What is Clinical Neurophysiology?


The clinical neurophysiologic examination is an extension of a neurologic consultation, not just a set of laboratory tests. It does not only verify or exclude a clinical suspicion but also gives precise definition of site, type and degree of lesion and reveal abnormalities that are clinically uncertain, silent or unsuspected.



In US and in many European countries the EMG and EEG laboratories often are linked to neurology or physical medicine and rehabilitation and the laboratories are run by doctors with clinical responsibilities. However, in the Scandinavian countries and Great Britain, the departments of clinical neurophysiology are usually independent laboratores run by specialists in CN. This separation from patient care has the advantage of allowing high degree of specialisation and specific research in the field. It may have the disadvantage that the clinical neurophysiologist looses the clinical feedback. In many places this has been compensated by frequent rounds with referring clinicians. In Sweden CN is an independent specialty since late 50ties. It is established at each university and only the specialits in these institutions are performing EMG, EEG, evoked potentials and neuro-monitoring. Training for the specialty includes 4 years in clinical neurophysiology and 0.5 year in neurology. A similar training is available in Norway, Finland, Denmark and Great Britain.


In general, the neurophysiologic methods describe and quantify functions and pathophysiologic changes in central and peripheral nervous system. They reflect, but do not measure directly biochemical or morphologic aspects of central or peripheral nervous system. This distinction to other methods and measurements should be made clear. Adequate techniques should be applied for each specific question.

Within neurophysiology there is continous development of new sophisticated methods for understanding of pathophysiologic mechanisms. EMG (electromyography) describes functional status of central and peripheral nervous systems and is complementary to other techniques for evaluation of the neurologic patient. Various categories of morphologic and physiologic changes are seen in the motor unit in most nerve-muscle disorders. They are either acute, often functional in nature or slowly developing with morphologic correlates. These changes provide help in the assessment of a diagnosis or in testing the short term effect of drugs and the latter may also be used to monitor changes in a disease or response to therapy. The morphologic changes may be related to severity of the disease or to repairative processes. Therefore, some of them are inversely correlated to the clinical picture e.g. high degree of reinnervation may produce a good compensation for functional defecit which then may be difficult to detect..

The EEG method (electroencephalography) involves the recording of the weak currents from the cerebral cortex with surface electrodes mounted on the scalp of the patient, thus monitoring the functional status of the brain. The main indication for the EEG investigation is the suspicion of epileptic seizures, however, the method will show any dysfunction in the brain that involves the signalprocessing in the neuronal network changing the electric activity in the brain cortex. The transformation from analog recordings with paper printers to digital recordings with the signal displayed on a screen and data sampled on to a hard disc has given the possibilities of quantitativa analysis of the brain activity. There are also new methods wich allows a source localisation of electric activity in the brain (dipole analysis) which combined with structural neuroimaging (MRI) gives quite new information on normal brain function as well as pathology.