Abstract
Peripheral neuropathies are extremely common disorders and can come in many forms, ranging from single-episode autoimmune conditions, such as Guillain-Barré syndrome, to slowly progressive conditions without a clear etiology or due to a genetic mutation. The diagnosis is usually reached through a detailed history and clinical neurologic examination. Patients may complain of gait difficulties, pain in the distal lower extremities or frank weakness. On examination, distal sensory loss and weakness are usually present, with the lower extremities more affected than the upper. The physical examination is usually followed by directed serologic and electrophysiologic testing. In addition, in small-fiber neuropathy, a skin biopsy may help to confirm the diagnosis. Other conditions such as lumbosacral polyradiculopathy and myelopathy can occasionally masquerade as peripheral neuropathy. Once they are diagnosed, therapy may be focused on relieving symptoms and improving function. In some autoimmune neuropathies, effective immunomodulating treatments—including intravenous immunoglobulin, corticosteroids, and newer medications such as rituximab—may have a major impact on restoring function. Regardless of the specifics of etiology, a dedicated rehabilitation program can often help patients cope effectively with their impairments, even if pharmacologic therapy provides only limited benefit.
Keywords
Autoimmune, immunomodulation, peripheral neuropathy, polyneuropathy
| Synonyms | |
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| ICD-10 Codes | |
| G60.8 | Hereditary and idiopathic neuropathies |
| G60.3 | Idiopathic progressive neuropathy |
| M35.9 [G63] | Polyneuropathy in collagen vascular disease |
| E11.42 | Type 2 diabetes mellitus with diabetic polyneuropathy |
| D49.9 [G63] | Polyneuropathy in malignant disease |
| G62.9 | Polyneuropathy, unspecified |
| G62.1 | Alcoholic polyneuropathy |
| G62.0 | Drug-induced polyneuropathy |
| G62.2 | Polyneuropathy due to other toxic agents |
Definition
Peripheral neuropathies are a collection of disorders characterized by the generalized dysfunction of peripheral nerves. This group of diseases is heterogeneous, including those that predominantly affect the nerve axon, others that primarily affect the myelin sheath, and still others that involve both parts of the nerve simultaneously. In addition, some peripheral neuropathies affect only small, unmyelinated fibers, whereas others predominantly involve only large myelinated ones. Table 143.1 contains a list of the most frequently encountered forms of peripheral neuropathy.
| Predominantly Axonal Disorders |
| Diabetic neuropathy |
| Alcoholic neuropathy |
| Medication-related neuropathy (e.g., due to metronidazole, colchicine, nitrofurantoin, isoniazid) |
| Systemic disease–related neuropathy (e.g., chronic renal failure, inflammatory bowel disease, connective tissue disease) |
| Thyroid neuropathy |
| Heavy metal toxic neuropathy (lead, arsenic, cadmium) |
| Porphyric neuropathy |
| Paraneoplastic neuropathy |
| Syphilitic, Lyme neuropathy |
| Sarcoid neuropathy |
| Human immunodeficiency virus–related neuropathy |
| Hereditary neuropathies (Charcot-Marie-Tooth type 2; familial amyloid; mitochondrial) |
| Critical illness neuropathy |
| Predominantly Demyelinating Disorders |
| Idiopathic CIDP |
| CIDP associated with monoclonal proteins |
| Antimyelin-associated glycoprotein neuropathy (a form of CIDP) |
| Human immunodeficiency virus–associated CIDP |
| Idiopathic Guillain-Barré syndrome |
| Guillain-Barré syndrome secondary to known etiology (e.g., influenza, Campylobacter jejuni, Zika) |
| Hereditary (Charcot-Marie-Tooth types 1 and 3) |
Peripheral neuropathy is common; one Italian study suggested a prevalence of about 3.5% in the general population. In diabetes, one study demonstrated clinical peripheral neuropathy affecting 8.3% of individuals compared with a control population, in whom 2.1% of individuals were affected. After 10 years, 41.9% of the diabetic patients had peripheral neuropathy, compared with 6% of the control subjects.
Defining peripheral neuropathy remains no simple task; however, a formal case definition for distal symmetric polyneuropathy (the most common form) has been developed. This definition uses a combination of symptoms, signs, and electrodiagnostic testing results to formulate an ordinal ranking system to identify the likelihood of the disease in a given patient. Although it is a useful tool for future research studies, the necessity of applying such a complex approach underscores the difficulty in attempting to define peripheral neuropathy in any simple fashion.
Symptoms
Patients with peripheral neuropathy present with a number of specific sensory complaints, including decreased sensation that is often associated with pain, tingling (paresthesias), and burning. They may complain of a “sock-like” feeling in their feet or that their feet are persistently cold. Some patients, usually with more advanced disease, will note atrophy of the intrinsic foot muscles and some weakness, especially with the development of partial footdrop. Walking difficulties usually also develop once sensation is significantly impaired. Sensory symptoms in the hand (paresthesias and reduced tactile sensation) usually develop once an axonal peripheral neuropathy has progressed up to about the level of the knees. In patients with generalized demyelinating peripheral neuropathies, more generalized symptoms of weakness and sensory loss are often present, although distally predominant paresthesias often occur. History taking should include a detailed review of current and past medical issues, review of systems, and any exposure to toxins ( Table 143.2 ).
| Industrial Chemicals |
| Affect peripheral nervous system preferentially |
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| Some effects on central nervous system |
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| Large amounts required |
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| Some effects on other than nervous tissue |
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| Pharmaceutical Substances |
| Arsenic |
| Arsenic-based chemicals |
| Clioquinol |
| Disulfiram |
| Gold |
| Hydralazine |
| Nitrofurantoin |
| Phenytoin |
| Sulfonamides |
| Thalidomide |
| Thallium |
| Vincristine |
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