Hemisphere, cerebellum

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. 

The central nervous system consists of the brain and spinal cord. The average adult brain weighs 1250-1380 grams. The brain is divided into three gross parts the brainstem, the cerebrum, and the cerebellum. Structurally, the brain may be likened to a bouquet of flowers with the cerebrum (as two cerebral hemispheres) blossoming outwards above the brainstem the cerebellum is attached at the back of the brainstem. 

Figure 4.4 General structure of the brain the central nervous system consists of the spinal cord and the brain. The brain consists of the brain stem (medulla oblongata, cerebellum, pons, mesencephalon, diencephalon) and the cerebrum (cerebral hemispheres, subcortical white matter, basal ganglia).

The cerebellum lies posterior to the brainstem and is separated from it by the fourth ventricle. Anatomically it is divided into two hemispheres, each consisting of three lobes (anterior, posterior, and flocculonodular). The function of the cerebellum is to help plan and coordinate motor activity and to assume responsibility for comparing the actual movement with the intended motor pattern. The cerebellum interprets various sensory input and helps modulate motor output so that the actual movement closely resembles the intended motor program. The cerebellum is also concerned with the vestibular mechanisms responsible for maintaining balance and posture. Therapeutic medications are not usually targeted directly for the cerebellum, but incoordination and other movement disorders may result if a drug exerts a toxic side effect on the cerebellum. 

The dense intermingling of nerve fibers within the WM connects different regions of the brain with each other. Projectional fibers connect cerebral cortex and subcortical structures as well as cerebellum commissural fibers connect homologous areas between the two hemispheres of brain, and the association fibers connect various regions within the same cerebral hemisphere. The major function of the cerebral WM is simply to interconnect various regions of brain and transmit signals in-between them. 

Fig. 7. Anatomical organization of dopamine Di mRNA expression in the adult human brain (whole hemisphere horizontal images) at a dorsal (A) and ventral (B) level. Notice strong cortical expression of this dopamine receptor subtype in addition to the intense expression levels in the striatum (CN, Pu and NAc). Adapted from Hurd et al. (2001). aCg, anterior cingulate Amy, amygdala Cb, cerebellum cc, corpus callosum CN, caudate nucleus Cun, cuneus F, frontal lobe Hip, hippocampus hyp, hypothalamus I, insular cortex mPFC, medial prefrontal cortex mm, medial mammillary nucleus NAc, nucleus accumbens O, occipital lobe Phg, parahippocampal gyrus Pu, putamen SN, substantia nigra T, temporal lobe U, uncal gyrus.

The basilar artery ascends ventral to the pons to the ponto-midbrain junction in the interpeduncular cistern, where it divides into the two posterior cerebral arteries. Numerous small branches penetrate the brainstem and cerebellum. The basilar artery also gives rise to the anterior inferior cerebellar artery, which supplies the rostral cerebellum, brainstem, inner ear, and the superior cerebellar artery, which supplies the brainstem, superior half of the cerebellar hemisphere, vermis and dentate nucleus. 

Acute or chronic cerebral injury may cause effects in remote areas of brain (Meyer et at 1993), so-called diaschisis, by reducing neuronal inputs and metabolic activity in the contralateral cerebellum and ipsilateral internal capsule, thalamus and basal ganglia after cortical lesions in the ipsilateral cortex following internal capsule and thalamic lesions and in the contralateral hemisphere. The functional consequences of diaschisis are not clear (Bowler et at 1995). 

Remove and discard both cerebellum and brain stem, then separate the hemispheres and transfer them to a large petridish with ice-cold PBS. 

This chapter correlates emotions and attachment behavior in autism with the disturbed neuroanatomy found in the brains of these individuals. Neuropathological postmortem studies have consistently found abnormalities in the limbic system and the cerebellum of autistic individuals. Abnormal limbic structures include the amygdala, hippocampus, septal nucleus, and anterior cingulate cortex. In the cerebellum, abnormalities have been found in the cerebellar hemispheres and in the fastigial, emboliform, and globose nuclei. 

Tyrosine hydroxylase, the synthesizing enzyme of dopamine, is expressed by Purkinje cells of the ventral vermis (lobules I and X) and the hemisphere (ansiform lobule, parafiocculus) of rat cerebellum (Takada et al., 1993). Expression of tyrosine hydroxylase by Purkinje cells is increased in the mutant tottering and leaner mice (Austin et al., 1992). 

IX of the caudal vermis and low activity in the hemisphere, was described by Mufson et al. (1991) for primates and man. The administration of colchicine results in the expression of NGF-R in most cerebellar Purkinje cells (Pioro and Cuello, 1988, 1990 Pioro et al, 1991). Koh et al. (1989) and Fusco et al. (1991) found NGF-R mRNA expression and NGF-R immunoreactivity in adult rats to be present in alternating Purkinje cell zones of strong and weak activity (Fig. 38C,D). This zonal pattern was also observed by Pioro and Cuello (1990). Its correspondence to the pattern of mabQ113 (Zebrin) immunoreactive zones (Hawkes and Leclerc, 1987) was noticed by Sotelo and Wassef (1991) and verified by Dusart et al. (1994) in adult rats. Lesions of the white matter, or knife cuts isolating the dorsal portion of the vermis of the rat cerebellum induces NGF-R immunoreactivity in previously unstained Purkinje cells (Martinez-Murillo et al., 1993 Dusart et al., 1994). 

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