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44 Cards in this Set
- Front
- Back
MRI
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• Relatively new diagnostic procedure & has only been available for routine brain imaging since mid 1980s
• Completely safe & can't be felt • Only 1 inch of space around the head, placed approximately 4 feet around the center of the imager • Small confines of MRI are significant problem for patients who suffer from claustrophobia • For clinical diagnostic studies, the procedure takes about 15 minutes, during which the patient must remain as stationary as possible. • Loud clicks are bombardments of radio frequency on the brain, which has been placed under a high magnetic field. |
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Neuronistology techniques
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• One of the first ways to study neural processes involves stains chemicals that attach themselves to specific cell structures & thereby makes it possible for researchers to examine them visually & even count them
• Introduction of powerful electron microscope in 150s made it possible to analyze in detail the synaptic contact between individual neurons |
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Golgi Stain
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• Golgi, Italian physician discovered that silver chromate stained dead neurons black
• Gogli method has remained in use for more than 100 years to characterize specific cell types in different regions of nervous system |
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Nissl stain
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• One drawback of the Golgi stain is that it provides little information about the number of neurons in specific brain regions, because it only affects a few neurons.
• Using Nissl stain scientists could then count the number of Nissl-stained dots represent neurons in any area of the brain |
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Other staining techniques
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• Remains a viable method for studying cellular formation of nervous systems & helps neurosis in studying specialized contacts among neurons & their complex & often puzzling arrangements.
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Radiological Procedures
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• Rapid process of radiology has made a significant impact on field of clinical neurology & neuropsychology
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Skull X-ray
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• Wilhelm Conrad Rontgen produced an invisible ray that could pass through wood & other solid materials (unlike heat or light waves)
• Also called x-ray, gave rise to radiology • Diagnostic x-ray films are very useful for clinical work on various parts of body, because they reveal the presence & position of bones, fractures, & foreign bodies |
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Air Encephalography (Pneumoencephalography)
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• Radiographic visualization of fluid-containing structures of brain ventricles & spinal column
• An advance on standard x-ray because it allowed visualization of ventricular system • Today, modern CT scan replaced AE & traditional x-ray |
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Computed Transaxial Tomography Scan [CT]
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• Based on the same principle as an x-ray but scanned with a much narrower beam
• CT scan was invented in Britain in 1971 and brought to the US in 1972 • After placing patient’s head in the center of the scanner, technology revolves x-ray source around head as detectors monitor intensity of x-ray beam passed through the brain. |
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Progression of CT scan
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• Progressed from detecting gross feature to highly refined structural features
• Prior to new technology, precise neuropathological diagnosis was difficult & psychologists played a large role in diagnosing lesions, including stroke & tumors. |
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CT scan Procedure
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• Multi-transaxial images of brain are obtained from many different angles
• Information obtained by scanner entered into computer, which then calculates in 3D space, cross-sections brain within a plane of horizontal x-ray beam & available density information of brain. • From this data, the computer generates pictures of the brain that can be in any orientation • The final product of CT technology is to produce visualization of brain structures. |
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hyperdensity
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(typically signals abnormal density such as tumor or an internal bleed)
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hypodensity
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(associated with low density & perhaps an old lesion)
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CT scan continued
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• Neuroradiologists closely examine scans for abnormal densities both hypodensity & hyperdensity
• The enchanced CT scan, involves an IV injecting iodinated contrast agent which reveals more contrast in brain structure. |
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Angiography
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• Roentgenographic visualization (x-raying) of vessels in the brain after introducing contrast material into arterial or venous blood stream.
• The technique is based on x-ray, it examines the brain through the vascular system • It allows from the puncture of a signle artery the maximum radiographic for diagnosing intracerebral lesions • It is useful in diagnosing cerebrovascular disorders. |
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Sodium-Amytal Injections (Wada)
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• Named Wada for the developer
• It is similar to the angiogram in that the examiner places a catheter, typically in the left or right internal carotid artery • Barbiturate sodium amytal is injected which temporarily anesthetizes one hemisphere. • Neuropsychologists study precise functions of one hemisphere the other “sleeps” |
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Electroencegraphy (EEG)
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• recording of electrical activity of nerve cells of brain through electrodes attached to various locations on scalp
• One of the most widely used techniques in neurology • EEG is used to investigate distinct patterns of electric activity in normal & abnormal brain • Safe, painless & simple procedure |
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Hans Berger
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• Austrian psychiatrist who discovered that patterns of electrical activity can be recorded using metal electrodes placed on head.
