In this study we aimed to investigate the excitability of both the primary motor cortex and the primary visual cortex in patients affected by idiopatic generalized epilepsy (IGE) with/without photosensitivity. Using transcranial magnetic stimulation we determined the resting motor threshold (rMT) and the phosphene threshold (PT) in 33 patients with IGEs (8 with photosensitivity), compared with 12 healthy controls. An inversion of the PT/rMT ratio (PT/rMT ratio <1) was found in 87.5% epileptic patients with photosensitivity. All patients with active epilepsy and photosensitivity showed this inversion. The differences in the PT/rMT ratio of epilepsy patients with photosensitivity and those of healthy controls (p=0.007) and with epilepsy patients without photosensitivity (p=0.016) were statistically significant. 91.7% of the controls reported phosphenes, compared with 45.5% of patients with idiopathic generalized epilepsy (p=0.015). Phosphenes were reported more frequently among epilepsy patients with photosensitivity (87.5%) than in patients with active epilepsy without photosensitivity (30.8%) (p=0.038) and with patients with epilepsy in remission without photosensitivity (33.3%) (p=0.054). No differences were found between epilepsy patients with photosensitivity and controls (p=0.648). The marked decrease in PT and the high phosphene prevalence in epilepsy patients with photosensitivity indicate a regional hyperexcitability of the primary visual cortex. Results of our study argue therefore against the presence of homogeneously distributed hyperexcitability in idiopathic generalized epilepsies associated with photosensitivity. If confirmed by further studies, transcranial magnetic stimulation with the assessment of rMT and PT might be a useful and fascinating method with which to study pathophysiological mechanisms underlying photosensitivity.
Ipereccitabilità della corteccia visiva primaria nelle epilessie generalizzate idiopatiche associate a fotosensibilità: Uno studio mediante stimolazione magnetica transcranica | [Visual cortex hyperexcitability in idiopathic generalized epilepsies with photosensitivity: A TMS study]
BRIGO, Francesco;ROSSINI, Fabio;MANGANOTTI, Paolo;BONGIOVANNI, Luigi Giuseppe
2013-01-01
Abstract
In this study we aimed to investigate the excitability of both the primary motor cortex and the primary visual cortex in patients affected by idiopatic generalized epilepsy (IGE) with/without photosensitivity. Using transcranial magnetic stimulation we determined the resting motor threshold (rMT) and the phosphene threshold (PT) in 33 patients with IGEs (8 with photosensitivity), compared with 12 healthy controls. An inversion of the PT/rMT ratio (PT/rMT ratio <1) was found in 87.5% epileptic patients with photosensitivity. All patients with active epilepsy and photosensitivity showed this inversion. The differences in the PT/rMT ratio of epilepsy patients with photosensitivity and those of healthy controls (p=0.007) and with epilepsy patients without photosensitivity (p=0.016) were statistically significant. 91.7% of the controls reported phosphenes, compared with 45.5% of patients with idiopathic generalized epilepsy (p=0.015). Phosphenes were reported more frequently among epilepsy patients with photosensitivity (87.5%) than in patients with active epilepsy without photosensitivity (30.8%) (p=0.038) and with patients with epilepsy in remission without photosensitivity (33.3%) (p=0.054). No differences were found between epilepsy patients with photosensitivity and controls (p=0.648). The marked decrease in PT and the high phosphene prevalence in epilepsy patients with photosensitivity indicate a regional hyperexcitability of the primary visual cortex. Results of our study argue therefore against the presence of homogeneously distributed hyperexcitability in idiopathic generalized epilepsies associated with photosensitivity. If confirmed by further studies, transcranial magnetic stimulation with the assessment of rMT and PT might be a useful and fascinating method with which to study pathophysiological mechanisms underlying photosensitivity.
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