EEG is usually abnormal in all of the following conditions, EXCEPT:

Locked-in state is a type of pseudocoma in which an awake patient cannot speak or make any voluntary movement but retains the ability to make veical eye movements and lid elevation. On examination pupils are normally reactive. It is caused by infarction or hemorrhage in the ventral pons that transects descending coicospinal and coicobulbar pathways. In locked in state the EEG can be either normal or minimally slow. Ref: Harrison's Internal Medicine, 18th Edition, Chapters 274, 381; Clinical Neurology By Roger P. Simon, 7th Edition, Chapter 1; Current Medical Diagnosis and Treatment 2012, Chapter 32