NEUROPHYSIOLOGICAL AND MORPHOLOGICAL ASPE CTS OF NERVE-CONDUCTION .2.SPECIFIC FINDINGS IN COMMON NEUROPATHIES

There is a strong correlation between structural and neurophysiologica l findings in a wide variety of neuropathies if appropriate sets of di agnostic procedures are employed. Etiologic considerations heavily rel y on the dissection of axonal damage and demyelination. Histologically , the work-up of a nerve biopsy should not only focus on transverse se ctions but should also include teased fibre studies and electron micro scopy. Particular emphasis should be put on axon-myelin junctions at p aranodal regions. Although critically involved in generating gross neu rophysiological nerve dysfunction in primary as well as secondary demy elination, paranodes have long been neglected by morphologists. Neurop hysiological studies in patients with neuropathy should be performed a s early as possible and repeated in the course of the disease. Routine nerve conduction techniques must be complemented by F-wave studies an d by a careful assessment of compound action potential amplitudes. Ser ial studies not only give a comprehensive view of the current status o f nerve function but also provide a valuable prognostic means. There a re some pitfalls, however: The diagnosis of nerve conduction block mus t not be made without taking innervation abnormalities into account an d without ensuring supramaximal stimulation. In the first two weeks of inflammatory neuropathies, a very distal conduction block has to be c onsidered if compound muscle action potential amplitudes are low in th e absence of denervation potentials in the electromyogram.