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Painful polyneuropathy is a debilitating neurologic problem and
frequently a challenging therapeutic management issue. Difficulties
in managing patients are too often the result of poor understanding
of their problem on the part of the treating physician. Many physicians
assume that there is no need to work up neuropathy because the final
outcome is likely to be an idiopathic, axonal disorder for which
there is no effective therapy. In fact, many neuropathies are responsive
to immunosuppressive therapies. Although responses to such therapy
constitute the minority, they should be vigorously sought before
telling patients there is no treatment for their progressive disorder.
In many cases, treatment of the polyneuropathy also leads to improved
pain control; however, pain is often a primary issue in and of itself
and must be treated irrespective of the potential for improvement
of the underlying polyneuropathy. In these cases, pain management
specialists may work in concert with neurologists to provide a comprehensive
treatment approach.
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Clinical Issues
in Polyneuropathy: Introduction
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The first step in developing a rational approach to patient management
is obtaining a working knowledge of the underlying disorders that
fall under the category of neuropathy. Although it is often used
loosely to refer to polyneuropathy, the term neuropathy is actually
not specific and implies any peripheral nerve lesion, focal or diffuse.
Classification schemes used widely among peripheral neurologists
are based on anatomic and physiologic characteristics of the various
disorders affecting peripheral nerves. The use of these classifications
is not just an academic exercise but creates a basis for rational
decision making in the evaluation and management of patients. The workup
and treatment of individual patients with neuropathy must be approached
with a basic understanding of the clinical behavior, including the
anatomic and pathophysiologic characteristics, of the various neuropathic
disorders.
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Classification
and Clinical Course
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The term polyneuropathy is used to describe a condition that
is fairly symmetric and generalized, as opposed to focal neuropathy
(mononeuropathy) or multifocal neuropathy (mononeuropathy multiplex).
This chapter focuses on the diffuse disorders, including polyneuropathy
and multifocal mononeuropathies. These two groups of disorders may
be indistinguishable clinically and are frequently accompanied by
severe and disabling pain.
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Once a disorder of peripheral nerves is suspected, an attempt
should be made to characterize the clinical features based on the
time course, anatomic distribution, and physiology. Using this information,
a reasonable differential diagnosis can be developed, which will
determine appropriate further workup and management. This section
further discusses the clinical and physiologic features of the diffuse
neuropathies; their diagnostic evaluation is covered in the next
section.
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An important clue as to the etiology of a particular polyneuropathy
(PN) is its time course. Generally accepted guidelines would classify
a neuropathy as acute (< 3 weeks), subacute (weeks
to months), or chronic (> 4–6 months).
Notably, neuropathies in each of these categories may be associated ...