From the Archives
Phantom limbs and body shape (Being the Presidential Address, Neurological Section, Royal Society of Medicine, 1941). By George Riddoch. Brain 1941; 64: 197–222.‘Knowledge of the persistence, as a phantom, of a limb which has been removed ... must have been mysterious to our forefathers, whose physiological and psychological advantages were less than our own ... it would not be surprising if the unfortunate patient was regarded as an obstinate, lying fellow or possessed of the devil ... it was a matter that was best left alone’. Dr Riddoch goes on to present a sympathetic analysis of the reticence that the modern patient still displays in confronting something so strange: ‘dread of the unusual, of disbelief, or even the accusation of insanity’. In contrast to the phantom-illusion disorders of body image that accompany insanity and hysteria—in that context, the outcome of gross mental disturbance—those that follow a lesion of the sensory pathways, with or without amputation of the limb, must arise from disordered physiological processes. So, what are these?
A Methodist parson ‘of somewhat rigid and unimaginative outlook’ had a below-knee amputation at age 14, following which he remained aware of his former hallux and instep but not the intermediate parts. This ‘foot’ fits the contours of his artificial limb, moves with it, can be voluntarily flexed and extended, and experiences different sensations when placed on subtly different terrains. The phantom tingles with the rest of his body during excitement (to which, evidently, he is not much disposed), and can be ignored. It is not painful, though feels too wide and is occasionally uncomfortable. The phantom acts as a barometer, nicely anticipating a change in the weather. Manipulating a small sciatic stump neuroma reproduces a few of these sensations. With the prosthesis removed, he happily crosses his ‘legs’ and sometimes suffers through setting off on the missing limb when rising, legless, from a chair. Thus, our man of the cloth lives comfortably with his phantom, but is unusual in that everything persists 34 years after having lost his left lower leg.
More generally, it is usual for the early experience of a fore-shortened but peripherally represented phantom gradually to extend into the extremity of the prosthesis and fade with time. The phantom may have autonomic activities such as sweating. When present, the former hand or foot can be made to pass through solid objects, as imaginary movements negotiate apparent obstacles in its path. The phantom may elicit mirror movements in the intact limb, as described by Jean-Martin Charcot (Lécons du Mardi. June 18th, 1888: 447–460: in translation, courtesy of Jean-Claude Baron, ‘M. Charcot: Have you not told me before that your fingers on occasions will move outside your control? The patient: Yes, sir, this is correct: on stormy days the fingers move, open and close; and occasionally I feel as if a lancet was stabbing inside the thumb and the palm of my hand ... I always feel it is here, but for quite a while it has tended to get nearer the stump. M. Charcot: Do you dream that you are in full possession of your hand? The patient: When I dream, I have got my hand as always. I often dream that I am still controlling tickets in the train. M. Charcot: I have already told you about the psychophysiological influence of movements executed by one of his hands on the movement executed by the other hand. ...’). In bilateral amputees, both or one only of the missing limbs may develop phantom phenomena, with unpredictable distributions of pain and stump tenderness. Phantom sensations are never normal. Rather, they are invariably perverted in size, position and range of movement; and the risk of discomfort—often excruciating pain—is always present.
