The historical development of the pseudotumor concept.

The author outlines the history of the development of the pseudotumor concept, first specifically formulated by Nonne in 1904 but implicit in earlier descriptions. A scheme of periodization is applied, identifying otological, neurosurgical, neurological, and neuroophthalmological periods; he relates theoretical and practical developments in the understanding of the condition to the concerns of the dominant speciality involved in diagnosis and management. Key studies from each period are discussed in relation to the issues of mechanism, origin, nomenclature, diagnosis, and treatment. During the otological period, approaches to the condition were heavily influenced by its common association with middle ear infection, often with venous sinus involvement, and this led to the idea of disturbed cerebrospinal fluid dynamics as the cause. The advent of neuroradiological systems ushered in the neurosurgical period in which the significant but unfinished debate began: which intracranial compartment is primarily implicated in the intracranial hypertension? By the time of the neurological period cerebral edema was implicated as the cause, and this coincided with the availability of appropriate treatment methods and steroidal and diuretic agents. Toward the end of this period additional major advances in investigative methods again brought the issue of mechanism into contention, although a resolution was not to follow. The neuroophthalmological period is characterized by an increased awareness of the significance of visual loss and a return to one of the original methods of treatment. Finally, the possible significance of impaired cranial venous outflow, a thread running through all periods, is considered.