SY7.2. Electrophysiological features in GBS and CIDP

Abstract

GBS is currently classified into axonal and demyelinating categories. Acute motor axonal neuropathy (AMAN), an axonal subtype of GBS, was widely recognized in the 1990s. Whereas in Europe and North America, acute inflammatory demyelinating polyneuropathy (AIDP) is considered the major subtype of GBS, in East Asia, and Central and South America, AMAN is found for 30–80% of GBS cases. Over the past 20 years, major advances have been made in understanding the immunopathogenesis and pathophysiology of AMAN. Clinically, AMAN is characterized by pure motor involvement, frequent antecedent Campylobacter jejuni enteritis, and serum anti-ganglioside antibodies. Electrophysiological studies frequently reveal, as well as axonal degeneration, rapidly reversible nerve conduction block/slowing (resolved within days to a few weeks); the time-course suggests functional or microstructural changes at the nodes of Ranvier. It is now established that disrupted nodal sodium channel clusters, and paranodal myelin detachment is responsible for conduction block in AMAN. CIDP is currently classified into “typical CIDP” and other variants such as “multifocal acquired demyelinating sensory and motor neuropathy (MADSAM)”. Typical CIDP is a classic form, clinically characterized by symmetric proximal and distal muscle weakness and motor- dominant manifestation. In typical CIDP, demyelination predominantly affects the distal nerve terminals and nerve roots, presumably because of the lack of the blood-nerve barrier in these regions, and this could be responsible for the “non-nerve length-dependent” distribution of muscle weakness. These findings suggest an importance of humoral immunity in typical CIDP. In contrast, MADSAM is characterized by multifocal demyelination in the intermediate nerve trunks. In MADSAM neuropathy, cellular immunity may be predominantly involved in breakdown of the blood-nerve barrier at the site of conduction block. Among the CIDP spectrum, typical CIDP and MADSAM are the major subtypes, and their pathophysiology appears to be distinct. The understanding of the pathophysiology of each CIDP subtype is important for appropriate immune treatments.