Microneurographie

Microneurography is a neurophysiological method employed to visualize and record the traffic of nerve impulses that are conducted in peripheral nerves of waking human subjects. It can also be used in animal recordings. The method has been successfully employed to reveal functional properties of a number of neural systems, e.g. sensory systems related to touch, pain, and muscle sense as well as sympathetic activity controlling the constriction state of blood vessels. To study nerve impulses of an identified nerve, a fine tungsten needle microelectrode is inserted into the nerve and connected to a high input impedance differential amplifier. The exact position of the electrode tip within the nerve is then adjusted in minute steps until the electrode discriminates nerve impulses of interest. A unique feature and a significant strength of the microneurography method is that subjects are fully awake and able to cooperate in tests requiring mental attention, while impulses in a representative nerve fibre or set of nerve fibres are recorded, e.g. when cutaneous sense organs are stimulated or subjects perform voluntary precision movements. Before the microneurography technique was developed in the late 1960s, impulses in peripheral nerves had been recorded in animal experiments alone using a technique that involved dissection and splitting the nerve. This approach is not tolerable for general use in humans although it has been pursued in one single study. Actually, the concern of nerve damage was a major obstacle for the development of microneurography because the approach of inserting a needle electrode in a human nerve was generally regarded as potentially dangerous and involving substantial risk of permanent nerve damage. The two Swedish scientists who developed the microneuropgraphy technique (Hagbarth and Vallbo) handled the medical-ethical concern by performing a large series of experiments on their own nerves during a period of about 2 years while carefully checking for nerve damage.