Hello sir, by the detailed description that you have given, it seems that there is no pathological problem in the brain as the scans are clean, which means there is no tumour or blockage of any kind. Thus what we can assume is this symptom is arising due to sudden activity of neurons. Probably the signals transmitted between neurons are send out signals in a burst, which is leading to goose bumps. This may be a very very mild form of seizure , but it is not epilepsy as your father is not having any convulsions or unconsciousness spells. All this said, it is very difficult to prescribe a medicine for this condition without a thorough case study because it the matter of the brain, we should not take chances or experiment with medicine. If you wish for a homoeopathic treatment, kindly visit an experienced homoeopath in your area or write to me or add yourself in my patients and take an appointment .
Next Steps
The first step to control such episodes is to relax the brain. All kinds of abnormal brain activity which we cannot understand through brain scans, can be controlled through pranayam and meditation. Please ask your father to practice alternate nostril breathing also known as naadi shodhan, ans specially concentrate on "surya bhedi naadhi shodhan" please follow the link http://www.yoga-for-beginners-a-practical-guide.com/surya-bhedi.html . In addition to this, ask him to meditate for atleast 20 minutes everyday. He can do this before going to sleep.
Health Tips
Do not take stress, avoid blinking lights,watching TV in a dark room, use of ear phones or head phones for longer than 30 minutes in one sitting. Take proper rest and sleep.