It may have an abnormal frequency, height or shape. This can be a general change in the way a normal brain wave looks. The other way an EEG can show abnormal results is called non-epileptiform changes. Called the Neuropsychiatric EEG-Based Assessment Aid (NEBA) System, this noninvasive scan measures slow brain waves called theta waves and fast brain waves called beta waves. The FDA approved the use of electroencephalogram (EEG) to diagnose ADHD in 2013. The different types of generalized seizures are:absence seizures (formerly known as petit mal)tonic-clonic or convulsive seizures (formerly known as grand mal)atonic seizures (also known as drop attacks)clonic seizures.tonic seizures.myoclonic seizures. When the diagnosis is based largely on an abnormal EEG, no amount of subsequent normal EEGs will ‘cancel’ the previous abnormal one, and the wrong diagnosis is very difficult to undo. The consequences of being misdiagnosed with epilepsy are obvious and serious. The topologic usefulness of EEG is limited, although it may be improved with computerization. In general, MRI is good at telling us where the lesion is, whereas EEG is good at separating normal and abnormal primarily cortical function.
To complicate this further, some people have ‘abnormal’ EEGs but do not have epilepsy. This means that sometimes the EEG is described as ‘abnormal’ (that is ‘not normal’ brain activity) but does not ‘prove’ that the person has epilepsy.