Approach to the patient with transient alteration of consciousness.

Evaluating transient impairment of consciousness is critical to diagnose epileptic seizures, syncope, parasomnias, organic encephalopathies, and psychogenic nonepileptic seizures. Effective evaluation of episodic unconscious events demands interactive interviewing of the patient and witnesses of the events, with judgment as to historians' observational abilities. When generalized tonic-clonic seizures have been witnessed by medical staff or other reliable observers, a search for concomitant nonconvulsive events and for comorbid illnesses often elucidates diagnoses unsuspected by the referring physician. Consultation for stupor-coma should not miss a potentially reversible acute severe encephalopathy, particularly when reversibility requires timely therapy. Perspicacious analyses of complex cognitive-motor phenomena support judicious application of diagnostic procedures, including brief or prolonged EEG and video-EEG, EKG tilt-table testing, EKG loop monitoring, and brain imaging.