The clinical syndrome variously called benign myalgic encephalomyelitis, Iceland disease and epidemic neuromyasthenia.

Recent technical advances have added greatly to the ease with which virological methods may be applied to the study of poliomyelitis and allied infection of the central nervous system. These techniques have already borne abundant fruit in the development of a vaccine against poliomyelitis. The accurate appraisal of the preventive value of such a vaccine will depend on our ability to diagnose poliomyelitis accurately. It had long been believed that the clinical features of acute paralytic poliomyelitis were sufficiently characteristic for a confident diagnosis to be made on clinical grounds alone. This confidence has recently been shaken by the finding that the virus of louping-ill (Russian spring–summer encephalomyelitis) may produce a similar clinical picture, even in the United Kingdom. There is also suggestive but incomplete evidence that Coxsackie B, Echo and other viruses may occasionally cause acute flaccid paralysis. The position of a “non-paralytic” poliomyelitis is even less secure and the diagnosis can no longer be established on clinical grounds alone. The purpose of this article is to review a number of obscure outbreaks of paralytic illness, the majority of which were at first confused with poliomyelitis but which were later differentiated on clinical and epidemiologic grounds. Although investigations have been restricted by the fact that no deaths have occurred, the most careful virologic studies have failed to incriminate the polio virus, the Coxsackie or Echo groups of organisms, or any other known neurotrophic agent. The outbreaks will be compared, and the basis for the view that they constitute a clinical entity will be discussed. Such information as is available about the etiology, prognosis and treatment will be reviewed.