In the 50% of patients experiencing pain after traumatic or surgical amputation—more usually of the arm than the leg—the entire missing limb, not just its extremity, feels unpleasant. The character of the pain matches the distribution of pre-amputation symptoms, or the circumstances under which the loss occurred: ‘a soldier whose right arm was blown off by the premature explosion of a bomb, which he had been holding, felt as if his painful phantom hand were still grasping the bomb and he could not alter its position’. High amputations produce a shortened phantom, and with a tendency for less severe pain that may increase temporarily with elongation, as in wearing an artificial limb; even then, the phantom foot still stops short of the true but artificial extremity. ‘The presence of painful or uncomfortable sensations leads to persistence of the phantom ... and ... limitation of ... movement ... from voluntary effort. On the other hand (Riddoch's little joke, perhaps), involuntary movements are more common in painful phantom hands and feet, as well of the stump’. The quality of pain is constricting. The thumb and fingers seem tightly flexed and with the nails cutting into the palm. Phantom movement increases the agony. Furthermore, as if these background sensations are not enough, showers of intense neuralgic paroxysms, provoked by manipulation of the stump and unrelated movements (such as yawning, micturition or defecation) or changes in emotional state, evoke a sensation as if the absent fingers and toes are being torn off. Other appendages—breasts and noses—may ‘phantomize’ after amputation. And Dr Riddoch cannot resist mentioning that Silas Weir Mitchell knew of a soldier from the American Civil War in whom a phantom penis experienced tumescence of the disconnected glans in response to vascular alterations occurring at the stump (Injuries of nerves and their consequences, 1872: in fact, this was an anecdote related to Weir Mitchell by Dr Ruschenberger of the US Navy; see footnote to page 350). In all these situations, ‘the unfortunate sufferer is not only a prey to the ordinary disturbances of everyday life but is continually fearful of their occurrence’ (Fig. 1).
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But what can be done? Attention to the stump through prevention of neuromas, avoidance of sepsis, management of local temperature and posture, and containment of involuntary movements all act to suppress the discomfort. When present, these adverse features are bound together in painful harmony to produce the worst imaginable examples of painful phantom limb. William Kenneth Livingston had already shown that chemical sympathectomy may help (Livingston WK. Fantom limb pain. Archives of Surgery 1938: 37; 353–370). At this point, Dr Riddoch adopts the stance of the clinical scientist steeped in the observations made by Henry Head, Gordon Holmes and himself during and after the Great War. He explores therapeutic options, other than stump management, and addresses the more general issue of altered perception of body parts—seeking a pathophysiological synthesis of this devilish complaint. Denervating the phantom by nerve or root section merely detaches the persistent pain from movements of the phantom: lateral rhizotomy renders the phantom painless but still present and linked to its own movements; only a lesion of the contralateral cerebral cortex removes the phantom, in all respects. As Head and Holmes had already described, ‘a man who had a painless phantom left foot following amputation of his leg, some time later sustained extensive injury to his right parietal cortex, with consequent loss of postural sensibility in his left upper and lower limbs, and from that moment his phantom foot disappeared’ (Head H and Holmes G. Sensory disturbances from cerebral lesions. Brain 1911: 34; 102–254).
Dr Riddoch extends his analysis to cases in which lesions of sensory pathways produce phantom impressions of limbs that are not missing, the percept sometimes exactly overlapping the genuine article but dissociable from it by suitable manipulation. Rarely, these may occur with lesions of peripheral nerves or spinal roots, and the brachial, although seldom the lumbar, plexus. Thus, a boy of 18 avulsed his brachial plexus and had no movement or sensation below the elbow, yet experienced painful phantom sensations and movements of that arm that did not track passive displacement of the real limb; these persisted after that arm was indeed amputated, the phantom sensations and movements again becoming yoked as postural sensibility returned to the stump. As Riddoch had observed in the Great War, with the return of reflex activity, complete division of the spinal cord leads to a phantom awareness of flexion, anticipating the future posture of the paralysed limbs, which are, at this early stage, still extended. And the same may occur after partial cord damage, as in the patient with herpes zoster myelitis who, in the context of a Brown-Sequard pattern of sensory loss, felt his left leg to be flexed and passing through the bed to the floor when sitting. Later, with the return of postural sensibility, the phantom resumed the true position of his paralysed limb. Although not personally encountered, Dr Riddoch is aware of thalamic lesions associated with nasty phantom sensations of crushing and twisting of the paretic limb that could often be settled by touching or looking at the stationary and appropriately positioned paralysed arm. He describes three examples of focal sensory epilepsy in which the experience was of duplication, missing sections and replacement of the real limb by a phantom.