• Discovered that electric activity of sleeping brain differed from awake brain • First dynamic way to measure brain function |
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EEG Recording
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• To record EEG technology places electrodes on scalp & connects them to EEG machine, which amplifies electrical potential of neurons recording activity immediately below the cortex
• Thus, EEG is mostly a measure of cortical nerve cells of the pyramidal type. |
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Brain Waves
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• In general, brain wave patterns are either rhythmic or arythmic (uneven)
• Typically, neurons fire in rhythmic/synchronous pattern leading to alpha, beta, delta, & theta waveforms. • Brain waves may differ in polarity, shape & frequency |
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EEG & Epilepsy
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• In epilepsy, neurons fire at once or in a burst or “spike”
• During seizures, cortical neurons participate in excitation • Behavior is disrupted & consciousness can be lost • Drugs that block gamma-amine-butryic acid (GABA) receptors increase possibility of seizure • Multiple seizures are typical of epilepsy • Epilepsy is often treated with anticonvulsant medications to reduce spiking |
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• Primary referral for clinical EEG is to help diagnose:
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o Seizure disorder
o Sleep disorder o Coma level o Brain dead? o Epilepsy |
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EEG Interpretation
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• Standard EEG typically has eight channels
• Interpreting EEG is an art because so many variables are introduced • Different EEG technicians often disagree on interpreting borderline abnormal EEGs although they easily diagnose more definite epileptic EEG patterns |
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BEAM
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• One invention that examines more dynamic aspects of electrophysiological brain activity is BEAM → Brain Electrical Activity Mapping
• BEAM is nothing more than a way to enhance information available on a standard EEG |
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BAER
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Brainstem Auditory Evoked Response
o Examiner presents clicks to each ear with headphones |
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Evoked Potential (EP)
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• Involves artificial stimulation of sensory fibers that generate electrical activity along central & peripheral pathways including primary receptive areas in brain
• Diagnostician analyzes EP amplitude latency, & location of brain region where stimulus is processed. |
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Electrical Stimulation
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• Historically, one of the oldest ways of brain investigation
• Negative responses (AKA disrupting of function) were discovered as result of Electrical Stimulation of cortex • Neurologists have been using Electrical Stimulation to treat Parkinson’s. |
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α Electromyography (EMG)
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the electrical analysis of muscles
o In EMG, diagnosticians perform a nerve conduction study of a specific muscle to diagnose neuromuscular disorders |
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α Imaging of Brain Metabolism
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o Such techniques are related to the biological fact that neurons have an active metabolism, which the cerebral blood supply provides
o Specifically, the delivery of oxygen & glucose to neurons depends on cerebral blood flow |
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α Regional Cerebral Blood Flow
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o Blood flow in the cerebral hemispheres varies with metabolism & activity
o The amount of blood flowing through different regions of the brain can indicate that region’s relative neural activity o Using this technique, researchers can study both hemispheres at the same time |
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α Single-Photon Emission Computed Tomography (SPECT)
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o A technique for the three-dimensional imaging of rCBF is single-photon emission computed tomography or SPECT.
o Using SPECT, it is possible to three-dimensionally image the distribution of a radioactively labeled contrast agent o Using this technique, analysts can estimate cerebral blood flow & blood volume |
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PET Research
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o demonstrates that the effects of cognitive effort on regional brain activity can be detected & measured
o Thus, studies using imaging technology indicate that there is a relationship between brain activity & behavior, & that PET can detect those associations o Are there really functional differences in the brain that arise from being male or female? o The most recent studies suggest there are |
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α Positron Emission Tomography (PET)
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o Emission tomography is a new visualization technique
o The method of PET technology is intravenous injection of a radioactive tracer (specifically positron-emitting substances) & subsequently scanning the brain for radioactivity o The major disadvantage of using PET clinically is the cost involved, principally related to the need for an expensive cyclotron |
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PET Measurement
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o The more active a specific area of the brain is, the more glucose it uses
o Thus, the resting brain differs metabolically from the active brain o Technicians administer radionuclides intravenously that the subject’s brain tissue takes up o Measuring glucose metabolism rate is a more direct measure of neuron function than is cerebral blood flow |
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α Magnetic Resonance Imaging (MRI)
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o Whereas CT uses penetrating x-ray radiation & PET uses radioactive isotopes, MRI is based on a fundamentally different process, namely, the fact that the hydrogen nucleus, which is present in high concentration in biologic systems, generates alternations in a small magnetic field, which can be measured
o MRI provides pictures of anatomy superior to CT particularly for diagnosing underlying pathologic disorders o MRI of the central nervous system has provided behavioral scientists & neuroradiologists with revolutionary quality of brain images in all planes (coronal, sagittal, & horizontal) o As a result, MRI has become a very important diagnostic tool for detecting disease processes |
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Reading an MRI
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o The principal technique involved in MRI is based on patterns similar to the pattern a magnet makes on surrounding metal flakes.
