II. Background
- Measures electrical activity of cerebral cortex via sampled electrodes placed over the surface of the scalp
- Measures gray matter function (Neuronal function)
- Normal in white matter disease
III. Findings: Brain Wave Types
- Beta Waves
- Frequency >13 Hz
- Fine, medium amplitude wave form
- Seen in an alert patient
- Alpha Waves
- Frequency 8-13 Hz
- Seen in a quiet but awake patient or during REM Sleep
- Low amplitude wave form
- Theta Waves
- Frequency 4-7 Hz
- Seen in drowsy patients
- Delta Waves
- Frequency <4 Hz
- Seen in deep, non-REM Sleep patient
IV. Findings: Pathologic Brain Waves
- Flat Line
- Seen in brain death, as well as some Medication Overdoses
- Diffuse Slowing
- Organic brain syndrome or post-ictal state
- Localized Slowing
- Focal neurologic lesion
V. Findings: Seizure Disorder findings
- Indications
- Non-Seizure Times
- Abnormal in 70% of Seizure patients
- During Generalized Tonic Clonic Seizure
- Massive electrical discharge with high frequency, high amplitude waves
- During Focal Seizure
- Localized Seizure activity
- During Petit Mal Seizure
- Spike and Dome wave pattern
- Post-ictal
- Slowing of EEG
- Medications that do not affect EEG
- Anticonvulsants
- Medications that cause Beta (fast wave patterns)
VI. Findings: Cerebrovascular Accident (CVA) assessment
- Cortical CVA (large vessel disease)
- Abnormal EEG
- Subcortical or Brainstem CVA (small vessels disease)
- Normal EEG
VII. Findings: Metabolic encephalopathy
- Non-focal slowing of EEG
- Rhythmic bursts of symmetrical frontal slowing
- Specific patterns may assist with etiology
- Hepatic Encephalopathy: Triphasic waves