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Four types of intracranial hemorrhage may result from trauma or cerebral vascular lesions erectile dysfunction medication cheap generic levitra professional 20 mg on line. Epidural (extradural) hemorrhage results from injuries to the meningeal arteries (commonly the anterior division of the middle meningeal artery) or veins. Arterial or venous injury is especially likely to occur if the vessels enter a bony canal in this region. Bleeding occurs and strips the meningeal layer of dura from the internal surface of the skull. Blood may also pass laterally through the fracture line to form a soft In severe cases, the baby may be unresponsive, the fonta- nelles are bulging, and the child may have retinal hemorrhages. Space-Occupying Lesions Within the Skull Space-occupying or expanding lesions within the skull include tumor, hematoma, and abscess. Because the skull is a rigid container of fixed volume, these lesions will add to the normal bulk of the intracranial contents. The position of the tumor within the brain may have a dramatic effect on the signs and symptoms. The signs and symptoms that enable the clinician to localize the lesion will depend on the degree of interference with brain function and nervous tissue destruction. Severe headache, possibly due to the stretching of the dura mater, and vomiting, due to pressure on the brainstem, are common complaints. A spinal tap should not be performed in patients with suspected intracranial tumor. The x-rays having passed through the head are collected by a special x-ray detector. The information is fed to a computer that processes the information, which is then displayed as a reconstructed picture on a screen. Essentially, the observer sees an image of a thin slice through the head, which may then be photographed for later examination. The sensitivity is such that small differences in x-ray absorption can be easily displayed. The gray matter of the cerebral cortex, white matter, internal capsule, corpus callosum, ventricles, and subarachnoid spaces can all be recognized. An iodine-containing medium can be injected intravascularly, which enhances greatly the contrast between tissues having a different blood flow. The excited hydrogen nuclei emit a signal that is detected as induced electric currents in a receiver coil. The reason for this is that gray matter contains more hydrogen in the form of water than white matter, and the hydrogen atoms are less bound in fat. The appropriate isotope is incorporated into molecules of known biochemical behavior in the brain and then is injected into the patient. Making a series of time-lapse images at different anatomical sites allows variations in brain metabolism to be studied at these sites. This technique has been used to study the distribution and activity of neurotransmitters, variations in oxygen utilization, and cerebral blood flow. A high concentration of the compound (circular yellow area) is seen in the region of the tumor. The spinal nerves divide into anterior and posterior rami, both containing motor and sensory fibers. Anterior rami supply the muscles and skin of the limbs and the anterolateral body wall. Major Divisions of the Central Nervous System 0 the brain has three major divisions: hindbrain, midbrain, and forebrain. The ectoderm gives rise to the entire nervous system, initially forming the neural plate, then neural folds, and subsequently fusing into the neural tube. The leading edge of the neural folds contains neural crest cells which differentiate into ganglion cells, Schwann cells, melanocytes, and cells of the suprarenal medulla. A 45-year-old woman is examined by her physician and found to have carcinoma of the thyroid gland. Apart from swelling in the neck, the patient also complains of back pain in the lower thoracic region, with a burning soreness radiating around the right side of her thorax over the 10th intercostal space. Although the back pain can be relieved by changing posture, it is worsened by coughing and sneezing. A lateral radiograph of the thoracic part of the vertebral column reveals a secondary carcinomatous deposit in the 10th thoracic vertebral body. Using your knowledge of neuroanatomy, explain the following: (a) the pain in the back, (b) the soreness over the right 10th intercostal space, (c) the muscular weakness of both legs, and (d) which segments of the spinal cord lie at the level of the 10th thoracic vertebral body. A 35-year-old coal miner is crouching down at the mine face to inspect a drilling machine. A large rock suddenly dislodges from the roof of the mine shaft and strikes the miner on the upper part of his back. What anatomical factors in the thoracic region determine the degree of injury that may occur to the spinal cord A 20-year-old man with a long history of tuberculosis of the lungs is examined by an orthopedic surgeon because of the sudden development of a humpback (kyphosis). He also has symptoms of a stabbing pain radiating around both sides of mebooksfree. A diagnosis of tuberculous osteitis of the 5th thoracic vertebra is made, with the collapse of the vertebral body responsible for the kyphosis. Using your knowledge of neuroanatomy, explain why the collapse of the 5th thoracic vertebral body should cause pain in the distribution of the 5th thoracic segmental nerve on both sides. A 50-year-old man wakes up one morning with a severe pain near the lower part of the back of his neck and left shoulder. Movement of the neck causes an increase in the intensity of the pain, which is also accentuated by coughing. A lateral radiograph of the neck shows a slight narrowing of the space between the 5th and 6th cervical vertebral bodies.
