[wineeg] Drop in amplitude right hemisphere?
- From: Joe Siri Ekgren <vennskap@xxxxxxxxx>
- To: wineeg@xxxxxxxxxxxxx
- Date: Thu, 21 Aug 2003 14:36:03 +0200
Dear Listmembers,
I have an EEG with EO/EC/task that with a referential montage (linked
ears) that shows low amplitude in F8-T4-T6 with lowest amplitude in
T4.The topo maps of the qEEG show a black brim along this
localization in all bandranges. The impedance was between 1- 2.5 kOhm
in all leads.
A different montage, averaged reference shows less of the brim but
there still is a decrease in amplitude compared to right side.
I used the electro-cap. The same trend is seen when using another set
of electrodes in a different eeg 3 months ago. No other patients have
this trend.
In theory what might cause this?
Will temporal cortical activity picked up at the right earlobe
diminish the activity seen in the nearby electrodes, especially in a
referential montage? An EKG artefact found in the other leads also
vanishes in F8-T4-T6.
I am thinking of alternatives
increased skull thickness,
a slow expansive process (hematoma, tumour) between the
cortex and the skull at T4
Can one have problems with electrode function even with a good impedance?
Also, there might be some hardware issue since A2 almost always has a
kOhm or so higher impedance than A1. A2 was higher than A1 even after
keeping the electrodes in place and trading the place of the A1 jack
with the A2 jack. I expected the A1 to show the higher impedance but
the A2 remained higher than A1. Is there an amplifier problem in all
of this.
Questions, questions...
Thank you in advance for any help and ideas.
--
Joe
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