Abstracts

Rationale: Different prevalence rates of generalized Photo-Paroxysmal Responses (PPRs) can be found in randomly selected epilepsy populations. A PPR is found in 5-8% of patients in the Netherlands, Germany, the UK, South Africa and Australia (Kasteleijn-Nolst Trenité, 1989; Danesi, 1985; Doose and Gerken, 1973; De Graaf, 1995, Nagarajan et al, 2003) but in only 1-2 % of patients in India, Japan, Nigeria and Zimbabwe (Saleem et al., 1994; Shiraishi et al., 2000; Danesi, 1985; Familusi et al., 1998). The majority of patients with a generalized PPR have a genetic generalized epilepsy, such as absence epilepsy, JME and Dravet syndrome, but PPRs occur regularly in patients with focal epilepsies as well. Ictal temporal lobe seizures have even been recorded during generalized PPRs (Kasteleijn- Nolst Trenite et al., Epilepsy Research 2017; 133: 113-120; ibid, pgs. 123-5). The question we address here is whether this difference in prevalence rates of generalized PPR in different genetic/ethnic groups is equally reflected in the prevalence rate of patients with focal epilepsy having a generalized PPR. Methods: We have analyzed studies in photosensitive patients from various continents and countries published between 1980 and 2016 to extract data concerning prevalence of focal epilepsy in PPR positive patients. Data from different genetic/ethnic groups were then analysed with 2-tailed Fisher’s Exact test. Results: A total of 20 informative studies has been found, covering 13 different countries worldwide (Europe #7, USA/Canada/Australia #4, Japan #4, India/Pakistan #3, Middle East #1 and Africa #1). From the total amount of 1,104 patients with a generalized PPR (54% Female; age range from 1-80 yr), 214 (19%) were classified as having focal epilepsy. The average prevalence of focal epilepsy plus PPR = 18%, ranging from 0.4-100%. Japan and India/Pakistan have the highest rates of focal epilepsy in photosensitive patients, respectively at 37% and 24%, while Europeans have 16%, and studies for patients from the USA/Canada/Australia 13%. For the Western population combined possessing a generalized PPR (n= 860), 134 (15.6%) patients had a generalized PPR + focal epilepsy; for the combined Eastern population (Japan/India/Pakistan) with a generalized PPR (n=214), 73 (34.1%) patients had a generalized PPR + focal epilepsy (p < 0.0001). Conclusions: The prevalence of focal epilepsy combined with photosensitivity (+PPR) in ‘Eastern’ countries seems to be higher than in ‘Western’ countries (mainly Caucasian), which is the opposite of the prevalence data of PPR known thus far. Prospective standardized studies are needed to confirm these findings. Funding: None