Microelectrode Exploration of Human Nerves: Physiological and Clinical Implications 1

When Lord Adrian gave the Jackson Lecture in 1947he expressed the basic idea behind this lecture series by saying: 'We ought to try from time to time to survey our new knowledge with Jackson's example in mind, not so much in the pious attempt to make them fit his scheme but in the expectation that we shall learn something by so doing' (Adrian 1947). To have Jackson as an example implies a challenge not only to keep our eyes and minds open for new observations, but to constantly strive to understand the 'nature' of the phenomena ,we observe. According to Holmes (1954), Jackson was a scientist with a framework of 'ideas in good order' which helped him to 'discern the relevant and the significant in the welter of phenomena and processes that passed before his eyes'. He made his observations on man, not on experimental animals. He gained most of his insights by carefully observing and analysing the symptoms and signs in patients with different types of neural disorders, or in his own words: by observing 'the experiments disease makes on man' (Taylor 1931-32). Jackson would probably be impressed if he sawall the technical facilities we have today in our laboratories ofclinical neurophysiology, but it is questionable ifhe would be impressed by Our 'framework of ideas'. If he saw EEG recordings in epileptic patients he would with a glance of recognition and satisfaction observe the epileptic discharges which he predicted more than 100 years ago. But he would probably also start to ask questions about the 'nature' of epilepsy to which we have no answer. Confronted with an EMG machine he would be impressed by the fact that it is possible to see and to listen to the traffic of motor impulses by which the central nervous system controls the skeletal muscles, and he would with interest observe the abnormal EMG patterns in patients with 'destroying lesions'. But again he would probably raise a number of difficult questions to which we have no complete answers. He would, for example, like us to tell in some detail how coordinated, purposeful movements are generated by the brain and how they are modulated by the controlling afferent patterns which are set up as the act progresses. His interest might rise when he learns that today we can record the impulse messages by which muscle and skin receptors in man communicate with the central nervous system and that with the same technique, called microneurography, we can also envisage the traffic of impulses in vasoconstrictor and sudomotor nerve fibres. We should recall that Jackson's interest in motor control mechanisms was not limited to the control of skeletal muscles; it included also the autonomic control of arterial coats, muscle fibres of intestines, glands, etc. The work carried out by myself and my colleagues during the last decade is largely based on microneurography recordings in man, both in healthy subjects and in patients. My intention now is to give some examples of the type of information that this recording technique can provide concerning proprioceptive, exteroceptive and autonomic functions in man. The technique of microneurography, as developed by Vallbo and myself 15 years ago, is in principle quite simple. It is mainly a matter of handling and directing a percutaneously IDserted tungsten microelectrode in such a way that its uninsulated tip impales one of the fascicles in a peripheral nerve. During the searching procedure, the microelectrode is alternately used for recording, and electrical stimulation with brief pulses. When searching for