Undiagnosed neuropathies: the impact of ancillary investigations.

Before the advances in knowledge about peripheral nerve disorders that have accumulated over the past two to three decades, a high proportion of chronic neuropathies seen in tertiary referral centres remained undiagnosed. With intensive investigation, it is now possible to reduce this proportion to 13-14%. The category for which an aetiological diagnosis is most elusive is that of chronic axonal polyneuropathies, although some multifocal neuropathies resist explanation. An aetiological diagnosis is achieved for most demyelinating neuropathies. Some examples of chronic idiopathic axonal polyneuropathy (CIAP) may be of genetic origin; others may have an autoimmune basis. Advances in the molecular genetics and immunopathology of peripheral nerve disorders are likely to lead to the elucidation of some of those neuropathies that currently have to be classified as cryptogenic.