Thus, Dr Jonathan Cole, a former student of mine and now a spinal neurophysiologist, describes how in a woman with persistent phantom leg pain, anaesthesia of the spinous ligament with Lignocaine caused the phantom to be anaesthetized (indeed to disappear) briefly; but that electrical stimulation of the spinal roots produced a sharp tingling pain in the phantom quite different from the dull one which was usually present; whilst stimulation of the spinal cord higher up reduced the phantom pain (personal communication). Dr Cole has also presented detailed electrophysiological studies of a patient with a sensory polyneuropathy of fourteen years’ duration, very similar in many respects to Christina, the “Disembodied Lady” (see Proceedings of the Physiological Society, February 1986, p. 5IP).
7. On the Level
It is nine years now since I met Mr MacGregor, in the neurology clinic of St. Dunstan’s, an old-people’s home where I once worked, but I remember him—I see him—as if it were yesterday.
‘What’s the problem?’ I asked, as he tilted in.
‘Problem? No problem—none that I know of . . . But others keep telling me I lean to the side: “You’re like the Leaning Tower of Pisa,” they say. “A bit more tilt, and you’ll topple right over.”’
‘But you don’t feel any tilt?’
‘I feel fine. I don’t know what they mean. How could I be tilted without knowing I was?’
‘It sounds a queer business,’ I agreed. ‘Let’s have a look. I’d like to see you stand and take a little stroll—just from here to that wall and back. I want to see for myself, and 1 want you to see too. We’ll take a videotape of you walking and play it right back.’
‘Suits me, Doc,’ he said, and, after a couple of lunges, stood up. What a fine old chap, I thought. Ninety-three—and he doesn’t look a day past seventy. Alert, bright as a button. Good for a hundred. And strong as a coal-heaver, even if he does have Parkinson’s disease. He was walking, now, confidently, swiftly, but canted over, improbably, a good twenty degrees, his centre of gravity way off to the left, maintaining his balance by the narrowest possible margin.
‘There!’ he said with a pleased smile. ‘See! No problems—I walked straight as a die.’
‘Did you, indeed, Mr MacGregor?’ I asked. ‘I want you to judge for yourself.’
I rewound the tape and played it back. He was profoundly shocked when he saw himself on the screen. His eyes bulged, his jaw dropped, and he muttered, ‘I’ll be damned!’ And then, ‘They’re right, I am over to one side. I see it here clear enough, but I’ve no sense of it. I don’t feel it.’
‘That’s it,’ I said. ‘That’s the heart of the problem.’
We have five senses in which we glory and which we recognise and celebrate, senses thar constitute the sensible world for us. But there are other senses—secret senses, sixth senses, if you will— equally vital, but unrecognised, and unlauded. These senses, unconscious, automatic, had to be discovered. Historically, indeed, their discovery came lare: what the Victorians vaguely called ‘muscle sense’—the awareness of the relative position of trunk and limbs, derived from receptors in the joints and tendons—was only really defined (and named ‘proprioception’) in the 1890s. And the complex mechanisms and controls by which our bodies are properly aligned and balanced in space—these have only been defined in our own century, and still hold many mysteries. Perhaps it will only be in this space age, with the paradoxical license and hazards of gravity-free life, that we will truly appreciate our inner ears, our vestibules and all the other obscure receptors and reflexes that govern our body orientation. For normal man, in normal situations, they simply do not exist.
Yet their absence can be quite conspicuous. If there is defective (or distorted) sensation in our overlooked secret senses, what we then experience is profoundly strange, an almost incommunicable equivalent to being blind or being deaf. If proprioception is completely knocked out, the body becomes, so to speak, blind and deaf to itself—and (as the meaning of the Latin root proprius hints) ceases to ‘own’ itself, to feel itself as itself (see Chapter Three, ‘The Disembodied Lady’).
The old man suddenly became intent, his brows knitted, his lips pursed. He stood motionless, in deep thought, presenting the picture that I love to see: a patient in the actual moment of discovery—half-appalled, half-amused—seeing for the first time exactly what is wrong and, in the same moment, exactly what there is to be done. This is the therapeutic moment.
‘Let me think, let me think,’ he murmured, half to himself, drawing his shaggy white brows down over his eyes and emphasising each point with his powerful, gnarled hands. ‘Let me think. You think with me—there must be an answer! I tilt to one side, and I can’t tell it, right? There should be some feeling, a clear signal, but it’s not there, right?’ He paused. ‘I used to be a carpenter,’ he said, his face lighting up. ‘We would always use a spirit level to tell whether a surface was level or not, or whether it was tilted from the vertical or not. Is there a sort of spirit level in the brain?’
I nodded.
‘Can it be knocked out by Parkinson’s disease?’
I nodded again.
‘Is this what has happened with me?’
I nodded a third time and said, ‘Yes. Yes. Yes.’
In speaking of such a spirit level, Mr MacGregor had hit on a fundamental analogy, a metaphor for an essential control system in the brain. Parts of the inner ear are indeed physically—literally—like levels; the labyrinth consists of semicircular canals containing liquid whose motion is continually monitored. But it was not these, as such, that were essentially at fault; rather, it was his ability to use his balance organs, in conjunction with the body’s sense of itself and with its visual picture of the world. Mr MacGregor’s homely symbol applies not just to the labyrinth but also to the complex integration of the three secret senses: the labyrinthine, the proprioceptive, and the visual. It is this synthesis that is impaired in Parkinsonism.
The most profound (and most practical) studies of such integrations—and of their singular disintegrations in Parkinsonism— were made by the late, great Purdon Martin and are to be found in his remarkable book The Basal Ganglia and Posture (originally published in 1967, but continually revised and expanded in the ensuing years; he was just completing a new edition when he died recently). Speaking of this integration, this integrator, in the brain, Purdon Martin writes ‘There must be some centre or “higher authority” in the brain . . . some “controller” we may say. This controller or higher authority must be informed of the state of stability or instability of the body.’
In the section on ‘tilting reactions’ Purdon Martin emphasises the threefold contribution to the maintenance of a stable and upright posture, and he notes how commonly its subtle balance is upset in Parkinsonism—how, in particular, ‘it is usual for the labyrinthine element to be lost before the proprioceptive and the visual’. This triple control system, he implies, is such that one sense, one control, can compensate for the others—not wholly (since the senses differ in their capabilities) but in part, at least, and to a useful degree. Visual reflexes and controls are perhaps the least important—normally. So long as our vestibular and proprioceptive systems are intact, we are perfectly stable with our eyes closed. We do not tilt or lean or fall over the moment we close our eyes. But the precariously balanced Parkinsonian may do so. (One often sees Parkinsonian patients sitting in the most grossly tilted positions, with no awareness that this is the case. But let a mirror be provided, so they can see their positions, and they instantly straighten up.)