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Chapter 14

Chapter 14 Notes

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University of Toronto Scarborough
Ted Petit

Human Brain & Behaviour Chapter 14 CAUSES OF BRAIN DAMAGE TUMORS Atumor is a mass of new & abnormal tissue that is not physiologically beneficial to its surrounding structures Also called neoplasms new tissue Space-occupying lesions: they are foreign objects that cause damage to the CNS by putting pressure on it & occupying space that is normally occupied by the CNS. Different types of tumors damage is not only caused by exerting pressure. Tumors differ in terms of what type of cell gives rise to the tumor, how rapidly they grow, whether they infiltrate and destroy surrounding neural tissue or remail relatively encapsulated, and how likely they are to recur if they are removed. Benign tumors: not likely to recur Malignant: more likely to recur 4 major types of brain tumors: originating from a) glial cells b) the meninges c) nervous tissue d) other parts of the body already infected with a tumor TumorsArising From Glial Cells Gliomas = Most common type of tumors 2 main types of gliomas Astrocytomas: tumors that arise from the growth of astrocytes. Tend to grow slowly and usually benign. Some are well encapsulated, so the damage that they cause tends to come from compression of the surrounding tissues. Other astrocytes infiltrate surrounding neural tissue. If tumor started to grow in a relatively accessible location, surgery can correct proble. Even if benign, very dangerous if location is inaccessible. Options: Surgery or chemotherapy. Glioblastoma: Opposite of astrocytomas grow quickly, highly malignant, are not encapsulated, they infiltrate surrounding tissue making it hard to spare surrounding tissue while removing tumor. Treatment: Chemotherapy. Medulloblastoma: Less common (2-6% of all glicomas) highly malignant infiltrating tumor. Tend to form around cerebellum and brainstem early in life. Because of the location and nature of these tumors, chemotherapy is usually the best treatment option, however prognosis for these individuals is quite poor since brainstem and cerebellum are responsible for basic survival functions. TumorsArising From The Meninges Meningiomas: Tumors that grow out of (and remain attached to) the meninges. Most of them grow out of the dura mater, forming an ovoid shape. Tend to be well encapsulated since they grow out of tissues found outside the CNS. Harmful effects are therefore due to exerted pressure. Most are relatively benign but there are also some malignant varieties. Treatment: Surgery due to accessible location. Metastatic Tumors Mestatic Tumors: Secondary tumors that form from migrated tumor tissue. Primary site can be located in parts of the body such as the lungs, breasts, uterus, or kidneys. Most commonly, original site of tumor is outside of the CNS. Simple metastatic tumors: occur when only one tumor forms at one site. Treated with surgical or radiological treatment quite effective. Multiple metastatic tumors: More common; usually spreading from the lungs to the CNS. Treatment of chemotherapy or whole-brain radiotherapy but prognosis is quite poor. Neuropsychological Effects of Tumors Behavioural symptoms vary Slow-growing infiltrating astrocytoma near primary visual cortex = gradual blindness in parts of a visual field Tumors in pituitary gland can have similar effects to those of a visual cortex tumor Rapidly growing meningioma numbness & paresis to the feet and legs. Mestatic tumors in the left temporal love speech disturbances, receptive language problems Tumors in left parietal lobe apraxia Tumors can also cause epileptic seizures and release substances that are toxic to the brain If tumor is located in ventricles and releases toxins can easily cause defects not confined to a specific region within which it originates. CEREBROVASCULAR DISORDERS Occurs when the blood supply to the brain is interrupted; interruption can be sudden or gradual, complete or relative, permanent or transient. They are the leading cause of disabling neurological damage and the 3 most common cause of death in the developed world. Cerebrovascular Accident = A.k.a = Stroke Stroke = Cerebrovascular Accident (CVA) = a class of cerebrovascular disorders, all of which result in interruptions to the brain's blood supply. CVAresults in cerebral ischemia Alack of blood supply to the brain. If severe, or long-lasting enough to kill neurons, the damaged area is called an infarct. Infarcts can be very small if CVAis restricted to small, minor arteries. Large if CVAis in a major vessel. Interruptions in blood supply can be caused by many things blocked cerebral arteries, broken cerebral arteries, or interruptions of blood supply outside of the CNS. Thrombosis If a blood clot forms within a cerebral blood vessel. Can also form outside of the brain If it forms in the heart, it can cause a heart attack Cause: atheroscleosis: fatty deposits build up inside the walls of blood vessels, constricting the vessel more and more and possibly even completely blocking it. Buildup of fatty deposits = gradual = the symptoms appear gradually Constriction of blood flow tends to influence relatively large areas of the brain, and the neuropsychological symptoms that result from the disorder are usually diffuse and gradual in nature Embolism Similar in form to a thrombosis = both involve the blocking of an artery by the buildup of a substance. However, while thrombosis remains at point of origin, embolism is normally a clot that travels in the bloodstream from 1 part of the body to another. Typically, substance travels from a spot where arteries are relatively large to a place where the arteries are smaller than the point of original formation, so even though it may not have blocked before, it may now block the smaller arteries. Embolisms can be extremely dangerous if the blockage is not relieved immediately. Prognosis: Can be treated surgically depending on where they form Also treated with anticoagulant drugs. Hemorrhage Breakage of a blood vessel Causes: Presence of a thrombosis or embolism can cause blood pressure to build to a point that the walls of the artery cannot sustain Artery itself - malformed, having a weak spot called an aneurysm. Abnormally high blood pressure, hypertension, and the piercing of a blood vessel by a foreign or displaced object, such a bullet. Damage: Interruption in blood supply Supply of oxygen and glucose is disrupted Blood itself is somewhat toxic to the neural tissue. Bleeding = pressure = compression injuries in other areas = displacement of neural centers associated with vegetative functions = medulla Intracerebral Hemorrhage Hemorrhage occurs within the brain Causes: Bleeds are usually caused by hypertension Damage due to interruption of blood flow, toxicity of the uncontained blood, & pressure buildup at & away from the site of the bleed. Usually unlikely to recur Prognosis: Quite Poor Subarachno
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