Current Concepts In The Diagnosis And Treatment Of Peripheral Neuropathies

Alan R. Berger, M.D. and Michael Pulley, M.D., PhD.
Alan R. Berger, M.D. is Professor of Neurology, University of Florida Health Science
Center/Jacksonville and Chairman, Department of Neurology, Shands Jacksonville.
Michael Pulley, M.D., Ph.D. is Assistant Professor of Neurology, University of Florida
Health Science Center/Jacksonville and Director, EMG Laboratory, Shands Jacksonville.

The last decade has seen remarkable progress in understanding the pathogenesis and treatment of peripheral neuropathies (PNs). Despite these scientific advancements, determining the etiology and instituting effective treatment remains a difficult but achievable goal. Peripheral neuropathies differ in their underlying cause, pathology, severity of deficits, rate of progression, and prognosis. A PN may occur in isolation, herald an underlying medical illness, or be one of its many clinical manifestations. Since etiology dictates the type of treatment, it is inadequate to merely document that a patient has a PN without determining its underlying cause. Accurate diagnosis requires clues from the clinical history and exam, electrodiagnostic studies (EDx), and select laboratory tests. A recent report indicated that in greater than 75% of cases, the etiology of previously "unclassified PNs," was able to be determined after referral to a medical center specializing in neuromuscular disease.1 Decisions regarding whom, when, and how to treat depend not only on the underlying etiology, but the nature of the clinical deficits, their severity and rate of progression, and the overall medical condition of the patient. In addition to administering specific treatment aimed at retarding the progression or resolving the neuropathy, care should also be directed to pain management, orthotics, and improving gait stability. This article will briefly discuss the clinical description, laboratory features, and treatment options of a select group of PNs most likely to be encountered in routine clinical practice. The reader is referred to the references for more detailed descriptions of these and other PNs.2,3

Immune Mediated Neuropathies

Guillain-Barré Syndrome

Guillain-Barré syndrome (GBS) is a term once reserved for rapidly progressing PNs with predominant demyelinating pathology (acute inflammatory demyelinating polyneuropathy — AIDP). It is now believed that GBS is a spectrum of immune mediated, acute and subacute PNs with demyelinating, axonal, or mixed demyelinating/axonal pathology.4 The underlying pathology often determines the clinical severity and course. Improvement tends to be more rapid and complete in those cases with greater demyelinating than axonal pathology. GBS occurs at any age and has an annual incidence of 1-2/100,000. Two-thirds of patients have a premonitory illness, usually viral (cytomegalovirus, Epstein Barr virus, and HIV are most common). Myocplasma pneumoniae and Camplybacter jejuni are the most common non-viral pathogens. Documenting the nature of the preceding illness usually has little clinical value, except when GBS heralds HIV infection.

Different forms of GBS have now been described, largely defined by their clinical features and whether the underlying pathology is predominantly demyelinating or axonal. Included in this spectrum are the following: acute inflammatory demeylinating polyneuropathy (AIDP), acute motor axonal neuropathy (AMAN), acute motor sensory axonal neuropathy (AMSN), acute autonomic neuropathy (AAN), and the Miller-Fisher syndrome (ophthalmoplegia, ataxia, areflexia). AIDP and AMSN present in similar fashion, with rapidly progressive motor or sensorimotor deficits, in an ascending or multifocal pattern, diminished reflexes, and cranial nerve or respiratory deficits. AMAN tends to have more pronounced distal weakness with sparing of cranial nerves. These patients may have profound weakness and clear axonal pathology on electrodiagnostic studies. Many patients with GBS initially present with vague, poorly demarcated sensory symptoms, prior to the onset of weakness. These patients are often misdiagnosed, sent home from the emergency department or office, only to return later with significant weakness. Although the classic description of GBS is of ascending sensorimotor deficits, less than 50% of GBS patients actually present in this manner. Cases with initial multifocal or proximal clinical deficits are often diagnostically confusing. Differential diagnosis includes brainstem infarctions, spinal cord compression, transverse myelitis, critical illness polyneuropathy, and hypokalemia. The following clinical items should be kept in mind when considering a diagnosis of GBS:

  1. Quadriplegia without facial weakness is unusual with GBS.
  2. A hanging jaw suggests a diagnosis of myasthenia gravis rather than GBS.
  3. Weakness of muscles supplied by upper cervical roots and oropharyngeal dysfunction is highly associated with subsequent respiratory distress.
  4. Early urinary retention occurs and can mimic spinal cord disease.
  5. Deep tendon reflexes (DTRs) can be unaffected distally if sensory loss and weakness is mainly proximal.

