Copyright © 1999 Massachusetts Institute of Technology
Phantom limbs occur in 95 to 100 percent of amputees who lose an arm or leg. The phantom is usually described as having a tingling feeling and a definite shape that resembles the somatosensory experience of the physical limb before amputation. It is reported to move through space in much the same way as the normal limb would move when the person walks, sits down, or stretches out on a bed. At first, the phantom limb feels perfectly normal in size and shape -- so much so that the amputee may reach out for objects with the phantom hand, or try to step onto the floor with the phantom leg. As time passes, however, the phantom limb begins to change shape. The arm or leg becomes less distinct and may fade away altogether, so that the phantom hand or foot seems to be hanging in midair. Sometimes, the limb is slowly "telescoped" into the stump until only the hand or foot remains at the stump tip.
Amputation is not essential to the occurrence of a phantom. After avulsion of the brachial plexus of the arm, without injury to the arm itself, most patients report a phantom arm that is usually extremely painful. Even nerve destruction is not necessary. About 95 percent of patients who receive an anesthetic block of the brachial plexus for surgery of the arm report a vivid phantom, usually at the side or over the chest, which is unrelated to the position of the real arm when the eyes are closed but "jumps" into it when the patient looks at the arm. Similarly, a spinal anesthetic block of the lower body produces reports of phantom legs in most patients, and total section of the spinal cord at thoracic levels leads to reports of a phantom body, including genitalia and many other body parts, in virtually all patients.
The most astonishing feature of the phantom limb is its "reality" to the amputee, which is enhanced by wearing an artificial arm or leg; the prosthesis feels real, "fleshed out." Amputees in whom the phantom leg has begun to "telescope" into the stump, so that the foot is felt to be above floor level, report that the phantom fills the artificial leg when it is strapped on and the phantom foot now occupies the space of the artificial foot in its shoe. The reality of the phantom is reinforced by the experience of details of the limb before amputation. For example, the person may feel a painful bunion that had been on the foot or even a tight ring on a phantom finger.
Phantoms of other body parts feel just as real as limbs do. Heusner describes two men who underwent amputation of the penis. One of them, during a four-year period, was intermittently aware of a painless but always erect phantom penis. The other man had severe PAIN of the phantom penis. Phantom bladders and rectums have the same quality of reality. The bladder may feel so real that patients, after a bladder removal, sometimes complain of a full bladder and even report that they are urinating. Patients with a phantom rectum may actually feel that they are passing gas or feces. Menstrual cramps may continue to be felt after a hysterectomy. A painless phantom breast, in which the nipple is the most vivid part, is reported by about 25 percent of women after a mastectomy and 13 percent feel pain in the phantom.
The reality of the phantom body is evident in paraplegic patients who suffer a complete break of the spinal cord. Even though they have no somatic sensation or voluntary movement below the level of the break, they often report that they still feel their legs and lower body. The phantom appears to inhabit the body when the person's eyes are open and usually moves coordinately with visually perceived movements of the body. Initially, patients may realize the dissociation between the two when they see their legs stretched out on the road after an accident yet feel them to be over the chest or head. Later, the phantom becomes coordinate with the body, and dissociation is rare.
Descriptions given by amputees and paraplegic patients indicate the range of qualities of experience of phantom body parts. Touch, pressure, warmth, cold, and many kinds of pain are common. There are also feelings of itch, tickle, wetness, sweatiness, and tactile texture. Even the experience of fatigue due to movement of the phantom limb is reported. Furthermore, male paraplegics with total spinal sections report feeling erections, and paraplegic women describe sexual sensations in the perineal area. Both describe feelings of pleasure, including orgasms.
A further striking feature of the phantom limb or any other body part, including half of the body in many paraplegics, is that it is perceived as an integral part of one's SELF. Even when a phantom foot dangles "in midair" (without a connecting leg) a few inches below the stump, it still moves appropriately with the other limbs and is unmistakably felt to be part of one's body-self. The fact that the experience of "self" is subserved by specific brain mechanisms is demonstrated by the converse of a phantom limb -- the denial that a part of one's body belongs to one's self. Typically, the person, after a lesion of the right parietal lobe or any of several other brain areas, denies that a side of the body is part of himself.
There is convincing evidence that a substantial number of children who are born without all or part of a limb feel a vivid phantom of the missing part. The long-held belief that phantoms are experienced only when an amputation has occurred after the age of six or seven years is not true. Phantoms are experienced by about 20 percent of children who are born without all or part of a limb (congenital limb deficiency), and 20 percent of these children report pain in their phantom. Persons with congenital limb deficiency sometimes perceive a phantom for the first time after minor surgery or an injury of the stump when they are adults.
The innate neural substrate implied by these data does not mean that sensory experience is irrelevant. Learning obviously plays a role because persons' phantoms often assume the shape of the prosthesis, and persons with a deformed leg or a painful corn may report, after amputation, that the phantom is deformed or has a corn. That is, sensory inputs play an important role in the experience of the phantom limb. Heredity and environment clearly act together to produce the phenomena of phantom limbs.
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Copyright © 1999 Massachusetts Institute of Technology