Flashcards in EEG Deck (18)
What does the EEG measure?
potential difference btw 2 points. It changes continuously because electric fields generated by the brain change continuously.
How is EEG data presented?*
as a montage: display of data in an orderly arrangement. Shows the SPATIAL DISTRIBUTION of a changing electrical field. Odd numbers on the left, even numbers on the right.
What generates the potentials we see in EEG?*
summed synaptic potentials from a large population of neurons behaving as an electrical dipole. often the cortical pyramidal cells.
Also, EPSPs and IPSPs (exitatory and inhibitory post-synaptic potentials).
What are the groups of montages?
referential, where the reads are compared to a common reference, vs. bipolar, where neighboring electrodes are compared.
What should I be aware of technincally when interpreting EEG?*
EEG measures very small voltages- microvoltages*. so artifacts can have a huge impact!
What are the EEG artifacts I should consider from the environment?
instrumentation, electrode problems (sweat most common), electrical interference (cardiac monitors or IV pumps)
What are the physiologic artifacts I should consider when evaluating EEG?
Bioelectrical: cardiac/respiratory activity
eye movements (different parts of the eye are electronegative vs positive- retina is negative, cornea is positive)
muscle movement (neuromuscular transmission and muscle contraction are EC processes)
What physiologic factors affect the EEG?*
Age (newborns vs. kids. vs. teens vs. adults vs. elders)
level of arousal (wake vs. sleepy vs. sleeping)
meds (barbiturates and benzos; phenytoine, cabamazepine; lithium)
Also, there are many benign variants.
What are some activities that may provoke EEG findings?
sleep, lights, hyperventilation
What is the order of increasing frequency of the waves in eeg? what is the definition of each wave?*
delta: less than 4 Hz (cycles/s)
DTAB: Demon Trolls Adore Brains.
What are spikes and sharps?
spikes: less than 70 ms in duration -usually negative and abnormal
sharp: 70-200 ms. usually neg. sometimes normal, sometimes not.
What is posterior dominant rhythm? What is normal? *
important part of the EEG. should be slower freq (alpha) and higher volatge than the anterior parts. Normal is 8.5-11.5 alpha frequency.
What is the significance of focal slowing?*
focal functional abnormality
What is the significance of generalized slowing? What else may indicate this?*
encephalopathy may also be seen as a loss of expected organization
What is the significance of lots of spikes and sometimes sparks?*
What is the significance of PLEDs?*
PLEDs= periodic lateralized eleptiform discharges. indicate destructive brain process.
What is the significance of triphasic waves?*
metabolic encephalopathy; usually hepatic/renal, but may be hypoxic/ischemic encephalopathy