The involuntary tracking movement of the eyes when following moving objects is unaffected erectile dysfunction over the counter buy discount levitra professional 20 mg, because the lesion does not involve the visual cortex in the occipital lobe. Irritative lesions of the frontal eye field of one hemisphere cause the two eyes to periodically deviate to the opposite side of the lesion. Lesions of the primary motor cortex in one hemisphere result in paralysis of the contralateral extremities, with the finer and more skilled movements suffering most. Destruction of the primary motor area (area 4) produces more severe paralysis than destruction of the secondary motor area (area 6). Destruction of both areas produces the most complete form of contralateral paralysis. Lesions of the secondary motor area alone produce difficulty in the performance of skilled movements, with little loss of strength. The Jacksonian epileptic seizure is due to an irritative lesion of the primary motor area (area 4). The convulsion begins in the part of the body represented in the primary motor area that is being irritated. The convulsive movement may be restricted to one part of the body, such as the face or the foot, or it may spread to involve many regions, depending on the spread of irritation of the primary motor area. Destructive lesions in the left inferior frontal gyrus result in the loss of ability to produce speech, that is, expressive aphasia. The patients, however, retain the ability to think the words they wish to say, they can write the words, and they can understand their meaning when they see or hear them. Destructive lesions restricted to the Wernicke speech area in the dominant hemisphere produce a loss of ability to understand the spoken and written word, that is, receptive aphasia. Since the Broca area is unaffected, speech is unimpaired, and the patient can produce fluent speech. However, the patient is unaware of the meaning of the words he or she uses and uses incorrect words or even nonexistent words. Patients who have lesions involving the insula have difficulty in pronouncing phonemes in their proper order and usually produce sounds that are close to the target word but are not exactly correct. The patient remains unable to judge degrees of warmth, unable to localize tactile stimuli accurately, and unable to judge weights of objects. Lesions of the secondary somesthetic area of the cortex do not cause recognizable sensory defects. Destructive lesions in the angular gyrus in the posterior parietal lobe (often considered a part of the Wernicke area) divide the pathway between the visual association area and the anterior part of the Wernicke area. Destruction of the prefrontal region does not produce any marked loss of intelligence. It is an area of the cortex that is capable of associating experiences that are necessary for the production of abstract ideas, judgment, emotional feeling, and personality. The patient no longer conforms to the accepted mode of social behavior and becomes careless of dress and appearance. For example, with the eyes closed, the individual would be unable to recognize a key placed in the hand. Destruction of the posterior part of the parietal lobe, which integrates somatic and visual sensations, will interfere with the appreciation of body image on the opposite side of the body. The individual may fail to recognize the opposite side of the body as his or her own. The patient may fail to wash it or dress it or to shave that side of the face or legs. A failure of this innervation may be responsible for some of the symptoms of schizophrenia, which include important disorders of thought. Lesions involving the walls of the posterior part of one calcarine sulcus result in a loss of sight in the opposite visual field, that is, crossed homonymous hemianopia. Interestingly, the central part of the visual field is apparently normal when tested. Lesions of the upper half of one primary visual area-the area above the calcarine sulcus-result in inferior quadrantic hemianopia, whereas lesions involving one visual area below the calcarine sulcus result in superior quadrantic hemianopia. The most common causes of these lesions are vascular disorders, tumors, Frontal leukotomy (cutting the fiber tracts of the frontal lobe) and frontal lobectomy (removal of the frontal lobe) are surgical procedures that have been used to reduce the emotional responsiveness of patients with obsessive emotional states and intractable pain. The surgical technique was developed to remove the frontal association activity so that past experience is not recalled and the possibilities of the future are not considered; thus, introspection is and injuries from gunshot wounds. Lesions of the secondary visual area result in a loss of ability to recognize objects seen in the opposite field of vision. The reason for this is that the area of cortex that stores past visual experiences has been lost. A patient suffering severe pain, such as may be experienced in the terminal stages of cancer, will still feel the pain following frontal lobectomy, but he or she will no longer worry about the pain and, therefore, will not suffer. It should be pointed out that the introduction of effective tranquilizing and mood-elevating drugs has made these operative procedures largely obsolete. Because the primary auditory area in the inferior wall of the lateral sulcus receives nerve fibers from both cochleae, a lesion of one cortical area will produce slight bilateral loss of hearing, but the loss will be greater in the opposite ear. The lower centers of the brain, principally the thalamus, relay a large part of the sensory signals to the cerebral cortex for analysis. The sensory cortex is necessary for the appreciation of spatial recognition, recognition of relative Lesions of the cortex posterior to the primary auditory area in the lateral sulcus and in the superior temporal gyrus result in an inability to interpret sounds. Lesions of the primary somesthetic area of the cortex result in contralateral sensory disturbances, which are most severe in the distal parts of the limbs. Crude painful, Cerebral Dominance and Cerebral Damage Although both hemispheres are almost identical in structure, handedness, perception of language, speech, spatial mebooksfree. About 90% of people are right-handed, and the control resides in the left hemisphere.
