Electroencephalography (EEG) is the recording of electrical activity along the scalp. EEG measures voltage fluctuations resulting from ionic current flows within the neurons of the brain. In clinical contexts, EEG refers to the recording of the brain’s spontaneous electrical activity over a short period of time, usually 20–40 minutes, as recorded from multiple electrodes placed on the scalp. In neurology, the main diagnostics application of EEG is in the case of epilepsy, as epileptic activity can create clear abnormalities on a standard EEG study.^[A secondary clinical use of EEG is in the diagnosis of coma, encephalopathies, and bran death. EEG used to be a first-line method for the diagnosis of tumors, stroke and other focal brain disorders, but this use has decreased with the advent of anatomical imaging techniques with high (<1 mm) spatial resolution such as MRI and CT. Despite limited spatial resolution, EEG continues to be a valuable tool for research and diagnosis, especially when millisecond-range temporal resolution (not possible with CT or MRI) is required.

Echoencephalography
Category: Nervous system.
Subcategory: Non-invasive tests.
Material studied: Sonograms of brain structures.
Estimated cost of test: $275.00.
Patient time for test: 1+ hour.
Reliability of test results: Good.
Available as home self-test? No.

BEFORE THE TEST

Purpose of test:

• Determines position and size of several brain structures.
• Investigates suspected disease of soft tissues of the brain and spinal cord.Where is test performed?
• Commercial sonography laboratory, hospital, doctor’s office.Who performs test?
• Ultrasound technician.Risks and precautions:
• Metal objects may be attracted to the powerful magnet used in the procedure.Patient preparation:
• Activity–No changes necessary.
• Diet–No changes necessary.
• Medicines–No changes necessary.
• Disrobing–Remove all jewelry and metal objects from your head and neck.
  

  THE TEST

  Sensory factors:

• Touching–You may be uncomfortable for short periods when you assume the positions the technician requests. >Seeing–You will see strange-appearing heavy equipment in a small space.
• Hearing–You will hear the sounds of ultrasound machine.
• Feeling–You may feel intimidated by the large equipment. Some degree of apprehension or fear is normal and should be expected. This discomfort disappears when the test is completed. You may also feel uncomfortable for a short while if small, enclosed space causes you discomfort.
• Other senses (taste, smell)–Not affected.Equipment used:
• Echoencephalograph.
• Transducer.
• Oscilloscope.
• Water-soluble jelly.Description of test:
• Follow technician’s instructions for positioning your body.
• Technician guides a transducer, which may feel cold on your ski,.n, over the area of the brain to be examined.
• Transducer sends an ultrasound beam, which is composed of very high-frequency soundwaves inaudible to the human ear.
• After passing through tissue, reflected soundwaves are converted into electrical impulses and displayed on a video screen for interpretation or photographing for later interpretation.
  

  AFTER THE TEST

  Immediate post-test care:

• None.Activity after test:
• Return to pretest activities right away.Time before test results available:
• Time before results are reported to the doctor or patient varies from a few minutes to a few days.
  

  TEST RESULTS

  Test values:

• Test results are determined by interpretation of images.Normal values:
• Normal size, shape and density of structures in the skull.What ABNORMAL may indicate:
• Cerebral edema*.
• Space-occupying lesions*, such as tumors* or blood clots.
• Subdural and extradural hemorrhage.Taking these drugs may affect test results:
• None expected.Other factors that may affect test results:
• Failure to remove jewelry or metal objects from your head and neck.
• Two sets of identical impulses are required to confirm abnormal results. *See Glossary.