Pathophysiology of conduction block in neuromuscular diseases

Polarization of axonal membrane is necessary for impulse conduction in peripheral nerve fibres. Smooth functioning of ion channels is responsible for proper excitability of axonal membrane. Myelinated fibres allow for differentiating various regions of one segment, i.e. nodal, paranodal, juxtaparanodal and internodal. Among the most frequent sodium channels, there are 3 types with the highest occurrence in the nodal region. Potassium channels can be divided into 3 voltage-operated subtypes. Appearance of fast K+ channels is limited to juxtaparanodal segment. Testing of ion channels and membrane excitability is possible with the use of double-stimulation technique or with the threshold electrotonus assessment. Conduction block can be divided into,activity dependent" and,activity independent". We present patients with chronic demyelinating polyneuritis, multifocal motor neuropathy and compressive mononeuropathy as clinical case reports.