Regional variants in which the distribution of clinical deficits is restricted have been reported to occur in about 15% of GBS cases. Their recognition is important because they may simulate other diseases, thereby delaying the diagnosis of GBS. The most common variant is the Miller-Fisher syndrome, seen in 5% of GBS cases. Its predominant deficits of ophthalmoplegia, areflexia, and ataxia often mistakenly suggest brainstem infarction. Miller-Fisher syndrome may evolve into typical GBS with generalized sensorimotor deficits. Elevated antibody titers to GQ1b, a ganglioside found in high concentration in extraocular nerves has been reported.5 Other regional variants include the pharyngeal-cervical-brachial variant, bilateral VI nerve palsies, a paraparetic form mimicking a cauda equina lesion, and a predominant ataxic form.

There is some indication that prognosis in GBS is directly related to the rate of progression of weakness, the degree of axonal degeneration, and the age of the patient. Predominant axonal, rather than demyelinating pathology has been reported with prior CMV and Camplyobacter jejuni infections. These cases may have elevated antibody titers against GM2 and GM1 gangliosides respectively, both components of the axolemma.

It is now generally accepted that GBS has an autoimmune pathogenesis, involving both cellular and humoral mechanisms. Cytokines have an important pathogenetic role as evidenced by the correlation of tumor necrosis factor with severity of electrophysiologic abnormalities. Recent work has suggested that the abberant immune response in GBS may be directed against glycolipid components of the axolemma and myelin sheath. Antibodies to peripheral nerve constituents may activate the complement cascade and macrophages, resulting in antibody-dependent cellular cytotoxicity towards myelin or axolemma components. Preceding Camplyobacter jejuni infection may initiate an antibody response due to molecular mimicry between carbohydrate epitopes present in the axolemma and the bacteria's lipopolysaccharide coat.6

Electrodiagnostic studies are critical in documenting peripheral nerve dysfunction and establishing prognosis. Diffusely low amplitude motor potentials have generally been considered to be a poor prognostic sign due to their implication of motor axon degeneration. Recent studies have suggested that low amplitude motor potentials may alternatively reflect terminal nerve ending degeneration, rather than more diffuse axonal disease, and may not be such an ominous prognostic finding. Elevated CSF protein levels are common but may not be evident for a week or more after symptom onset. CSF pleocytosis is not present in GBS except with underlying HIV infection. Nerve biopsy is almost never needed for clinical purposes. Elevated anti-GM1 and anti-GQ1b antibodies, or CMV titers are usually not clinically useful.

Treatment of GBS should begin as quickly as possible to achieve maximum benefit. Plasma exchange (PE) initiated within 2 weeks of symptom onset hastens clinical improvement. Intermediate and severe cases require 4 exchanges of 1.5 plasma volumes but milder cases require only 2 exchanges. Additional exchanges are not beneficial. Intravenous immunoglobulin (IVIg) is equally, and possibly more effective than PE. The ease of administration and low side effect profile has made IVIg the preferred therapy. It is unclear if IVIg administration later than 2 weeks from symptom onset is effective. There is no proven benefit of combining IVIg and PE treatments. However, many clinicians utilize IVIg in patients who continue to deteriorate after an adequate course of PE. Conventional dosages of prednisone have been proven to be ineffective, but IVIg combined with high dose methyprednisolone may be beneficial. Clinical relapse after initial improvement may respond to repeat PE or IVIg.7 Attentive nursing care, early intubation for respiratory distress, and appropriate positioning and bracing remain the cornerstones of GBS care.

Acquired Chronic Demyelinating Neuropathies

Acquired chronic demyelinating neuropathies are more common than the acute types and represent up to 10-20% of initially unclassified PNs. The term chronic inflammatory demyelinating polyneuropathy (CIDP) refers to a group of PNs with subacute onset and a chronic course that is either continually or stepwise progressive, or relapsing-remitting. The underlying pathology is both demyelinating and axonal. Despite its name, inflammatory infiltrates in nerve biopsy specimens are minimal. Patients present with a mixture of motor and sensory deficits which are usually asymmetric in distribution. Although many patients have both distal and proximal sensorimotor deficits, the clinical picture can exactly mimic the distal predominant PNs common to most metabolic, toxic, and nutritional causes.8,9 In contrast to GBS, cranial nerve dysfunction and respiratory insufficiency is unusual. Peak onset occurs between ages 40-60 and childhood cases are unusual. Clinical clues to the demyelinating nature of the PN include:

  1. the onset of proximal before distal weakness;
  2. asymmetric, proximal greater than distal, or patchy sensory deficits;
  3. diffuse or proximal areflexia early in disease course; and
  4. early gait ataxia, especially when out of proportion to clinical proprioception loss.

