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Lecture 20

PSYC 211 Lecture 20: Chapter 14 Neurological disorders

21 Pages

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PSYC 211
Jonathan Britt

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PSYC 211 Chapter 14 Major categories of the neuropathological conditions that the brain can sustain: 1. Tumors 2. Seizure Disorders 3. Cerebrovascular accidents 4. Disorders of Development 5. Degenerative Disorders 6. Disorders caused by infectious disease Tumors A tumor is a mass of cells whose growth is uncontrolled and that serves no useful function Some are malignant - cancerous o Lacks a distinct border and may metastasize Others are benign - harmless/non-cancerous o Has a distinct border and cannot metastasize The major distinction between malignancy and benignancy is whether the tumor is encapsulated - whether there is a distinct border between the mass of tumor cells and the surrounding tissue o If the border exists, tumor is benign; surgeon can cut it out and it will not regrow o If the tumor grows by infiltrating the surrounding tissue, there will be no clear-cut border between the tumor and the normal tissue If the surgeon removes the tumor, some cells may be missed and those cells will produce a new tumor Malignant tumors often give rise to metastases - the process by which cells break off of a tumor, travel through the vascular system (bloodstream), lodge in capillaries, and grow new tumors in other locations in the body Tumors damage brain tissue by 2 means: o Compression and infiltration o Any tumor in the brain (malignant or benign) can produce neurological symptoms and threaten patient's life Even a benign tumors occupies space and thus pushes against the brain Compression can directly destroy brain tissue, or do so indirectly by blocking the flow of cerebrospinal fluid and causing hydrocephalus o Malignant tumors cause both compression and infiltration As it grows, it invades the surrounding region and destroys cells in the way Tumors arise from other cells found in the brain or from metastases originating elsewhere in the body - not from neurons (mature neurons are not capable of division) The most serious types of tumors are metastases and gliomas - derived from various glial cells o Gliomas are usually very malignant and fast growing o Malignancy of brain tumors are caused by rare subpopulation of cells o Malignant gliomas contain tumor-initiating cells - cells that originate from transformations of neural stem cells, rapidly proliferate, and give rise to a glioma o Gliomas are more resistant to chemotherapy and radiation than most tumor cells, so the survival rate from these tumors is low Meningioma - an encapsulated, benign tumor consisting of cells that constitute the dura mater or arachnoid membrane o Composed of cells that constitute the meninges PSYC 211 o Originate in the part of the dura mater that is found between the two cerebral hemispheres, or along the tentorium - sheet of dura mater lying between the occipital lobe and cerebellum o Case - woman (Mrs. R) whose sudden onset of seizures suggested the presence of a tumor near the top of the primary motor cortex (meningioma) Early symptoms were seizures localized in her foot (foot would shake) Then seizure spread through her lower leg, and then her upper leg, whole body - convulsions became more and more violent Lost consciousness Types of Brain Tumors: Gliomas Glioblastoma multiforme (poorly differentiated glial cells) Astrocytoma (astrocytes) Ependymoma (ependymal cells that line ventricles) Medulloblastoma (cells in roof of fourth ventricle) Oligodendrocytoma (oligodendrocytes) Meningioma (cells of the meninges) Pituitary adenoma (hormone-secreting cells of the pituitary gland) Neurinoma (Schwann cells or cells of connective tissue covering cranial nerves) Metastatic carcinoma (depends on the nature of the primary tumor) Angioma (cells of blood vessels) Pinealoma (cells of pineal gland) Seizure Disorders Seizure disorder - preferred term for epilepsy o Has many causes o 2nd most important category of neurological disorders - following stroke Seizure is a period of sudden, excessive activity (excitability) of cerebral neurons If neurons that make up the motor system are involved, seizures can cause a convulsion - wild, uncontrollable activity of the muscles o But most seizures don't cause convulsions Seizures have physical causes 2 distinctions of seizures: o Partial vs generalized and simple vs. complex Partial seizures - begins at a focus and remains localized; doesn't generalize to the rest of the brain o Typically caused by a scarred region (caused by an old injury) or a developmental abnormality (i.e. malformed blood vessel) o Neurons involved in the seizure are restricted to a small part of the brain o Symptoms can include sensory changes, motor activity (or both) o Divided into 2 categories: Simple seizures - do not cause loss in consciousness, but may cause changes in consciousness; starts from focus point and remains localized Ex: if it begins in or near the motor cortex then it can involve jerking movements Mrs. R first seizure spell was a simply seizure The excitation in the brain spread along the precentral gyrus Seizure was triggered by an meningioma - tumor was pressing against the "foot" region of the left primary motor cortex Her second seizure spell was a complex seizure - she lost consciousness PSYC 211 Seizure localized in the occipital lobe may produce visual symptoms (temporary blindness, spots of colour, flashes of light) One in the parietal lobe can evoke somatosensations (temp. changes, feelings of pins and needles) Complex seizures - leads to loss in consciousness; starts from focus point and remains localized Generalized seizures - widespread, involving most of the brain o Typically grow from a focus, but sometimes their origin is not discovered Tonic-clonic seizure (grand mal seizure) - a generalized convulsive seizure (includes neurons in the motor systems) o Most severe form of seizure o Often before having this kind of seizure, a person experiences warning symptoms (i.e. changes in mood or sudden jerks of muscular activity) - the aura Aura - sensation that precedes a seizure; it's nature depends on the location of the seizure focus Ex: structures in the temporal lobe are involved in control of emotions, so seizures originating in that lobe will often begin with a change in emotional state or mood Could also cause hallucinations that include old memories Presumable caused by excitation of neurons surrounding the seizure focus o Beginning of tonic-clonic seizure is the tonic phase (1st phase) All the patient's skeletal muscles contract fully On some cases in can result in fracturing of the bones and the inability to breathe o Second phase is the clonic phase Patient shows rhythmic jerking movements (convulsions) Intense activity in the autonomic system (sweating and salivation) Loss of consciousness After this phase the patient is usually exhausted and needs to sleep for long periods of time Children are especially susceptible to seizure disorders o Most don't have tonic-clonic seizures, but have very brief seizures - spells of absence o Absence seizure (petite mal) - characterized by periods of inattention; staring off into the distance (and are not remembered) Repeated eye blinks Generalized seizure disorder During this time they are unresponsive and do not notice their attacks Can occur up to several hundred times a day Can disrupt a child's school performance as a result No long term consequences Seizures can cause brain damage o Approx. 50% of patient's with seizure disorders show evidence of damage to the hippocampus Hippocampal damage can be caused by a single episode of status epilepticus - a condition in which the patient undergoes a series of seizures without regaining consciousness Damage is caused by an excessive release of glutamate during the seizure o Amount of damage is correlated with the number and severity of seizures Seizures have many causes: PSYC 211 o Scarring (most common) - could be produced by an injury, a stroke, or developmental abnormality in the brain (or from a growing tumor) In the case of injuries, development of seizures can take a long time o High fever (caused by drugs or infections) Most common in children - 3% of children under age 5 sustain seizures associated with fevers Seizures are see
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