EEG, NCS, EMG Flashcards
What are PLED’s?
periodic lateralizing epileptiform discharges (PLEDs): may occur with any acute focal cerebral insult (e.g. herpes simplex encephalitis (HSE), abscess, tumor, embolic infarct): seen in 85% of cases of HSE (onset 2–5 d after presentation), if bilateral is ≈ diagnostic of HSE
What is SSPE?
Subacute sclerosing panencephalitis (pathognomonic pattern): periodic high voltage with 4–15 secs separation with accompanying body jerks, no change with painful stimulation (differential diagnosis includes PCP overdose)
What EEG pattern is seen in CJD?
bilateral sharp wave 1.5–2 per second (early → slowing; later→ triphasic). May resemble PLEDs, but are reactive to painful stimulation (most PLEDs are not)
What frequency are alpha waves?
8-13Hz
What frequency are theta waves?
4-7Hz
What frequency are delta waves?
0-3Hz
What frequency are Beta waves?
> 13Hz
What do you look for on EEG to confirm burst suppression?
Bursts of 8–12 Hz electrical activity (lasting 1–10 s) that diminish to 1–4 Hz prior to intervals of electrical silence (no excursions ≥ 5 microvolts, lasting > 10 s)
What would an increased latency on BAER between I and III suggest?
Lesion between Pons and colliculus - (Vestibular schwannoma)
What would and increased latency on BAER between III and V suggest?
Lesion between lower pons and midbrain - (MS)
Can a patient having intra-op SSEPs be paralysed?
Yes - reduces muscle artefact but will be unable to see a visible twitch that confirms the stimulus is being received.
What are the contraindications to MEP monitoring?
history of epilepsy/seizures
past surgical skull defects
metal in head or neck
use special care with implanted electronic devices
When would you be concerned with changes in EP?
Any of the following:
SSEP:
50% decrease in peak signal amplitude from baseline
increase in peak latency > 10%
complete loss of a waveform
TCMEP: sustained 50% decrease in signal amplitude
DEP: decrease in signal of > 60%
What is the Stagnara wake up test?
An intraoperative test of voluntary motor function during spine surgery. - described in a publication dated 1973!
What are fasciculation potentials typically associated with?
MND