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Old 06-18-2011
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Question NBME Form 7 Tested concept

If you have not taken NBME 7 yet, please do not read further

There was a question about the pathogenesis of Absence seizures. Anyone know what it is?

It apparently is not spreading depression of cortical neurons
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Old 06-18-2011
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Post Abscence seizure

The basic underlying mechanism appears to involve

1- thalamocortical circuitry and
2- the generation of abnormal oscillatory rhythms from that particular neuronal network.

Biochemical mechanisms operative within thalamocortical circuitry during this neuronal oscillation seem to entail

1- phase-locked gamma-aminobutyric acid (GABA)B-mediated inhibition

2- alternating with glutamate-mediated excitation.

The basic cellular mechanism operative within this tension
between excitation and inhibition appears to involve the T-type calcium current.
Local circuitry within the thalamus may influence these oscillatory rhythms by GABAA-mediated inhibition

Pharmacological factors at play external to thalamocortical circuitry include
1- cholinergic,

2- dopaminergic, and

3- noradrenergic mechanisms.

Pathways that utilize these various neurotransmitters project onto the thalamus and/or cortex from sites distant to those structures and may modulate the process either up or down.
Perturbation of one or more of these neuronal networks may lead to abnormal neuronal oscillatory rhythms within thalamocortical circuitry, with a resultant generation of bilaterally synchronous spike wave discharges that characterize generalized absence seizures

(source www.ionchannels.org)
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Old 06-18-2011
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Thanks!

I couldnt find an explanation in my notes or on Uptodate.
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Old 06-18-2011
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Default pathophys of absence seizure

Hi, @apx85,
did this make any sence with respect to ur question (can ur question be answered from the above source, as it is complicated for me
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Old 06-18-2011
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Well according to the answer choice, it is a synchronized discharge of thalamocortical neurons that leads to the absence seizure
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