Phocomelia And Foreshortened (Telescoped) Phantom Limbs
Samuel A. Weiss, Ph.D.
An abridged form of this article was published in the Journal of the American Medical Association, March 23, 1963, Vol. 183, p. 1053.
Following traumatic or surgical amputation of a limb the illusion of its presence is often experienced, although the amputee knows it is gone. Some amputees experience a whole or continuous limb. Usually, the phantom limb has "gaps", Only the distal phantom parts, which have greater cortical representation on the Penfield-Boldrey homunculus1 - hands, feet or digits - are felt and the intervening portions are missing.2 The distal phantom is usually experienced (1) as of the same length as the missing limb in the appropriate anatomical location, i.e., extended; (2) as somewhat foreshortened, i.e., a retracted or partly telescoped phantom or (3) the digits may be felt within the stump or protruding from it - a completely telescoped phantom. (4) On rare occasions the phantom may be experienced as longer than the limb it represents.
The phenomenon of the telescoping or shrinking phantom has not been fully understood in the past.
Resemblance Between Phocomelia and the Shortened Phantom
Of interest is the resemblance of the foreshortened phantom limb to cases of phocomelia induced by ingestion of thalidomide or other causation.
In phocomelia some intermediate portions of the limb, the long bone(s), are absent. The distal hand or foot (complete or incomplete) is thus located closer to the proximal joint. In relation to the type and extent of missing elements the condition may be classified as proximal, distal or complete phocomelia.3
In proximal phocomelia the proximal segment of the limb (humerus or femur) is absent; in distal phocomelia the radius and ulna, or tibia and fibula are absent; in complete phocomelia only the most distal portion of the limb, the hand or foot, is present (in part or whole) and is attached to the trunk (shoulder or hip). Partial phocomelias are also found where only portions of the long bones are missing and the limb is thereby shortened.
Similarly, in a foreshortened phantom, the mental image of the distal part, hand or foot, is felt nearer to the stump, i.e., is completely or partly telescoped.
Foreshortened phantom limbs in a position near the stump and analogous to proximal and distal phocomelia are shown on pages 13 and 14. These phantom limb drawings are stylized artistic renditions of the actual drawings made and described by amputees. Because of a dearth of amputees with shoulder and hip disarticulations, no drawings were available to illustrate phantoms analogous to complete phocomelia although phantom distal parts telescoped at shoulder and hip have been reported.
Upper Proximal-M.F. has no humerus or radius, but the ulna is present.
Lower Proximal-S.R. has no femur, but fibula and tibia are present.
Upper Distal-H.S.K. The radius and ulna are absent and the hypoplastic fingers are attached to the distal humerus.
Lower Distal-T.B. has no fibula or tibia. The left foot is attached to the thigh.
Right Shoulder-Disarticulation-J.T.D. experiences only phantom fingers, hand and forearm. The phantom hand is felt at approximately elbow level.
Right Above-Knee-H.G. usually experiences a shortened phantom limb with the foot, ankle and part of the shank located at the end of the above-knee stump.
Right Above-Elbow-F.B. has a long above-elbow stump, almost an elbow-disarticulation. He experiences only his phantom fingers and palm which are felt at the distal stump.
Right Above-Knee-C.S. experiences only phantom toes and feet. Usually they are extended but occasionally these distal parts are felt at knee level
The upper extremities are more affected by phocomelia than the lower extremities.4,5,6 Similarly, the upper extremity amputations, as a group, especially the above-elbow amputation, are characterized by a greater proportion of shortened phantom limbs than the lower extremities.7
3. Developmental Factors
The cephalo-caudad or proximo-distad principle of development underlies embryo-logical growth and is apparently related to both phocomelia and the telescoped phantom. This principle states "that physical growth, especially embryological growth, tends to begin in the head end and progress toward the tail end. The principle is usually generalized to include also the tendency of growth to proceed from shoulder and thigh toward fingers and toes (proximo-distad development), (Synonym: Anterior-Posterior Development; Law of Developmental Direction)"8
In phocomelia arising from the ingestion of thalidomide during the critical developmental period, from the fourth through the sixth week, the drug apparently retards the development of the limb buds so as to cause an almost complete arrest in the growth of the long bones of the arms and legs, resulting in the flipper-like condition known as "phocomelia".
