Abstracts

Self-induction in photosensitive patients is a relatively rare phenomenon. Because of the intriguing phenomenon, mainly individual cases have been described so far and little is known about the clinical and EEG features these children and adolescents have in common. Many patients admit their behaviour of compulsive eye blinking or handwaving in telling that they get a nice feeling by it or use it as a way of relaxation or escape. Detection depends largely on the duration of the EEG registration, intensity of surrounding light (preferably sunlight), registration while seated (the eyes can be turned upwards toward the lights) and feeling comfortable with the doctors and technicians.
We have studied many patients in detail over the years to try to find out what mechanisms are behind this. What are the differences with other photosensitive patients in clinical and neurophysiological aspects?
Our hypothesis is that the evoked discharges should be generalised and of rather short duration. Because of the likelyhood that the limbic system is involved the evoked epileptic activity will be predominantly R-sided. and and different from the non- self-inducing photosensitive patients . Over a period of 20 years, 55 self inducing patients have been diagnosed and have been selected for further analyses of clinical and EEG data comprising intensive EEG monitoring data. In all patients repeated IPS testing was done using a Grass PS 33 stimulator as well as stimulation with black and white striped patterns. Clinical data have been gathered and in one third a long term follow up was established.
Detailed analysis of EEG abnormalities during IPS and pattern was done at the time and could be reviewed for our purposes. The data from the self inducers were compared with similar historical data gathered over the same time span in photosensitive patients. The self inducing patients were for the vast majority between 10 and 25 years of age when they were diagnosed as being self inducers, corresponding with the age of maximal expression in photosensitive patients. Although the majority [ldquo]used[rdquo] sunlight, 6% of children used predominantly high contrast patterns like curtains etc. None had IOPE.Myoclonic jerks were not evoked apart from eyelid myoclonia and most evoked discharges were subclinical. All patients had generalised short lasting EEG discharges and in 75% a clear R-sided beginning or maximum could be registered. Self-inducing patients are a special type of photosensitive patients with typical clinical manifestations as well as EEG phenomena. The compulsive behaviour can indeed be linked with stimulation of the limbic system .PET and fMRI studies can elucidate that further.