Photosensitivity Definitions Photosensitivity or visual sensitivity is abnormal sensitivity to light stimuli, detected usually with electroencephalography (EEG) as a paroxysmal reaction to intermittent photic stimulation (IPS). Photosensitivity is a broad term and is used both for (a) epileptiform EEG discharges and (b) epileptic seizures, evoked by visual stimuli. Several types of visual stimuli are known of which flickering sunlight or IPS, TV, videogames, and striped patterns are the most common. A photoparoxysmal EEG response is a localized or generalized epileptiform EEG reaction to IPS or stimulation with other stimuli; see Figs. 97.1 and 97.2 for examples of both types of photoparoxysmal responses (PPR). Photosensitivity is customarily divided into three groups: patients with visually induced seizures only, patients with photosensitivity and some other epileptic disorder, and asymptomatic individuals with PPR as an isolated finding (Kasteleijn-Nolst Trenité et al. 2001). During follow-up patients may shift from asymptomatic and from visually induced seizures only to the other categories. Some photosensitive patients can evoke generalized epileptiform discharges by fast eyelid fluttering and upward gaze or simply by eye closure: they are called auto- or self-inducers. There is some overlap with eyelid myoclonia with absences (EMA or EMEA) and self-induction (Striano et al. 2009). In this chapter we make a distinction between the epileptiform EEG responses to IPS, the PPRs (patients are photosensitive), and the seizures provoked by visual stimuli in daily life (visually induced seizures).
|Title of host publication||The Causes of Epilepsy: Common and Uncommon Causes in Adults and Children|
|Publisher||Cambridge University Press|
|Number of pages||8|
|ISBN (Print)||9780511921001, 9780521114479|
|Publication status||Published - Jan 1 2011|
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