A clinically pure sensory variant of CIDP has been described. Elevated CSF protein levels are frequent but LP and nerve biopsy are not usually needed to establish a diagnosis. EDx studies show a mixture of demyelination and axonal degeneration, with varying degrees of denervation in affected muscles.

CIDP is believed to be an immune mediated PN, but the provoking triggers and neural targets are uncertain. Most cases of CIDP do not have an identifiable underlying systemic illness, but some are associated with infections such as HIV and Lyme disease, lymphatic malignancies, systemic lupus erythematosis, Castleman's disease, and monoclonal paraproteinemias (see below). CIDP should be suspected in cases of progressive, subacute sensorimotor PNs with mixed demyelinating/axonal physiologic features, and no underlying systemic illness. Effective treatment is available for most patients and PE, IVIg, or prednisone results in improvement in about 95% of patients. Repeated therapy is often needed because of the high frequency of clinical relapses. Unlike AIDP, CIDP is often steroid responsive. Patients usually require initial dosages of 1-1.5 mg/kg on a daily basis. Once improvement is noted, usually within 4-8 weeks, alternate day dosing can be initiated. PE is effective in up to 80% of patients but is limited by the need for in-patient administration. Initially 2-3 exchanges are administered with repeat exchanges if the patient relapses. Almost 2/3 of patients with CIDP initially respond to IVIg. The ability to administer IVIg out of hospital and its few serious side effects make it the initial treatment of choice. Initial administration of 2 gm/kg in divided doses over 2 or 5 days often results in remarkable resolution of even long-standing deficits. Monthly repeat administration with a booster dose of 1-1.5 gm/kg over 1-2 days is often needed. Long term consequences of repeated IVIg administration are not certain and patients occasionally become refractory to treatment. IVIg responsiveness may occasionally be restored by intense PE treatment followed by a high dose IVIg booster (2 gm/kg). IgA deficient patients require IgA depleted immunoglobulin to avoid anaphylaxis. Minor side effects such as headache, rash, and myalgias can be ameliorated with pretreatment with either aspirin, benadryl, or prednisone. More serious complications such as renal failure and stroke have been reported, most frequently in patients with either underlying renal insufficiency or migraines. Clinically refractory cases may respond to cyclosporin A and interferon alpha-2a. Other immunosuppressives such as azathioprine and cyclophosphamide have not been definitely proven effective.

Multifocal Motor Neuropathy

Multifocal motor neuropathy (MMN) is a recently described motor neuropathy which may be a variant of CIDP. Distal, asymmetric limb weakness and wasting progresses insidiously over months to years.10 The arms are more frequently affected than the legs and there are prominent muscle cramps and fasciculations. DTRs may be lost in atrophic muscles, but spared elsewhere. Cranial nerve dysfunction is rare and respiratory function remains intact. Patients are often oblivious to the degree of their weakness because of the insidious progression. The diagnosis is not difficult if the condition is kept in mind as few other illnesses have the marked, "cadaver" like hands, without sensory loss or pain, and chronic course. The differential diagnosis includes distal spinal muscular atrophies, lower motor neuron form of ALS, multiple entrapment neuropathies (although the normal sensory function is much against this), and CIDP. Electrodiagnostic studies classically show areas of motor conduction block in nerve segments not prone to compression. Sensory potentials are usually spared and needle EMG shows a marked degree of active and chronic denervation.11 Occasional cases of clinically certain MMN have been reported without demonstrable motor conduction block. High titers to GM1 gangliosides are supportive of MMN but are not essential to the diagnosis and are not predictive of response to therapy. CSF protein is frequently normal. The response to immunomodulating therapy is variable. IVIg may be effective but usually requires repeat administration to sustain improvement. Treatment should be continued for many months before deeming it ineffective. Oral prednisone and PE are not usually effective. Intravenous cyclophsophamide (3 g/m2 in 5 divided doses over 8 days) followed by oral administration (2 mg/kg/d) is also effective. The decision to use cyclophosphamide depends on the severity of the deficits, IVIg ineffectiveness, and the patient's intolerance of the motor deficits.

