The photoparoxysmal response (PPR), also referred to as photosensitivity, is defined as the abnormal occurrence of cortical spikes or spike and wave discharges on electroencephalogram (EEG) in response to intermittent light stimulation (Doose and Waltz, 1993).
Photosensitivity is a frequent finding in patients with idiopathic generalized epilepsy (see 600669), especially those with juvenile myoclonic epilepsy, suggesting a common epileptogenic pathway for both phenomena. The comorbidity of the 2 disorders suggests that presence of PPR may also increase the risk for epilepsy (Stephani et al., 2004; Tauer et al., 2005).
Genetic Heterogeneity of Photoparoxysmal Response
The PPR1 locus has been mapped to chromosome 6p21. See also PPR2 (609572), mapped to chromosome 13q31, and PPR3 (609573), mapped to chromosome 7q32. [from
OMIM]