5.11 Principles of Diagnostic Tests For Nervous Disorders

Several diagnostic tests have been developed for nervous disorders. These tests help in identifying and localizing abnormalities in the brain and nervous system. The main diagnostic tests discussed are Electroencephalography (EEG), Computed Tomography (CT) Scan, and Magnetic Resonance Imaging (MRI).

Definition

Diagnostic Tests for Nervous Disorders: Diagnostic tests for nervous disorders are medical procedures used to detect and localize abnormalities in the brain, spinal cord, and nervous system.

Main Idea

• Several diagnostic tests have been developed for nervous disorders.
• The principles of EEG, CT scan, and MRI are discussed.
• EEG records electrical activity of the brain.
• CT scan uses X-rays and a computer to generate cross-sectional views.
• MRI uses magnetism, radio waves, and a computer to produce images.

Core Concept

• EEG = Electroencephalography; records brain waves
• CT scan = Computed Tomography; X-ray procedure
• MRI = Magnetic Resonance Imaging; uses magnetism and radio waves
• EEG = records electrical activity
• CT scan = generates cross-sectional views
• MRI = produces detailed images

Detailed Explanation

Electroencephalography (EEG)

• Neurons within the cerebral cortex continuously generate electrical activity.
• This activity can be recorded by electrodes attached to precise locations on the scalp, producing an electroencephalogram.
• This technique is called electroencephalography (EEG).
• An EEG pattern is commonly called brain waves.

Computed Tomography Scan (CT Scan)

• Computerized tomography is more commonly known by its abbreviated name, CT scan.
• It is an X-ray procedure that combines many X-ray images with the aid of a computer to generate cross-sectional views and, if needed, three-dimensional images of the internal organs and structures of the body.
• A CT scan is used to define normal and abnormal structures in the body and/or assist in procedures by helping to accurately guide the placement of instruments or treatments.

• In CT Scan a large donut-shaped X-ray machine or scanner called tomograph takes X-ray images at many different angles around the body.
• These images are processed by a computer to produce cross-sectional pictures of the body.
• In each of these pictures the body is seen as an X-ray "slice" of the body, which is recorded on a film.
• This recorded image is called a tomogram.

Magnetic Resonance Imaging (MRI)

• Magnetic Resonance Imaging (MRI) scan is a radiology technique that uses magnetism, radio waves, and a computer to produce images of body structures.
• The MRI scanner is a tube surrounded by a giant circular magnet.
• The patient is placed on a moveable bed that is inserted into the magnet.
• The patient is exposed to strong magnetic field and beam of radio waves.
• The receiver information is processed by a computer, and an image is produced.
• The image and resolution produced by MRI is quite detailed and can detect tiny changes of structures within the body.

Skills: Interpreting and Communication

Conceptualize the Activity of Brain as an Electrical Activity

• Scientists have attempted to conceptualize electrical activity of the brain as a reflection of mental processes.
• Due to recent advances in computer software and hardware it is now possible to sample more electrical information from the brain by using different radiologic imaging techniques such as CT scan, MRI Scan and EEG.
• Therefore, these techniques have become very useful for the diagnosis of brain disorders.

Compare EEG of the Brain of a Sleeping Human with That of a Fully Awake Individual

• During wakefulness, alpha and beta activities are experienced in the human brain.
• Alpha activities consist of medium frequency waves.
• Beta activities consist of irregular low amplitude waves which are present when the individual is very alert and attentive.
• As the individual gets drowsy, brain experiences theta activities. This is the transition stage between wakefulness and sleep.
• Sleeping stage contains irregular theta activities where sleep spindles (short bursts of waves of 12-14 Hz) and K complexes (sudden sharp wave forms) are present.
• Then the next stage of sleep contains high-amplitude delta activities 20 to 50 percent of the time.

Summary Table of Diagnostic Tests

EEG Waves

Intermediate Level

Diagnostic Tests for Nervous Disorders

EEG Waves

Comparison of CT Scan and MRI

Formula / Mathematical Form

Not applicable to this topic.

Solved Example

Not applicable to this topic (descriptive topic).

