Persons who have been working for considerable periods under a greatly increased atmospheric pressure, such as divers, or workers in caissons at the foundations of bridges or underground railways, sometimes on coming into the open air become paralyzed. It is usually a paralysis referable to the spinal cord, and usually of the legs; but there may be apoplectic attacks with hemiplegia, indicating that the brain is affected. The attack may be fatal, but recovery usually takes place.

There seems little doubt that the condition arises from the abnormal escape of gas from the blood-vessels of the cord. The person has been under a pressure of two or three atmospheres, and the gases of the blood accumulate. On returning to the ordinary atmosphere there is an excessive escape of gas. The cord being in a confined canal, and its tissue being soft, pressure is exercised on the nerve tissue, and there may even be some tearing of the tissue. There is rarely haemorrhage. The injury to the cord may induce a subsequent inflammation, the spaces formed by the gases becoming occupied by round cells.

Literature

Pott, Palsy from curvature of spine, 1776 and 1782; Brodie, Injuries of the spine, 1837; Jaccoud, Des Paraplegies, 1864; Frommann, Normal und path. Anat. des Riickenmarks, 1867; Feinberg, (Myelitis) Virch. Arch., lix., 1874; Snell, Caisson disease. Lond., 1896. For more complete literature see Ross, ii., 89.