The afferent mossy fibers may stimulate many Purkinje cells by first stimulating the granular cells erectile dysfunction non prescription drugs order levitra professional 20 mg otc. The neurons of the intracerebellar nuclei send axons to the ventrolateral nucleus of the thalamus, where they are relayed to the cerebral cortex. Past-pointing is caused by the failure of the cerebellum to inhibit the cerebral cortex after the movement has begun. The cerebellar cortex has the same uniform microscopic structure in different individuals. The axons of the Purkinje cells exert a stimulatory influence on the neurons of the deep cerebellar nuclei. Each cerebellar hemisphere principally influences movement on the same side of the body. Patients with cerebellar disease frequently exhibit poor muscle tone, and to compensate for this, they stand stiff legged with their feet wide apart. Although patients with cerebellar disease display disturbances of voluntary movement, none of the muscles are paralyzed or show atrophy. On close questioning, the patient admits that the headache is made worse by changing the position of his head. The aggravation of the headache caused by changing the position of the head can be explained by the fact that the cyst is mobile and suspended from the choroid plexus. When the head is moved into certain positions, the ball-like cyst blocks the foramen of l/ onro on the right side, further raising the intracerebral pressure and increasing the hydrocephalus. The weakness and numb- ness of the left leg are due to pressure on the right thalamus and the tracts in the right internal capsule, produced by the slowly expanding tumor. The cerebral hemispheres are developed from the telencephalon and form the largest part of the brain. Each hemisphere has a covering of gray matter, the cortex and internal masses of gray matter, the basal nuclei, and a lateral ventricle. The basic anatomical structure of this area is described so that the student can be prepared for the complexities associated with functional localization. It extends posteriorly to the point where the third ventricle becomes continuous with the cerebral aqueduct and anteriorly as far as the interventricular foramina. Thus, the diencephalon is a midline structure with symmetrical right and left halves. Obviously, these subdivisions of the brain are made for convenience, and from a functional point of view, nerve fibers freely cross the boundaries. Gross Features the inferior surface of the diencephalon is the only area exposed to the surface in the intact brain. It may be divided into two parts: the diencephalon, which forms the central core, and the telencephalon, anterior to posterior, the optic chiasma, with the optic tract on either side; the infundibulum, with the tuber which forms the cerebral hemispheres. The superior surface of the diencephalon is concealed by the fornix, which is a thick bundle of fibers that originates in the hippocampus of the temporal lobe and arches posteriorly over the thalamus. The actual superior wall of the diencephalon is formed by the roof of the third ventricle. This consists of a layer of ependyma, which is continuous with the rest of the ependymal lining of the third ventricle. It is covered superiorly by a vascular fold of pia mater, called the tela choroidea of the third ventricle. From the roof of the third ventricle, a pair of vascular processes, the ch0roid plexuses of the third ventricle, project downward from the midline into the cavity of the third ventricle. The lateral surface of the diencephalon is bounded by the internal capsule of white matter and consists of nerve fibers that connect the cerebral cortex with other parts of the brainstem and spinal cord. Because the diencephalon is divided into symmetrical halves by the slitlike third ventricle, it also has a medial surface. These two areas are separated from one another by a shallow sulcus, the hypothalamic sulcus. A bundle of nerve fibers, which are afferent fibers to the habenular nucleus, forms a ridge along the superior margin of the medial surface of the diencephalon and is called the stria medullaris thalami. The diencephalon can be divided into four major parts: (1) the thalamus, (2) the subthalamus, (3) the epithala- mus, and (4) the hypothalamus. Thalamus the thalamus is a large ovoid mass of gray matter that forms the major part of the diencephalon. It is a region of great functional importance and serves as a cell station to all the main sensory systems (except the olfactory pathway). The activities of the thalamus are closely related to that of the cerebral cortex and damage to the thalamus causes great loss of cerebral function. B: Diagram showing the position of the thalamus within the right cerebral hemisphere and the relative position of the thalamic nuclei to one another. The anterior end of the thalamus is narrow and rounded and forms the posterior boundary of the interventricular foramen. The lateral geniculate body forms a small elevation on the under aspect of the lateral portion of the pulvinar. The superior surface of the thalamus is covered medially by the tela choroidea and the forniX, and laterally, it is covered by ependyma and forms part of the floor of the lateral ventricle; the lateral part is partially hidden by the choroid plexus of the lateral ventricle. The medial surface of the thalamus forms the superior part of the lateral wall of the third ventricle and is usually connected to the opposite thalamus by a band of gray matter, the interthalamic connection (intertha- lamic adhesion). The lateral surface of the thalamus is separated from the lentiform nucleus by the very important band of white matter called the internal capsule.