What is the pathophysiology of absence seizures?

Updated: Sep 25, 2018
  • Author: Scott Segan, MD; Chief Editor: Selim R Benbadis, MD  more...
  • Print
Answer

Answer

The pathophysiology of absence seizures is not fully understood. In 1947, Jasper and Droogleever-Fortuyn electrically stimulated nuclei in the thalami of cats at 3 Hz and produced bilaterally synchronous spike-and-wave discharges on EEG. [21] In 1953, bilaterally synchronous spike-and-wave discharges were recorded by placing depth electrodes in the thalamus of a child with absence seizures. [22]

In 1977, Gloor et al demonstrated that the bilaterally synchronous, 3-Hz spike-wave discharges in the feline penicillin model of absence seizures were generated in the cortex. This led to the corticoreticular theory of primarily generalized seizures.

Abnormal oscillatory rhythms are believed to develop in thalamocortical pathways. This involves gamma-aminobutyric acid (GABA)-B–mediated inhibition alternating with glutamate-mediated excitation.

The cellular mechanism is believed to involve T-type calcium currents. T channels of the GABAergic reticular thalamic nucleus neurons appear to play a major role in the spike-wave discharges of the GABAergic thalamic neurons. [23]

GABA-B inhibition appears to be altered in absence seizures, and potentiation of GABA-B inhibition with tiagabine (Gabitril), vigabatrin (Sabril), [24] and, possibly, gabapentin (Neurontin), results in exacerbation of absence seizures. Enhanced burst firing in selected corticothalamic networks may increase GABA-B receptor activation in the thalamus, leading to generalized spike-wave activity.

These data suggest that activity of thalamic networks is necessary for spike-wave discharge rhythmogenesis, and cortical hyperexcitability is necessary for their generation. [25]

In symptomatic generalized epilepsies, absence seizures are due to a wide variety of causes that at an early stage of neural development, result in diffuse or multifocal brain damage. The causes and management of secondary generalized epilepsies, and the other seizure types that accompany them, are not discussed in this article.


Did this answer your question?
Additional feedback? (Optional)
Thank you for your feedback!