The proximo-distad gradient seems to be related to both thalidomide-induced phocomelia and the foreshortened phantom. The upper extremities are higher on the proximo-distad gradient and may therefore be more prone to phocomelia than the lower extremities. The malformations reveal that thalidomide arrests those developmental processes that are in progress when the embryo is exposed to the drug during the critical period. The arm buds develop slightly earlier than those of the legs. This may account for the greater frequency of arm damage. In cases where the lower extremities are affected, the arms are usually also involved. They are often affected more extensively, sometimes by amelia - total absence of the limb. The hand, developing after the arm and forearm, and the foot, developing after the thigh and leg, may therefore appear after the critical period and grow on the shortened intercalary parts. As mentioned, the distal parts also have greater cortical representation.
Similarly, the proximo-distad gradient (among other factors)' also influences the length of the phantom limb. The above-elbow stump, high on the gradient, has been shown to be more sensitive than the below-elbow, above-knee and below-knee stumps. Strong stump cues may tend to influence the amputee to perceive the phantom image of the distal part at, or nearer, to the stump. The above-elbow amputation may therefore be characterized by a greater proportion of foreshortened phantom limbs than the other amputation types.
Phocomelia is thus a state of arrested proximo-distad development in which the distal hand or foot does not progress as extensively from its proximal position as normally occurs.
It is proposed that foreshortening of the phantom limb is a regression to an earlier state of embryological growth in which the phantom distal hand or foot, in "ghost" form, resumes, under certain conditions, the embryological position it once had as a natural limb and the hand or foot becomes smaller in size. The telescoped limb which has always seemed so puzzling is thus not a totally new, post-amputation phenomenon, for it has its basis in developmental growth factors. In phocomelia the natural distal limb never progresses from its proximal position. In telescoping of the phantom the image of the distal part regresses to an earlier embryological position.
The occasional experience of the phantom as totally within the stump (found mainly in the more sensitive upper-extremity amputation group, which is higher on the gradient) is reminiscent of the embryological state of the hand before it emerges from the arm buds.
In children, cases have been reported in which anomalous arm elements have been found completely encased within the shoulder. No photographs of these cases were available but the analogous situation in phantom limb cases is illustrated by G.L., a double amputee (left shoulder-disarticulation and left above-knee). Both phantom limbs are experienced totally within the shoulder and thigh respectively. The upper extremity phantom is depicted in Fig. 5 . The phantom of G.L.'s complete hand is felt within the flesh pad at the shoulder.
Curiously, with the long-term ingestion of thalidomide by adults, a new form of polyneuritis appeared. This neuropathy affects the upper-extremities more than the lower-extremities.9Among other symptoms, the condition is associated with tingling of the hands,4 reminiscent of the tingling sensation common in, if not indigenous to, the sensation of the painless phantom limb.
Phocomelia and foreshortened (telescoped) phantom limbs have elements in common.
The distal hand or foot (in part or whole) of both natural and phantom limbs are in a position closer to the joint, with the intermediate parts foreshortened or absent.
In both phenomena, upper-extremities are more often affected.
3. Developmental Factors
The cephalo-caudad or proximo-distad principle of development underlying embryological growth is apparently related to both phenomena.
It is suggested that as phocomelia is a state of arrested proximo-distad development, a foreshortened phantom is a regression to an earlier state of embryological growth in which the phantom distal part, which has greater cortical representation, resumes in "ghost" form the embryological position it once had as a natural limb. A telescoped phantom is thus not a totally "new" phenomenon in ontogenetic development.
The author appreciates the encouragement and suggestions of Hector W. Kay, Associate Project Director of New York University-Child Prosthetic Studies, and the assistance of Robert L. Burtch, Assistant Project Director, and Miss Roslyn Schlansky in the selection of the photographs; Jose Rodriguez-CoIon who executed the fine drawings of the phantom limbs and Herbert Bursky who helped in the technical work. Dr. Maurice Schweizer, Staff Librarian, provided invaluable assistance.
The encouragement of Dr. Sidney Fishman, Project Director, is also appreciated.
Samuel Weiss is Associate Project Coordinator, Amputee Psychology Research, New York University, New York, New York
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