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It is very unlikely that a ocular/orbital dermoid cyst is in any way related to her petite seizures. There is the slight chance that, if her "dermoid" was located on the medial aspect of her orbit, it may have been a encephalocele and not a dermoid after all.
If this were indeed the case, and I'm not saying that it is, then an encephalocele could be associated with neurological problems. It would be very, very unlikely that this diagnosis would have been missed for two decades. An MRI, which you said your daughter has had in the past would easily have diagnosed this condition.
So the take home response to your question? I don't think her past diagnosis of a dermoid cyst is in any way related to her new onset seizure activity.
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