Important Points

• 1. Several diagnostic tests have been developed for nervous disorders.
• 2. EEG records electrical activity of the brain.
• 3. EEG uses electrodes on the scalp.
• 4. EEG produces brain waves.
• 5. CT scan uses X-rays and a computer.
• 6. CT scan produces cross-sectional views.
• 7. CT scan can produce three-dimensional images.
• 8. CT scan is used to define normal and abnormal structures.
• 9. CT scan helps guide procedures.
• 10. MRI uses magnetism, radio waves, and a computer.
• 11. MRI scanner is a tube surrounded by a giant circular magnet.
• 12. MRI produces detailed images.
• 13. MRI can detect tiny changes in structures.
• 14. Alpha and beta activities occur during wakefulness.
• 15. Theta activities occur when drowsy.
• 16. Sleep spindles and K complexes occur during sleep.
• 17. Delta activities occur during deep sleep.
• 18. EEG, CT scan, and MRI are useful for diagnosing brain disorders.
• 19. These techniques are painless and non-invasive.
• 20. They help in identifying and localizing abnormalities.

Remember

• - EEG = Electroencephalography; records brain waves
• - CT scan = Computed Tomography; X-ray procedure
• - MRI = Magnetic Resonance Imaging; uses magnetism and radio waves
• - EEG = records electrical activity
• - CT scan = generates cross-sectional views
• - MRI = produces detailed images
• - Alpha = medium frequency; wakefulness
• - Beta = irregular low amplitude; alert
• - Theta = drowsy; transition to sleep
• - Delta = high amplitude; deep sleep

Common Mistakes

• 1. Confusing EEG, CT, and MRI — EEG = electrical activity; CT = X-rays; MRI = magnetism.
• 2. Thinking CT scan uses magnetism — CT scan uses X-rays.
• 3. Thinking MRI uses X-rays — MRI uses magnetism and radio waves.
• 4. Forgetting the role of EEG — Records brain waves.
• 5. Mixing up the brain waves — Alpha, beta, theta, delta.
• 6. Thinking CT scan is better than MRI — MRI has better resolution for soft tissues.
• 7. Believing these tests are invasive — They are non-invasive.
• 8. Forgetting the use of CT scan in guiding procedures — It helps guide instruments.
• 9. Mixing up the states associated with brain waves — Alpha/beta = awake; theta = drowsy; delta = deep sleep.
• 10. Thinking EEG is only for epilepsy — EEG is used for various brain disorders.

Quick Revision

These days a number of diagnostic tests have been developed for nervous disorders. The principle of EEG, CT scan and MRI are discussed here. Neurons within the cerebral cortex continuously generate electrical activity. This activity can be recorded by electrodes attached to precise locations on the scalp, producing electroencephalogram and this technique is called electroencephalography (EEG). An EEG pattern is commonly called brain waves. Computerized tomography is more commonly known by its abbreviated names, CT scan. It is an X-ray procedure that combines many X-ray images with the aid of a computer to generate cross-sectional views and, if needed, three-dimensional images of the internal organs and structures of the body. Magnetic Resonance Imaging (MRI) scan is a radiology technique that uses magnetism, radio waves, and a computer to produce images of body structures. The MRI scanner is a tube surrounded by a giant circular magnet. The patient is placed on a moveable bed that is inserted into the magnet. The image and resolution produced by MRI is quite detailed and can detect tiny changes of structures within the body.

60-Second Revision

• EEG = Electroencephalography; records brain waves
• CT scan = Computed Tomography; X-ray procedure
• MRI = Magnetic Resonance Imaging; uses magnetism and radio waves
• EEG = records electrical activity
• CT scan = generates cross-sectional views
• MRI = produces detailed images
• Alpha = medium frequency; wakefulness
• Beta = irregular low amplitude; alert
• Theta = drowsy; transition to sleep
• Delta = high amplitude; deep sleep
• Warning: CT scan uses X-rays; MRI uses magnetism and radio waves

CHAPTER COMPLETED

• Chapter Completed:
• 5. Nervous System of Man

• Next Chapter:
• 6. Endocrine System of Man

• First Topic:
• 6.1 HORMONES

Source:

Shall I start the next chapter?