o The metal flakes align themselves according to the magnetic field o Because water is present in most biological tissue, this procedure can generate a strikingly accurate picture of the brain, or any other anatomy |
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fMRI
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o The advantage of fMRI over SPECT, PET, & CT is that there is no radiation exposure
o Therefore, fMRI is less invasive o However, scientists do not completely know the effects of exposure of the brain to high magnetic fields |
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α Magnetoencephalography (MEG)
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o involves measurement of changes in magnetic fields that are generated by underlying electrical activity of active neurons
o Neuronal activity generates not only electrical fields, but also magnetic fields o Meg is the magnetic equivalent of EEG o At this time MEG is experimental & is not used for routine clinical diagnostic studies |
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α Cerebrospinal Fluid Studies: Lumbar Puncture
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o The lumbar puncture or spinal tap is a medical technique to collect a sample of cerebrospinal fluid (CSF) surrounding the spinal cord for diagnostic study
o A long (3- to 3.5-inch) puncture needle is inserted perpendicular between the third & fourth (or fourth & fifth) lumbar vertebrae o At the end of the procedure, the physician withdraws the needle quickly o The lumbar puncture is relatively easy & routine way by which to obtain a CSF sample o Yet lumbar puncture is invasive & painful, requiring a local anesthetic, & infection is always a concern |
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CSF examination
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o On visual inspection, normal CSF is colorless & does not coagulate
o Technicians typically examine the CSF sample in a laboratory for cell count, glucose levels, & protein content, to detect CSF abnormalities o The lumbar puncture is a useful diagnostic aid for variety of neurologic conditions in which CSF has been “contaminated,” including acute & subacute bacterial meningitis, viral infections, brain abscess or tumor, multiple sclerosis, & hemorrhage |
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α Neurologic Exam
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o The neurologic exam is a routine introductory evaluation that a neurologist performs
o The neurologic exam involves a detailed history of the patient’s medical history & a careful assessment of the patient’s reflexes, cranial nerve functioning, gross movements, muscle tone, & ability to perceive sensory stimuli o The neurologic exam is not as detailed as a neuropsychological evaluation |
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α Neuropsychological Evaluation
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o Whereas neurologists are interested in changes in the nervous system that occur within the clinical context (such as lesions, disease, & trauma), neuropsychologists are primarily interested in higher cognitive functioning
o The neuropsychological evaluation provides additional information about the patient’s health, & is used, in conjunction with other pertinent information, for diagnosis, patient management, intervention, rehabilitation, & discharge planning o We strongly suggest that imaging technologies & neuropsychology are compatible |
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α Image Analysis & Quantification (3-D)
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o Recent advance in computer software have allowed three-dimensional computer reconstruction of specific brain structures
o Such 3-D images advance the understanding of pathologic conditions as well as brain structures, because scientists can now visualize the site of the lesion from any angle or perspective o As technology develops further, it will be possible to increase the combination & integration of imaging techniques o However, as with any research, neuropsychological theory is needed to guide explorations of how brain activity relates to behavior |
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α Future Directions
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o The human brain is the most complex structure known in the entire universe
o The challenge before cartographers of the new millennium is to map function; what brain structures do what, & when o The new imaging technologies are capable of examing the normal, healthy functioning brain o The most exciting use of neuroimaging, we purpose, is in combination with neuropsychological procedures o New advances will also demonstrate brain activity from moment to moment in real time with precise localization o This direction will lead to a multidimensional & increasingly comprehensive approach to the functioning of the brain, bridging the gap between psychology & biology |