Purpose: Previous studies have evaluated the inter-session variability of motor thresholds (MT), short intracortical inhibition and intracortical facilitation using paired pulse transcranial magnetic stimulation (TMS) in normal individuals. Here we evaluate the reproducibility of a range of measures of cortical excitability in patients with epilepsy.
Methods: Twenty-four drug naïve patients with newly diagnosed epilepsy (13 idiopathic generalised epilepsy [IGE], 11 focal epilepsy) and seventeen non-epilepsy controls were studied. Motor threshold (MT) at rest and recovery curves constructed using paired pulse stimulation at short (2-15 ms) and long (50-400 ms) interstimulus intervals (ISIs) were analysed on two separate occasions, 4-20 weeks apart. The Lin's concordance correlation coefficient test was used to measure agreement between the two sessions.
Results: Significant levels of agreement between the two sessions were observed at MT and all the ISIs measured. This was highest in non-epilepsy controls.
Conclusion: Cortical excitability measures are repeatable over time in both patients with epilepsy and healthy controls. Increased motor cortex excitability is a stable feature in epilepsy without significant inter-session variability.
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