So what has George Riddoch learned from his clinical and therapeutic analyses? He starts by considering the physiological properties of body image. The acquisition of this sense determines motor skills for sport and action. Variations in its sophistication are regulated by developmental processes that make for inter-individual differences akin to variations in intelligence; and ‘no part of the body in action is ever independent of the whole ... every movement is accompanied by adjustments of a neighbouring segment and ... of the whole body’. But what delivers the impressions of body image to the cortex? This sense is dependent on postural sensibility, whereas touch, pain and temperature serve to locate the sensory functions involved in the control of movement and postural reactions. Changes in outline of the body and postural variations are measured by ‘schema or plastic models’. Quoting Head and Holmes (1911), ‘by means of ... alterations in position we are always building up a new model of ourselves which constantly changes ... activity of the cortex brings every fresh group of sensations evoked by altered posture into relation with ... plastic models of body shape ... constructed through the process of ... impressions which arise from stimulation of the surface of the body’. Against this background, and in seeking explanations for the many features of phantom percepts of body image, George Riddoch suggests that stimulation of the stump and its intact postural sense act to preserve awareness but only for those sections of the missing limb that normally dominate the cortical map. Thus, phantom symptoms affect structures with which the ‘homunculus’ is richly endowed. As the nerve heals, local stimulations settle and the phantom disappears into the stump. But everything is different in an unhealthy stump where interstitial neuritis may persist in the severed nerve: demonic phantom phenomena then evolve, the distal fore-shortened painful phantom telescoping out to the periphery until such time as pain is relieved by attention to the stump, or relief is provided by lateral chordotomy. De-afferentation, by dorsal root section, merely removes postural sense and so detaches perceived localization of the pain from retained movements of the stump: ‘the outline model of the phantom part remains ... (and) is still placed in relation to the body ... and when the whole body is moved the phantom moves with it ... (but) it is as if it were suspended in mid-air, in part a foreign body which cannot be got rid of’. This ‘surface-shape model’ explains the phantom experiences of brachial plexus and partial spinal cord injury resulting in a denervated but preserved limb: accounts for why the phantom strays from the real part with loss of postural sensibility but intact surface sensations; and provides an explanation for the loss of all phantom experiences following an appropriately placed cortical lesion that removes both discriminative and cutaneous sensations.
On phantom movement, Riddoch has less to say. Associated movements are nothing more than vigorous postural reactions resulting in movement of the intact opposite limb attributable to ‘intimate linkage of the postural model of one limb with that of its fellow’. In short, ‘(phantom) movement is initiated from the cortex, but for it to be possible the postural-movement model of the limb must be intact, which necessitates preservation of postural sensibility in the stump’. The maverick properties of phantoms with respect to their appearance, occurrence and disappearance relate to the interplay of peripheral stimulation, even when interstitial neuritis appears to have settled, and central inhibition. The latter can never overrule intense stimulation from the stump, even though, under favourable circumstances, cortical ‘adaptability’ may modulate various features of the phantom limb, permanently or until an alteration in health or emotion allows the symptoms briefly to re-engage. Finally, George Riddoch waxes philosophical. The ability of the amputee to elongate his missing limb into the inanimate prosthesis is not different, in principle, ‘from the surgeon who projects his fingers to the end of the probe, or that of the edentulous who incorporates his false teeth ... the trained motorist (who) identifies his car with himself, the airman with his machine and the angler with his fly at the end of a long line’—in the view of Samuel Butler, tools as detachable limbs distinguishing man from lower animals (Erewhon Revisited, 1901). Individuals differ in their ability to adopt this aptitude for projection through tools, for reasons that are inborn and honed through training. But such skills are bound to be inhibited if contact of the tool with the body evokes discomfort or pain. ‘It is another illustration of the dominance of pain over adaptive functions’.
In returning to changes in properties of the cortex and distal stump that affect the interplay of pain, perception, placement and plasticity in amputees, Karen Reilly and Catherine Mercier (pages 2211 and 2202) and their associates take on the mantle of George Riddoch, elucidating the physiological basis for these phenomena and thereby adding significantly to the body of works that now makes up ‘the opera of the phantom’.
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