A fundamental distinction can be made between what man receives from his sense organs and how he feels about it. Such separation of sensation from evaluation is not always clearly recognized. Confusion of the two processes is notably evident in what has been written of a rare congenital disorder in the perception of pain. The affected individuals are not an entirely homogeneous group, for some report occasional experiences as painful, and, in a few, other modalities of sensation are impaired, although rarely to a significant degree. The central and still perplexing feature in all, however, is a denial of pain from all conventional forms of noxious stimulation.
Physicians who have studied subjects with this curious anomaly have not agreed upon its nature. Of 24 reports in the past two decades, some very recent, in 10 the defect is described as "insensitivity" to pain, in 13 as "indifference" to pain, and
Kunkle EC. Pain Unfelt or Pain Unheeded A Distinction with a Difference. Arch Neurol. 1961;5(6):579. doi:10.1001/archneur.1961.00450180001001