Syncope of obscure nature.

One hundred and eleven cases of syncope or loss of consciousness are analyzed. Most are of obscure nature while some illustrate features of syncope that deserve further scrutiny. The cases are divided into six groups: Resembling cardiac syncope (30 cases); vasovagal syncope (22 cases); features of both cardiac and vasovagal syncope (12 cases); orthostatic hypotensive (29 cases); akinetic seizure? (12 cases); and miscellaneous (5 cases). Some groups are subdivided according to the circumstances surrounding the spells, for example, seated eating, nocturnal, associated with bowel movement, response to anticonvulsant therapy, etc. The following conclusions seem warranted: The evidence favors the existence of a type of akinetic seizure resembling cardiac syncope; loss of consciousness while seated eating (prandial syncope) may comprise a syndrome; syncope related to bowel movement or abdominal pain is a striking association; sporadic nocturnal syncope due to temporary hyporeactivity of baroreceptors is not sufficiently recognized; alcohol ingestion may precipitate orthostatic hyporeactivity of baroreceptors is not sufficiently recognized; alcohol ingestion may precipitate orthostatic hypotension. Familial syncope, syncope proneness and cold drink syncope are illustrated.