This temporal delay allows patients some degree of function during the day when they can move limbs away from surfaces after a time, before evocation starts to occur. Sleeping is another matter, since contact with bed sheets persists when asleep, causing a periodic waking in a flaming hell of evoked pain on nights when the sedation fails. Long provoked evoked pain is approximately equivalent to having been scrubbed for hours with a wire brush. The patient often fears these events, almost to the point of psychological devastation. Significantly, both spontaneous and evoked pain are always worst on areas of the body where sensory deficit is greatest.
Evoked pain is also very durable, lasting as long as a half hour after the light touch is stopped.
It decreases around twenty-five percent as soon as the stimulus is removed, and then gradually diminishes back to the ground level spontaneous pain. The rate of disappearance can be accelerated by bringing the skin temperature to the window of greatest comfort. Because central pain originates centrally, the pain is felt over a large part of the body surface, sometimes the entire body. The psychological implications of this are simple. The implications psychologically of pain over large body surfaces are well known from burn patients.