100) discovered vertebrobasilar insufficiency and bilateral blood flow increase in the intracranial part of the internal carotid arteries giving evidence of the compensated blood flow from the carotid system to the VBS. 21,0% of patients with CM and communicating hydrocephalia had TCD signs of intracranial hypertension. The most significant changes in cerebral hemodynamics were found in patients with marked pathology and elder than 30 years old.
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