Clinical neurophysiology of demyelinating polyneuropathy

Demyelinating neuropathies are remarkably varied in their clinical characteristics: In etiology they may be inherited or acquired, in their time course, acute or chronic, and in their distribution, multifocal or generalized. They present with phenotypes that range from an indolent disorder that begins in childhood and progresses slowly over decades (as might be seen in an inherited form) and leads to weakness but preserved ambulation, to a neuropathy with fulminant onset and rapid progression culminating in tetraparesis and respiratory failure (as seen in the Guillain-Barre syndrome). Often demyelinating neuropathies are amenable to treatment that greatly reduces the burden of disease and extent of disability. Thus, electrophysiologic studies are critically important as an investigatory tool in the evaluation of patients with suspected demyelinating neuropathies. In this chapter, we focus our discussion on the manifold electrophysiologic details regarding the demyelinating neuropathies and provide the reader with the clinical context and pathophysiological underpinnings to help appreciate the complex character of these disorders, including the Guillain-Barré syndrome; chronic inflammatory demyelinating polyneuropathy and its variants; the dysimmune demyelinating neuropathies that accompany systemic disease such as paraproteinemia, POEMS syndrome, and multifocal motor neuropathy; diabetic neuropathy; the demyelinating inherited polyneuropathies, and the demyelinating neuropathy from toxic exposures.