In vivo study indicating loss of intracortical inhibition in tumor-associated epilepsy
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Published on: April 21, 2023
Kerstin Irlbacher1, Stephan A Brandt, Bernd-Ulrich Meyer
1Department of Neurology, Charité, Humboldt-University, Berlin, Germany. kerstin.irlbacher@charite.de
Abstract:
Transcranial magnetic stimulation was performed in 2 patients with focal motor seizures in the right hand caused by a circumscribed tumor process affecting the left precentral gyrus. In both cases, paired-pulse transcranial magnetic stimulation showed a loss of intracortical inhibition for interstimulus intervals of 2 to 4msec that was replaced by an enormous facilitation in the lesioned hand motor cortex. The uniform impairment of inhibitory mechanisms in epileptogenic tumors with different histologies suggests a common, nonspecific cause of tumor-related epileptogenesis.
Insights
Researchers used transcranial magnetic stimulation to study focal motor seizures in patients with brain tumors. They found a loss of inhibition and increased facilitation in the affected motor cortex, suggesting a common cause for tumor-related epilepsy.
Area of Science:
- Neuroscience
- Epileptology
- Neurosurgery
Background:
- Focal motor seizures can arise from circumscribed brain tumors.
- The precentral gyrus is critical for motor control.
- Understanding the neurophysiological basis of tumor-related epilepsy is important.
Purpose of the Study:
- To investigate intracortical inhibition and facilitation in patients with focal motor seizures due to brain tumors.
- To explore the common mechanisms underlying epileptogenesis in tumorous lesions.
Main Methods:
- Paired-pulse transcranial magnetic stimulation (TMS) was applied to the left precentral gyrus in two patients.
- TMS assessed intracortical inhibition and facilitation at specific interstimulus intervals (2-4msec).
Main Results:
- A loss of intracortical inhibition was observed in the lesioned motor cortex.
- This was accompanied by significant intracortical facilitation at short interstimulus intervals.
- These findings were consistent across patients despite potential differences in tumor histology.
Conclusions:
- Impaired inhibitory mechanisms are a common feature of epileptogenic tumors.
- Tumor-related epileptogenesis may stem from a shared, non-specific disruption of cortical inhibition.
- These findings advance the understanding of epilepsy associated with brain tumors.
