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Electrodiagnostic testing, which includes nerve conduction studies (NCS) and needle electromyography (EMG), can support the diagnosis of peripheral neuropathy. This activity reviews some of the causes of peripheral neuropathy and the corresponding electrodiagnostic findings. It also reviews the technique for planning an electrodiagnostic study to evaluate peripheral neuropathy. It explains the interdisciplinary team's role in evaluating and improving care for patients who suffer from peripheral neuropathy. Objectives: Identify the indications for electrodiagnostic testing in patients with symptoms of peripheral neuropathy. Evaluate the nerve conduction study (NCS) findings in a patient with peripheral neuropathy. Assess the electromyographic (EMG) findings in a patient with peripheral neuropathy. Communicate the importance of communication among the interdisciplinary team to enhance care delivery for patients with peripheral neuropathy. Access free multiple choice questions on this topic.

Peripheral neuropathy, also known as peripheral polyneuropathy, is a general term for a broad range of disorders that cause damage and dysfunction of the nerves of the peripheral nervous system in several different patterns.[1] Electrodiagnostic (EDX) testing can not only identify whether or not peripheral neuropathy may be present. Still, it can also help give the clinician information to determine the disorder's etiology, severity, and prognosis. Thorough history taking, physical examination, and EDX are all integral to the evaluation and treatment of patients presenting with symptoms of peripheral neuropathy. Although peripheral polyneuropathies are commonly found in patients with diabetes mellitus or excessive alcohol use, many medical conditions have associations with peripheral neuropathies. Peripheral polyneuropathies can be acquired, such as in diabetes mellitus, amyloidosis, HIV, or cis-platinum chemotherapy, while some may be inherited, as in Charcot-Marie-Tooth.[2] Common symptoms of most peripheral polyneuropathies involve paresthesias, numbness, or pain in the distal extremities, such as in the feet or hands. Some can present acutely, while many have a more insidious onset. A patient may describe difficulty with buttoning their clothes or tripping over their feet, which may be signs of worsening weakness and progression of the disease. Inherited polyneuropathies may present with ataxia and muscle cramping, while acquired polyneuropathies typically present as burning or paraesthesias.[1]

Common symptoms of most peripheral polyneuropathies involve paresthesias, numbness, or pain in the distal extremities, such as in the feet or hands. Some can present acutely, while many have a more insidious onset. A patient may describe difficulty with buttoning their clothes or tripping over their feet, which may be signs of worsening weakness and progression of the disease. Inherited polyneuropathies may present with ataxia and muscle cramping, while acquired polyneuropathies typically present as burning or paraesthesias.[1] EDX can be useful in finding an etiology and thus guiding treatment. Therefore, obtaining a detailed history, including medications, diet, social/occupational history, and family history is critical. Exposure to heavy metal toxins or certain medications, such as vincristine and amiodarone, or a medical history significant for hypothyroidism or vitamin b12 deficiency indicate a risk for developing peripheral polyneuropathies. Patients with a family history of hereditary motor and sensory neuropathies (HMSN) such as Charcot-Marie-Tooth Type 1 disease (HMSN I) or Refsum’s disease (HMSN IV) might point the clinician toward a hereditary cause for the neuropathy. Infectious diseases such as Lyme disease and HIV and autoimmune-mediated diseases such as acute inflammatory demyelinating polyneuropathy or chronic inflammatory demyelinating polyneuropathy can also present with symptoms of peripheral neuropathy.[3]

EDX can be useful in finding an etiology and thus guiding treatment. Therefore, obtaining a detailed history, including medications, diet, social/occupational history, and family history is critical. Exposure to heavy metal toxins or certain medications, such as vincristine and amiodarone, or a medical history significant for hypothyroidism or vitamin b12 deficiency indicate a risk for developing peripheral polyneuropathies. Patients with a family history of hereditary motor and sensory neuropathies (HMSN) such as Charcot-Marie-Tooth Type 1 disease (HMSN I) or Refsum’s disease (HMSN IV) might point the clinician toward a hereditary cause for the neuropathy. Infectious diseases such as Lyme disease and HIV and autoimmune-mediated diseases such as acute inflammatory demyelinating polyneuropathy or chronic inflammatory demyelinating polyneuropathy can also present with symptoms of peripheral neuropathy.[3] The physical examination may also assist in identifying the etiology and characteristics of peripheral neuropathy. Patients with diabetic peripheral neuropathy often describe a “stocking-glove” distribution of numbness in the hands and feet. Deafness, cataracts, or musculoskeletal deformities point toward a hereditary cause. A predominant sensory neuropathy may have decreased light touch or vibration sensation, while distal muscle weakness and decreased deep tendon reflexes may indicate a motor-predominant neuropathy.[3] For example, a patient on dapsone therapy may present with weakness and abnormal deep tendon reflexes and has electrodiagnostic findings of primarily axonal motor neuropathy.[4] A patient who had high dose cis-platinum therapy may have preserved deep tendon reflexes and muscle strength but complained of abnormal sensation, as well as other drug side effects such as ototoxicity and gastrointestinal upset. In cis-platinum peripheral neuropathy, EDX often yields the presence of a primarily axonal sensory neuropathy.[5]

The risk of complications in both nerve conduction study and EMG needle examinations is rarely severe. Electrical stimulation does not usually cause any permanent or even temporary damage to the nerves tested. As with any needle stick procedure, there is a risk of infection or bleeding with needle insertion during the EMG; however, the risk is minimal with proper antiseptic and pressure techniques. Most patients find the electrical stimulation NCS studies uncomfortable but tolerable. At times, a patient may be unable to tolerate the examination due to the unpleasant “shock” sensation, needle exam, or, very rarely, a vasovagal episode. The patient may take breaks during the exam or reschedule the exam for another date. Usually, preparing patients ahead of time regarding what to expect and instructing them to eat and drink before the exam can help avoid these complications.[14]

Peripheral polyneuropathies can be encountered in many clinical settings regardless of specialty and cause significant morbidity to patients due to the accompanying pain, weakness, and deformity associated with them. In some estimates, its prevalence in the general population is 1 to 3% and increases to 7% in patients older than 50.[2] Internists, pediatricians, physiatrists, and neurologists must recognize the symptoms and risk factors associated with peripheral neuropathies and understand that further evaluation with EDX may assist with the diagnosis and treatment plan. Ideally, a thorough history by the primary care or referring physician should be performed, including past medical history, surgeries, medications used, diet, recreational drug or alcohol use, occupational exposures, and family history. The referring physician may start a diagnostic workup with blood work based on the working differential diagnosis to assist the electrodiagnostician. An interprofessional approach to patient care should be pursued, which would involve an open dialogue between the referring physician and the physician performing the EDX. Ideally, discussing any relevant history, physical, or lab findings before the EDX testing can help narrow down the differential and assist in planning the NCV and EMG studies. The electrodiagnostic results can help the referring physician decide whether to pursue additional studies, such as CSF analysis or nerve biopsy, to assist with the diagnosis and treatment plan.[1][11]