I have an avm over my primary and secondary motor cortex focal seizures to right upper extremities didn't show on eeg . why not?

Negative EEG: The eeg is often normal in people with focal seizures, especially if the seizure occurs without loss of consciousness. This is because a seizure has to involve a minimum area of cortex for it to be seen on the surface of the scalp. The signal is attenuated through bone and scalp. Also, a seizure focus can occur deep inside or be oriented parallel to the scalp and not be seen on eeg.