Visual cortex hyperexcitability in idiopathic generalized epilepsies with photosensitivity: a TMS pilot study

Epilepsy Behav. 2013 May;27(2):301-6. doi: 10.1016/j.yebeh.2013.02.010. Epub 2013 Mar 18.


Background: The current understanding of the mechanisms underlying photosensitivity is still limited, although most studies point to a hyperexcitability of the visual cortex.

Methods: 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.

Results: Eleven controls (92%) reported phosphenes compared with fifteen (46%) patients with idiopathic generalized epilepsy (p=0.015). Phosphenes were reported more frequently among patients with epilepsy with photosensitivity (87.5%) than in patients with active epilepsy without photosensitivity (30.8%) (p=0.038) and patients with epilepsy in remission without photosensitivity (33.3%) (p=0.054); no differences were found between patients with epilepsy with photosensitivity and controls (p=0.648). Resting motor threshold and phosphene threshold were significantly higher among patients with epilepsy (active epilepsy or epilepsy in remission without photosensitivity) compared to healthy controls (p<0.01). Conversely, patients with active epilepsy and photosensitivity had significantly lower values than controls (p=0.03).

Conclusions: The marked decrease in PT and the high phosphene prevalence in patients with IGE with photosensitivity indicate a regional hyperexcitability of the primary visual cortex. Results of this study also suggest that the PT may serve as a biomarker for excitability in patients with IGE and photosensitivity.

MeSH terms

  • Adolescent
  • Adult
  • Analysis of Variance
  • Epilepsy, Generalized / complications
  • Epilepsy, Generalized / pathology*
  • Female
  • Humans
  • Linear Models
  • Male
  • Middle Aged
  • Phosphenes / physiology*
  • Photosensitivity Disorders / complications
  • Photosensitivity Disorders / pathology*
  • Pilot Projects
  • Sensory Thresholds
  • Transcranial Magnetic Stimulation*
  • Visual Cortex / physiopathology*
  • Young Adult