Paraprotein Related Neuropathy

Paraprotein related neuropathy is responsible for about 10% of initially unclassified PNs. Monoclonal proteins, usually IgM, IgG, or IgA with either kappa or lambda light chains have been implicated.12 Identification of the monoclonal protein is important because of its association with potentially serious medical illnesses such as multiple myeloma, lymphoma, amyloidosis, or Waldenstrom's macroglobulinemia. In 2/3 of patients with monoclonal proteins, no underlying systemic illness is found, a condition called monoclonal gammopathy of undetermined significance (MGUS). This term is somewhat of a misnomer however, as long term follow-up has demonstrated that 25-33% of MGUS patients eventually develop a malignant plasma cell dyscrasia. Monoclonal gammopathies, either IgG or IgA, have also been associated with osteosclerotic myeloma, which differs from classic multiple myeloma by its earlier age of onset, lack of systemic features (uremia, hypercalcemia, bone pain), sclerotic rather than lytic bone lesions, and a greater frequency of accompanying PN. Plasmacytomas may be multiple or solitary. The PN is similar to CIDP with symmetric, predominately motor deficits, intact cranial nerve and respiratory function, and demyelinating or mixed demyelinating/axonal features on EDx. Associated symptoms of organomegaly, skin changes, and endocrinopathy constitute the POEM syndrome. A skeletal survey, but not bone scan, often demonstrates the sclerotic bone lesions.

Monoclonal gammopathies are identified by quantitative immunoglobulin studies along with either serum immunofixation or immunoelectrophoresis to characterize the heavy and light chains. Serum protein electrophoresis alone is inadequate, as a small elevation of monoclonal protein may be obscured in the gamma globulin region. Identification of urinary Bence Jones protein is useful in diagnosing multiple myeloma. Hematologic evaluation, including bone marrow exam, is often necessary to exclude malignacy and establish the MGUS condition.

The pathology of monoclonal protein PNs is heterogeneous and includes demyelinating, mixed demyelinating/axonal, and exclusively axonal varieties. IgM and IgG paraproteins have been most closely associated with PN; the pathogenetic role of IgA is less certain. MGUS patients tend to have distal symmetric sensorimotor or predominantly sensory, occasionally painful PNs that are slowly progressive. Median age of onset is 6th decade and there is a male predominance. In comparison to IgG, IgM MGUS tends to have greater ataxia, more demyelinating features on EDx studies, and in 50% of cases, antibodies to myelin associated glycoprotein (anti-MAG antibodies).

The decision to treat MGUS PN depends on the degree and nature of the clinical deficit, its progression, the patients' general medical condition, their tolerance of the disability, and their age. PE and IVIg have both been reported to be effective in some cases. However, there is great variability in clinical response, and often no relationship to changes in the quantity of monoclonal protein. IVIg is probably more effective than PE for IgM PN. The presence of anti-MAG antibodies has been associated with a more refractory course.

Diabetic Neuropathy

Diabetic PN is now the most common PN worldwide. More than 50% of diabetics will eventually develop PN, the exact incidence dependent on the sensitivity of the diagnostic criteria and the duration of diabetes. Diabetic PN has many forms, the most common being a distal sensory or sensorimotor variety. Other presentations include an acute, asymmetric or bilateral painful motor neuropathy predominantly affecting proximal leg muscles; truncal neuropathy (thoracic polyradiculoneuropathy); cranial neuropathy (mostly CN III and VI); and an autonomic neuropathy which may have an associated sensory PN. Only the generalized sensorimotor, and proximal motor neuropathy will be addressed here.13

