Transient hemiplegias are most often encountered in the aged and the sclerotic. The usual explanation of such an occurrence is that there has been a vessel spasm causing a temporary localized cerebral anemia (Langwill,1 Edgeworth,2 Heard,3 Osler,4 Allan,5 Russell6 and Parker7). There are facts supporting such a possibility, but also many points which make it seem unlikely and an unsatisfactory explanation.
In support of the theory of vessel spasm, vasomotor nerves have been noted in cerebral vessels and cerebral arteries show muscular tissue. Certain clinical reports give presumptive evidence in support of vessel spasm as a possibility. Osler reports an instance in an individual with Raynaud's disease in whom vessel spasm in the extremities with characteristic manifestations alternated with transient cerebral attacks. The ophthalmologists report spasm of retinal arteries in certain cases of migraine. Florey8 in recent work has demonstrated that cerebral