Thank you for your query.
Had you shared the reports of ultrasound
, CAT scan, EEG and EKG it would have been better for us to guide you. The seizures could be responsible for breath holding. As the doctors are investigating the cause (and there being no earlier history of seizures and breath holding) let us wait for their opinion. In the interim they must have put your grandson on some anti-convulsants to control the seizures.
I hope I have answered your query to your satisfaction.