Generalized PN from diabetes usually begins insidiously, although its course is variable. While rarely disabling because of weakness or ataxia, it is often painful, especially when walking or at night. Occasionally the feet are markedly dysesthetic. In general, positive sensory symptoms of pain, burning, and paresthesias are more bothersome than weakness or numbness. However, profound sensory loss is an important factor in the genesis of diabetic foot ulcers, the major cause of non-traumatic limb amputations. PN tends to occur in established diabetics and tends not to precede serum glucose abnormalities or occur in newly diagnosed diabetics. In such patients, alternative non-diabetic etiologies should be vigorously sought. Although the pathogenesis of diabetic PN remains uncertain there appears to be a role for oxidative stress as a link between metabolic and ischemic injury. Persistent hyperglycemia leads to activation of the aldose reductase and sorbitol dehydrogenase pathway, depleting NADPH. The result is reduced glutathione and nitric oxide activity. Reduced glutathione activity may disrupt mitochondrial DNA, resulting in release of free radicals and oxidative damage to nerves. Reduced nitric oxide activity reduces nerve blood flow, thereby limiting the nerve's ability to buffer free radicals. These oxidative stresses may play a role in programmed cell death which may, in part, underlie the clinical PN.14

Pain treatment often evolves into a trial and error regimen. In my experience, the following are most effective, in descending order of usefulness: tricyclic antidepressants (Pamelor® more than Elavil®), Neurontin®, Ultram®, and other anticonvulsants such as Dilantin®, Tegretol®, and recently Lamictal®. Dosages need to be pushed to maximum or until intolerable side effects occur before deeming therapy ineffective. Patients with significant pain who do not respond to the above often benefit from pain management specialists. Patients need to examine their feet daily and any beginning ulcers should be aggressively treated. Strict glucose control, either by exogenous insulin or pancreatic transplant, remains the only proven therapy in retarding the development and progression of PN.15

Proximal motor neuropathy, formerly called diabetic amyotrophy, is less common than the generalized sensorimotor form but is extremely disabling. Weakness and atrophy affects the proximal leg muscles, either unilaterally or bilaterally. Occasionally, the proximal weakness is accompanied by substantial distal weakness. The disparity between weakness and sensory loss is striking and serves as an important clue to the diagnosis. Pain is prominent and although it may continue up to a year, it usually resolves spontaneously in a few weeks to months. Diabetic proximal motor PN is most common in type II diabetics and unlike the generalized PN, may precede the diagnosis of diabetes. Arm weakness may rarely accompany leg weakness and weakness may become so severe that the patient is bed bound. The pathogenesis of these conditions was thought to be ischemia in the asymmetric variety, and metabolic in the bilateral form. Many now feel that the different presentations are variants of the same condition and have a similar pathogenesis. Sensory nerve biopsies have revealed inflammatory infiltrates, suggesting an immune or inflammatory component. IVIg has produced clinical improvement in some patients, although its use is not routine. Differential diagnosis predominantly involves compressive L3,4 radiculopathies, or lumbosacral plexopathies.16

Painful Axonal Idiopathic Neuropathy (PAIN)

Possibly the second most common PN, aside from diabetic, now being referred for neuromuscular evaluation is a painful, sensory PN of uncertain etiology. Anecdotal reports from multiple sites have detailed a rather homogenous clinical picture of a middle age or older patient, more often female, with a slowly, progressive, painful PN, affecting primarily the feet. The soles are often the initial site of involvement and the process appears relatively symmetric. Pain is often of the burning quality and is often unremitting, especially at night. Complaints of weakness, ataxia, autonomic or cranial nerve dysfunction, are conspicuously absent. Clinical exam shows distal loss of pin and temperature with relative preservation of vibratory and proprioceptive function. DTRs are intact and weakness is not present. The course is slowly progressive, usually confined to the legs except for rare occasions, and unassociated with systemic illness. EDx shows normal sensory and motor function, consistent with predominant involvement of small afferent fibers. Active denervation can occasionally be found in the intrinsic foot muscles.17 Quantitative sensory testing, using computer-assisted instrumentation to quantitate sensory thresholds often confirms the clinical exam by documenting threshold elevations to cold and heat-nociception. Autonomic symptoms and laboratory abnormalities are lacking. Skin biopsy may show a reduction in the number of intraepidermal nerve fibers.

PAIN is differentiated from other painful PNs by noting the restricted involvement of small afferent fibers, normal strength and DTRs, and normal EDx studies. Most other painful sensory neuropathies show both large and small fiber involvement and therefore nerve conduction studies are abnormal. Consideration needs to be given to PNs from Sjogren's syndrome, vasculitis, amyloidosis, MGUS, and diabetes. The consistency of the clinical picture, without the appearance of new deficits over time, supports the diagnosis. At present, treatment centers around pain management, similar to that described for diabetes. Neurontin has proven to be of particular benefit in these patients, although the dosage needs to be maximized as tolerated.

