Some examples of electroencephalogram readings include similar electrical wave patterns on both sides of a normal brain; too many theta waves due to a brain injury; sudden spikes of activity due to epilepsy; or a flat reading due to lack of oxygen to the brain, notes WebMD. An EEG measures the amount of activity in a person's brain. It records the activity as a series of wavy lines, states Mayo Clinic.
A doctor uses the results of an EEG to diagnose disorders of the brain, such as epilepsy, brain tumors, stroke and Alzheimer's disease, according to Johns Hopkins School of Medicine. For example, the EEG can show either a sudden spike of activity or slowing down of the waves. These changes can indicate a brain tumor, infection or stroke. In patients with epilepsy, the pattern and location of the spikes can show the physician the type of seizure. If these readings occur throughout the brain, they can indicate encephalitis, diabetic ketoacidosis or drug intoxication.
A EEG reading of too many theta waves or delta waves is caused by some medications or by a brain injury when it occurs in patients who are awake, notes WebMD. If the EEG reading has mostly alpha and beta waves in similar patterns on both sides of the brain, then the reading is normal. Coma patients, or those under severe sedation, may have a flat EEG reading, which means there is no brain function.