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Symptoms of white matter damage in the hemispheres
Last reviewed: 19.10.2021
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On a horizontal section of the brain - the so-called Flexigu section - one can see a white subcortical substance (centrum semioval) with a radial crown and an inner capsule. In the white matter of brain tissue, there are numerous conductors connecting the cerebral cortex with the underlying parts of the central nervous system.
The inner capsule (capsula interna) is a layer of white matter between the lenticular nucleus, on the one hand, and the head of the caudate nucleus with the thalamus, on the other. In the inner capsule, the front and back legs and knee are distinguished. The anterior stem is made up of axons of cells, mainly the frontal lobe, reaching the nuclei of the bridge of the brain and to the cerebellum (frontal-bridge cough path). When they turn off, there are disorders of coordination of movements and body postures, the patient can not stand and walk (astasia-abasia) - frontal ataxia. The anterior two-thirds of the posterior stem of the inner capsule are formed by a pyramidal tract, the cortical-nuclear path passes through the knee. The destruction of these conductors leads to central paralysis of the opposite limbs of the lower mimic muscles and half of the tongue (hemiplegia).
The posterior third of the posterior stem of the inner capsule consists of axons of thalamus cells that conduct impulses of all kinds of sensitivity to the cerebral cortex and subcortical formations. When these conductors are turned off, sensitivity is lost in the opposite half of the body (hemianesthesia). To these syndromes, hemianopsia can sometimes also join, due to the destruction of visual radiance adjacent to the posterior sections of the inner capsule.
With capsular hemiplegia (or hemiparesis), there are all signs of damage to the central motor neuron: spasticity of the musculature, increased deep reflexes, disappearance of surface reflexes (abdominal, etc.), the appearance of stop and wrist pathological reflexes, pathological syncopeies and protective reflexes. Very characteristic is the posture of Wernicke-Mann: the upper limb is bent in all joints and brought to the trunk; the lower limb is straightened and, when walking, produces circumambulatory (outlining) movements. There are several explanations for the emergence of this characteristic posture. The emergence of spasticity of flexor muscles on the upper limbs and extensors on the lower limbs is caused by an increase in the tone of the antigravitational musculature, the reduction of which is aimed at overcoming gravity. This automatic regulation is performed by reflexes of the brain stem (especially the vestibular systems), and such reflex arches are disinhibited when the inner capsule is damaged.
The described typical symptoms of capsular motor disorders are somewhat different in the acute period of the disease (especially in the early days of cerebral stroke). Muscle tone and deep reflexes are not elevated, but, conversely, are reduced. It is used in diagnosis to detect hemiplegia in patients who are in a coma or deep co-morbid state. If the upper limbs in the elbow joints are bent at the elbows on the back of the patient and simultaneously lowered, the forearm on the hemiplegia side first (due to the lower muscle tone) will drop first. For the same reason, on the side of paralysis, the lower limb is more rotated outwards.
Capsular hemianesthesia concerns all types of skin and deep sensitivity; while in contrast to the localization in the cortex, the sensitivity disorder captures the entire half of the body, since the conductors in the inner capsule are compact.
The hemianopia in the defeat of the very posterior parts of the inner capsule of the onset of visual radiance differs from the cortical preservation of the hemiophic reaction of the pupils to light. In this case, central fields of vision may fall out, which is not observed when the cortex of the occipital fields (the projection zone of the visual analyzer) is damaged.
In the lesions of the supracapsular zone, the semi-oval center, a similar pattern of disorders may appear, but often a non-apparent pattern of "three gemi" is observed, and motor disorders (with lesions of the foreground) or sensitive and visual lesions of the middle and posterior parts of the semi-ovoid center predominate.