The value of MR and new recording techniques in the diagnostics of demyelinating diseases in children

MR is a diagnostic test which, in a non-invasive way, provides anatomic and physiological information on the principle of the magnetic field without the use of ionizing radiation. Like a CT, MR is also founded on computer layering of images of tissues, but with much better contrast resolution, which makes greater sensitivity and specificity possible than in CT imaging in the detection of diseases of the white matter of the brain. Precisely for these reasons, MR is the leading method of choice, the Gold Standard in diseases of the white matter, both in children and in adults. With the rapid development of new MR sequences and recording techniques, perfusion and diffusion and MR spectroscopy (MRS), which is based on an assessment of the ratio of individual metabolites in the brain, its reliability is growing in the detection of pathological conditions of the white matter, which we differentiate on the basis of the intensity of the signal, the pattern and distributions of the lesions and from the manner of imbibing after the application of i.v. contrast. The leading MR sequences for diagnosis of diseases of the white matter are T2 and FLAIR on which they are presented by an extremely heightened intensity of signal and newer MRS techniques. Although primarily demyelinating diseases are very rare in children, it is important to know their clinical and radiological presentation for the sake of timely diagnosis and suitable therapy and therefore a better prognosis. Acquired demyelinating diseases in children, which cause the destruction of the normally created myelin, may be caused by infections such as MS or ADEM, infective agents (Lyme disease, PML; HIV) and toxic metabolic damage (chemotherapy, radiation). Inherited or dysmyelinating diseases which lead to disturbed production of myelin, are the result of metabolic disorders in the synthesis of enzymes involved in building normal myelin. The best known of these are: Canavan disease, metachromatic leukodystrophy, Krabbe’s and Alexander’s disease, Pelizaeous-Merzbacher disease and X-linked adrenoleukodystrophy. All these illnesses and conditions have a specific radiological presentation on MR, which makes it much easier to establish a diagnosis where the clinical signs are unclear. In older children the same recording protocols are used as in adults, since in most cases they are cases of demyelinating diseases, whereas in young children special recording techniques must be used as the child brain contains about 10% more water than the brain of a mature man. All this would not be possible without MR of the appropriate strength of magnetic field (minimum 1.5 T) and of course the appropriate cooperation between clinicians and radiologists in making decisions about the method of choice and establishing the final diagnosis.

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