Hereditary Sensory Motor Neuropathy

Hereditary motor and sensory neuropathy (HMSN) or Charcot Marie Tooth disease (CMT) is a heterogeneous group of disorders. These genetically based neuropathies are common, with estimates as high as 1 in 2500 people being affected by some form. Most of the hereditary PNs are autosomal dominant in inheritance pattern although there are X-linked and recessive forms. There is a wide range of clinical severity in CMT. Some patients are essentially asymptomatic and only have pes cavus deformity and hammer toes while others have prominent weakness beginning in the legs, along with distal sensory loss. The deficits tend to progress slowly over time and many patients will eventually have difficulty ambulating due to foot drop. The typical age of onset is in the third or fourth decade. Physical examination demonstrates reduced or absent DTRs, distal sensory loss, and weakness. There may be prominent distal muscle wasting that is referred to as an inverted champagne bottle appearance. Pain is a distinctly unusual symptom and its presence argues against a hereditary PN. EDx helps to distinguish the demyelinating forms of CMT from those that are axonal. This distinction is important when considering tests for the underlying genetic defect.

Of the hereditary PNs, autosomal dominant CMT1 is the most common. In the past, the diagnosis of CMT1 was based on the clinical findings of palpable nerves, diffuse areflexia, a positive family history, and prominent slowing of conduction velocities on EDx. Nerve biopsies demonstrate "onion bulb" formation which refers to nerve fibers surrounded by concentric layers of material due to demyelination and remyelination. Onion bulbing is the underlying cause for the palpable thickening of nerves commonly seen with CMT1. Genetic testing is now available commercially and provides a definitive diagnosis of most cases of CMT 1. There are several subtypes of CMT1 based on the gene affected. CMT1A is a demyelinating PN due to duplication of the PMP-22 (peripheral myelin protein) gene on chromosome 17 and is the most common. CMT 1B is due to point mutations in the P0 gene on chromosome 1. Another form of demyelinating neuropathy that is indistinguishable from CMT1 is CMTX. This results from a defect in the connexin-32 gene on the X chromosome causing a demyelinating neuropathy. This can be distinguished by the pattern of inheritance (absence of male to male transmission) and the genetic test is also available.18

The axonal form of hereditary PN is designated CMT2. This PN is also inherited in an autosomal dominant fashion. Compared to CMT1 there tends to be a later age of onset, less motor weakness until late in the course, normal nerve conduction velocities and no onion bulb formation or thickening of nerves. The underlying genetic defect is not well defined although some companies are offering testing that is of questionable value.

Another genetic PN is hereditary neuropathy with liability to pressure palsy (HNPP). The clinical phenotype, as the name suggests, is that of multiple compression neuropathies, especially in unusual locations or nerves that are not typically subject to entrapment. The degree of penetrance may vary from one generation to the next making the inheritance pattern (autosomal dominant) less obvious. Nerve conduction studies often show evidence for a demyelinating PN with much more prominent slowing at sites of entrapment. HNPP is caused by deletion of the same PMP-22 gene that causes CMT1A. Thus, there is an interesting dose-response relationship of the PMP-22 gene; an extra copy results in CMT1A while a missing copy causes HNPP.18

As hereditary PN are so common, one should always keep that possibility in the differential diagnosis when a patient presents with symptoms or signs of PN. Greater than 40% of undiagnosed, referred PNs in the Mayo series were found to be genetic in nature. The key points in the evaluation include:

  1. A very thorough family history and, if possible, examination of family members who may be asymptomatic;
  2. Palpable nerves, areflexia or evidence of entrapment neuropathies on exam;
  3. Electrodiagnostic studies to classify the neuropathy as axonal or demyelinating;
  4. Genetic testing when appropriate.

No treatment for the underlying PN is available but the provision of assistive devices (e.g. ankle foot orthoses) can be very helpful.

Summary

In summary, there are numerous etiologies of PN. The purpose of this article was to describe the current understanding of pathogenesis and treatment for some of the more common forms of PN. Diagnosis of the underlying cause is difficult and dependent on the combination of a directed history and physical examination, EDx studies, and a selected laboratory work-up. Treatment of the underlying cause may be possible if the correct diagnosis is established. At minimum, symptom management and better understanding by the patient of what to expect in the future can be achieved even if the progression cannot be halted.

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Jacksonville Medicine / August, 2000
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