Chapter 6

Front 1

MRI

Back 1

• 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.

Front 2

Neuronistology techniques

Back 2

• 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

Front 3

Golgi Stain

Back 3

• 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

Front 4

Nissl stain

Back 4

• 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

Front 5

Other staining techniques

Back 5

• Remains a viable method for studying cellular formation of nervous systems & helps neurosis in studying specialized contacts among neurons & their complex & often puzzling arrangements.

Front 6

Radiological Procedures

Back 6

• Rapid process of radiology has made a significant impact on field of clinical neurology & neuropsychology

Front 7

Skull X-ray

Back 7

• 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

Front 8

Air Encephalography (Pneumoencephalography)

Back 8

• 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

Front 9

Computed Transaxial Tomography Scan [CT]

Back 9

• 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.

Front 10

Progression of CT scan

Back 10

• 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.

Front 11

CT scan Procedure

Back 11

• 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.

Front 12

hyperdensity

Back 12

(typically signals abnormal density such as tumor or an internal bleed)

Front 13

hypodensity

Back 13

(associated with low density & perhaps an old lesion)

Front 14

CT scan continued

Back 14

• 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.

Front 15

Angiography

Back 15

• 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.

Front 16

Sodium-Amytal Injections (Wada)

Back 16

• 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”

Front 17

Electroencegraphy (EEG)

Back 17

• 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

Front 18

Hans Berger

Back 18

• 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

Front 19

EEG Recording

Back 19

• 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.

Front 20

Brain Waves

Back 20

• 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

Front 21

EEG & Epilepsy

Back 21

• 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

Front 22

• Primary referral for clinical EEG is to help diagnose:

Back 22

o Seizure disorder
o Sleep disorder
o Coma level
o Brain dead?
o Epilepsy

Front 23

EEG Interpretation

Back 23

• 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

Front 24

BEAM

Back 24

• 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

Front 25

BAER

Back 25

Brainstem Auditory Evoked Response
o Examiner presents clicks to each ear with headphones

Front 26

Evoked Potential (EP)

Back 26

• 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.

Front 27

Electrical Stimulation

Back 27

• 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.

Front 28

α Electromyography (EMG)

Back 28

the electrical analysis of muscles

o In EMG, diagnosticians perform a nerve conduction study of a specific muscle to diagnose neuromuscular disorders

Front 29

α Imaging of Brain Metabolism

Back 29

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

Front 30

α Regional Cerebral Blood Flow

Back 30

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

Front 31

α Single-Photon Emission Computed Tomography (SPECT)

Back 31

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

Front 32

PET Research

Back 32

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

Front 33

α Positron Emission Tomography (PET)

Back 33

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

Front 34

PET Measurement

Back 34

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

Front 35

α Magnetic Resonance Imaging (MRI)

Back 35

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

Front 36

Reading an MRI

Back 36

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

Front 37

fMRI

Back 37

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

Front 38

α Magnetoencephalography (MEG)

Back 38

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

Front 39

α Cerebrospinal Fluid Studies: Lumbar Puncture

Back 39

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

Front 40

CSF examination

Back 40

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

Front 41

α Neurologic Exam

Back 41

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

Front 42

α Neuropsychological Evaluation

Back 42

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

Front 43

α Image Analysis & Quantification (3-D)

Back 43

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

Front 44

α Future Directions

Back 44

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