Cerebral hemispheres development

Brain metastasis is the most common neurologic complication seen in patients with cancer. Approximately 170,000 patients develop brain metastases in the United States each year.20 Many malignancies are frequently associated with brain metastases (Table 96-7). While melanoma is the tumor type most likely to metastasize to the brain, brain metastases owing to lung and breast cancers are seen more often because they are among the most common cancers. In addition, brain metastasis may be diagnosed at the same time as the primary malignancy in around 20% of cases.22 Around 80% of brain metastases occur in the cerebral hemispheres, 15% in the cerebellum, and 5% in the brain stem. 

X-ALD is a disorder of peroxisomal P-oxidation of VLCFA and is estimated to occur in approximately 1 20,000 males. The first description of an affected patient was in 1910. This patient was a previously healthy boy who developed visual disturbances at the age of 6 years, followed by deterioration of his schoolwork, and then spastic gait. His older brother had died of a similar illness in childhood. The brain pathology in this child revealed diffuse loss of myelin in the cerebral hemispheres. Involvement of the adrenal gland was subsequently reported in later-identified patients,... 

Cognitive or visual field defects may have to be assumed in drowsy patients. Deviation of the eyes towards the affected hemisphere is common but recovers in a few days. A large hematoma may cause midUne shift, transtentorial herniation and coma within 24-hours (Fig. 9.3). By contrast, these changes take two or three days to evolve with large infarcts as cerebral edema develops. 

On MRI multiple periventricular and discrete cerebral hemisphere white-matter lesions (plaques measuring at least 3 mm in diameter) are seen as bright areas. The 10-year ONTT results showed that an MRI obtained at baseline (new optic neuritis attack) can predict the risk of a patient developing MS. Patients with at least one brain lesion on MRI at the time of the optic neuritis episode have a 56% risk of developing MS within 10 years, whereas those with no brain lesions have only a 22% risk. There appears to be no increased risk of developing MS with a higher number of baseline lesions. 

The most useful way to understand this massively complex structure is by reference to its growth during development. As the embryo develops, there are at first three primary brain regions the prosencephalon (forebrain) the mesencephalon (midbrain) and the rhombencephalon (hindbrain). Within a few weeks the forebrain and hindbrain each divide in two. The forebrain gives rise to the telencephalon and diencephalon while the hindbrain gives rise to the metencephalon and the myelencephalon. The telencephalon of the forebrain then develops into the cerebrum with its hugely expanded, characteristic, cerebral hemispheres which cover the top and side surfaces of the brain (Table 5.1). The surface of the cerebrum is made up of central nerve... 

Harrington KA, Schindler M, Humphrey PP, Emson PC (1995) Expression of messenger RNA for somatostatin receptor subtype 4 in adult rat brain. Neurosci Lett 188 17-20 Hartmann D, Fehr S, Meyerhof W, Richter D (1995) Distribution of somatostatin receptor subtype 1 mRNA in the developing cerebral hemispheres of the rat Dev Neurosci 17 246-525... 

Primary culture of brain cells offers an interesting tool to analyze in vitro the complex events occuring in development. In cultures of cells dissociated from cerebral hemispheres of 14 days old embryonic mice the number of receptors increased during 6 days, the period of neuronal proliferation [32]. The number and the Ka of nuclear T3 receptors in cultured neurons obtained from the cerebral hemispheres of 15-16 old rat embryos increased between 5 to 9 days of culture, indicating that the in vitro model adequately reflects the in vivo situation, and in addition confirming that the receptor increase is mainly occuring in neurons. In astrocytes the increase in receptor number is less marked and happens only after 21 days of culture [33]. 

A transient encephalopathy has been reported after the use of an iodinated contrast medium in a neurointerventional procedure with development of psychomotor agitation, disorientation, and progressive left faciobrachial hemiparesis 30 minutes after successful treatment of a right carotid-ophthalmic fusiform aneurysm [6 ]. A CT scan showed marked cortical enhancement and edema in the right cerebral hemisphere, thought to be due to contrast extravasation after disruption of the blood-brain barrier. Treatment with dexa-methasone and maimitol produced complete recovery. 

This is made up of the brain and spinal cord. The brain is a highly developed mass of nerve cells at the upper end of the spinal cord. The largest part of the brain is taken up by the two cerebral hemispheres. These receive sensory messages from various parts of the body and originate the nerve impulses which produce voluntary movements. The layers of grey tissue (known as the cerebral cortex) overlying the cerebral hemispheres are covered in folds. This tissue is concerned with the intellectual function of the individual. The various parts of the cortex of the brain are associated with specific activities. For example, there are centres concerned with speech, hearing, vision, skin sensation and muscle movement. 

In humans and other more developed animals, most nerve cells are located in the brain and in the spinal cord, which together make up the central nervous system. The brain acts to process and integrate information. It is composed of several parts, the thinking portion of which is composed of two hemispheres at the top and front of the brain, called the cerebrum. This part of the brain is covered with a thin layer of gray matter called the cerebral cortex. 

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