Conduction block--the diagnostic value in the early stage of Guillain-Barre syndrome.
Immune-mediated segmental demyelination is the basic pathomorphological substrate of the Guillain-Barre syndrome (GBS). The aim of the study is to determine the diagnostic value of the conduction block in the early stage of GBS, as well as its changes during of the development of the disease. Sixteen patients with GBS were examined. Electroneurography (motor nerve conduction studies) was performed at interval from the third day of the onset till the first year. Partial CB in the early stage of the disease (range 0-15 days) was registered in 81,2% of the patients. In demyelinating forms of GBS partial CB was determined in 61% of the investigated nerves. It is the most often observed in peroneal nerves, followed by tibial, ulnar and median nerves in the same order. The maximal reduction of the amplitude of the CMAP (maximal CB) was registered before the 30th day from the onset of the disease with following recovery on the sixth month and first year. Partial CB is more often observed in the early phase of GBS, when it could be the only sign of demyelination. When patients reached a clinical plateau, progressive slowing of motor nerve conduction and increasing CB were registered. Proximal CB was revealed more often than distal CB, because of the typical initial localization of the process. In the early phase of GBS, proximal CB is most often found in lower limbs (in peroneal nerve, followed by tibial nerve). In patients with axonal damage, CB was more severe than in demyelinating group. Partial CB is an important diagnostic criterion for segmental demyelination, which helps for confirming the diagnosis of early GBS, when conduction velocity and other electrodiagnostic criteria for demyelination are normal.