Variations and abnormalities of the brain
Last reviewed: 19.10.2021
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Spinal cord. The spinal cord sometimes lacks the crosshairs of the pyramids. In 10% of cases on both sides and in 14% on one side there are no anterior cortico-spinal pathways. The number of segments of the spinal cord varies between 30-32 due to a decrease or increase in the lumbar and sacral segments. The central canal of the spinal cord may in some places be infected, the size of the terminal ventricle (Krause) varies considerably. Occasionally, some of the anterior and posterior roots of the spinal nerves, which are part of the "cauda equina," are connected to neighboring roots. The spinal nodes of the 5th pair of sacral nerves are often in a bag formed by the dura mater, and not outside it. The nodes of the sacral spinal nerves are often significantly shifted upwards.
Brain. Numerous variations in the number, shape, and size of the fissures and crinkles of the cortex of the cerebral hemispheres are observed. In the frontal lobe there may be no upper frontal sulcus (1%), lower frontal (16%), precentral (6%). An intertrained sulcus is absent in 2% of cases, postcentral groove in 25%, lower temporal furrow in 43% of cases. Many furrows of the cortex of the cerebral hemispheres split. The lateral groove bifurcates in its posterior part in 40% of cases, divided into 3-4 parts in 6% of cases. The upper and lower frontal sulcus in 13% of cases are joined into one furrow. The supraorbital transverse furrow is sometimes defined on the lower surface of the frontal lobe. The postcentral groove sometimes merges with the intercostal sulcus, the posterior part of the lateral sulcus (in 31% of cases). In 56% of cases, the furrow of the same name parallel to the lumbar furrow passes through it. In 40% of cases there is an additional arc furrow of the ancestors. The superior occipital furrow is bifurcated (in 55% of cases) or tripled (in 12% of cases) in the form of two or three transverse furrows. The middle temporal groove is sometimes replaced by several radial or divergent furrows.
Sometimes in the olfactory tract there is a longitudinal canal. Rarely, between the area of divergence of the legs of the arch and the roller of the corpus callosum, there is a small flattened quadrangular and a closed slit (triangular slit). The base of this slot is facing anterior.
The size and shape of the thalamus are variable, rarely two intertalamic fusion. The sizes of mastoid bodies are also different. The configuration, the relationships of the hypothalamic nuclei, their dimensions are variable. The depth of the intercostal fossa, the number of holes in the rear perforated substance can be different. Variations in the extent and dimensions of the black matter and red nucleus are observed. The depth of the basilar groove of the bridge may be different. The shape of the bridge, the thickness of the middle legs of the cerebellum are individually variable. There is a one-sided or bilateral absence of brain strips, an oblique or lateral course on the surface of the medulla oblongata. The number of cerebellar gyrations is from 127 to 244. Lateral to the front surface of the lower part of the worm can be observed a small additional lobe - a pyramid. Additional pieces of the cerebellum fixed to the worm with independent pens are described.
There are other variations in the structure of different parts of the brain. The severe malformations of the brain are described: its absence (brain agenesis) or the greater part of it, a different decrease in its size to 600-700 g (microcephaly). Possible underdevelopment of individual parts of the cortex, corpus callosum, cerebellum. Various forms of underdevelopment of the anterior commissure of the brain, the intersection of the optic nerves, the visual tracts, the pineal body, and the nucleus of the cranial nerves are described.