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PSYB65H3 (479)
Ted Petit (185)
Chapter 14

PSYB65 Chapter 14.docx

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Ted Petit

Chapter 14: Human Brain Damage  Causes of Brain Damage Tumours • Mass of new and abnormal tissue that is not physiologically beneficial to its surrounding structures • Space-occupying lesions – foreign objects that cause damage to the CNS by putting pressure on it and occupying space that is normally occupied by the CNS • Brain is common site for tumour growth, second to the uterus • Tumours differ from one another in terms of what type of cell gives rise to the tumour, how rapidly they grow, whether they infiltrate and destroy the surrounding neural tissue or remain relatively encapsulated, and how likely they are to recur if they are removed • Benign tumours not likely to recur, malignant ones are more likely to recur Tumours Arising from Glial Cells • Most common are gliomas o Astrocytomas – tumours that arise from growth of astrocytes  Tend not to grow very quickly, rarely malignant  Damage from compression of surrounding tissues  Other astrocytomas infiltrate the surrounding neural tissue  When surgical treatment is not practical, chemotherapy is typically used o Glioblastoma  Opposite of astrocytomas  Grow quickly, highly malignant  Infiltrate the surrounding tissues making it difficult to excise surgically without removing relatively healthy surrounding neural tissue  Chemotherapy is often used o Medulloblastoma  Less common type  Highly malignant infiltrating tumour  Location and nature of these tumours makes chemotherapy popular Tumours Arising from the Meninges • Meningiomas are tumours that grow out of the meninges o Harmful effects of these tumours tend to result from pressure applied at the site of the tumour as well as sites distal from the tumour o Most are relatively benign o Surgery is best treatment because of their encapsulated nature and location Metastatic Tumours • Secondary tumours that form from migrated tumour tissue • Primary tumour site can be in lungs, breasts, uterus, or kidneys • More common for original tumour to be located outside CNS • Simple metastatic tumours occur when only one tumour forms at one site o Surgical or radiological treatment quite effective • Multiple metastatic tumours o Spreading from lungs to CNS o Whole-brain radiotherapy or chemotherapy  Prognosis quite poor Neuropsychological Effects of Tumours • Pressure placed on optic chiasm from pituitary tumours can also result in visual field defects o Due to proximity • More rapidly growing meningioma that is well encapsulated between two hemispheres could apply pressure to the primary motor and sensory cortices in this region, causing numbness and paresis to the feet and legs • Metastatic tumours form in the left temporal lobe can cause speech disturbances • Tumours in the left parietal lobe can lead to apraxia • Tumours can also release toxins and toxins can be transported from the site of origin producing lesions and behavioural deficits Cerebrovascular Disorders • Occurs when the blood supply to the brain is interrupted o Can be sudden or gradual, complete or relative, permanent or transient • Leading cause of disabling neurological damage and third most common cause of death in developed world (Cancer is leading cause, followed by heart attack) • Cerebrovascular accident (CVA) o Term for stroke o Interruptions to brain’s blood supply o Can be quite sudden or can get gradually worse o Results in cerebral ischemia  Lack of blood supply to the brain  If severe or long-lasting enough to kill neurons, damaged area is called infarct • Caused by blocked cerebral arteries, broken cerebral arteries, or interruptions of blood supply outside CNS • Thrombosis – blood clot forms within a cerebral blood vessel o Can form outside of the brain o Most common cause is atherosclerosis  Fatty deposits build up inside the walls of blood vessels, constricting the vessel more and more and possibly even completely blocking it o Symptoms appear gradually o Forms where two relatively large arteries branch off from one single artery called bifurcation  Constriction of blood flow tends to influence relatively large areas of the brain • Embolism o Similar form to a thrombosis o Involve the blocking of an artery by the build-up of a substance o Normally a clot that travels in the bloodstream from one part of the body to another o Travels from a spot where the arteries are relatively large to a place where the arteries are smaller than the point of original formation o Obstruction of blood flow is often quite sudden and complete o Can be treated surgically depending on where they form, or use anticoagulant drugs • Hemorrhage o Interruption in blood supply to the brain can be caused by the breakage of a blood vessel o Due to presence of a thrombosis or embolism, artery can be malformed, having weak spot called aneurysm o Or abnormally high blood pressure, hypertension, piercing of a blood vessel by a foreign or displaced object o Supply of oxygen and glucose disrupted, and blood is somewhat toxic to the neural tissue o Pressure can result in the displacement of neural centers that are critical for basic vegetative functions o When hemorrhage occurs within the brain, called intracerebral hemorrhage  Bleeds caused by hypertension, and damage that the bleeding produces is a result of the interruption of blood flow, toxicity of the uncontained blood, and pressure build-up at and away from the site of the bleed  Unlikely to recur, but prognosis is quite poor o Subarachnoid hemorrhage  Bleeding into the subarachnoid space  Result of hypertension but threat is from pressure exerted by the bleed  Symptoms are sudden • Severe headache, nausea, loss of consciousness  Don’t recur, prognosis is poor • Congenital defects present at birth, others caused by physical trauma o Arteriovenus malformation (AVM)  Malformed arteries and vessels that have extra or missing connections, resulting in abnormal blood flow  Some bleed at some/many points in individual’s life, but many exist without incident throughout otherwise healthy life  Bleed very small amounts over long periods of time, and bleed more than once  Damage result from a lack or irrigation of a particular area coupled with the toxicity of the blood itself o Aneurysm  Area of the artery that dilates because of local weakness  Some present very early in life, others appear later in result of trauma  Some bleed or even burst, others appear never to produce a noticeable problem  If starts to bleed slowly and this bleed is detected, prognosis can be quite good • Especially if accessible for surgery  If aneurysm suddenly bursts, rupture is often fatal • Very rare  Use surgery, drugs, or draining procedures • Drugs could start an uncontrollable
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