Common Symptoms

EMG Advantages and Limiting Factors

Advantages

• Only laboratory study that directly assesses the physiologic integrity of the roots , thereby providing both diagnostic and prognostic relevance
• Objective : May reveal changes consistent with a root lesion in the presence of a normal/unsatisfactory physical exam
• The EDX evaluation may be abnormal when all other laboratory procedures, including neuroimaging studies, are unrevealing. EDX is therefore helpful with non-compressive radiculopathies, when imaging is inconclusive
• With definite compressive root lesions, EDX can determine the severity of the axon loss, helping to gauge the relevance of any positive imaging findings
• EDX can identify extraforaminal lesions e.g. plexopathies, mononeuropathies, polyneuropathies, the symptoms of which are often attributed incorrectly to radiculopathies
• When performed by experienced physicians, EDX studies are rarely false positive. In contrast, incidental neuroimaging abnormalities are very common, particularly in the middle-aged or elderly patients without related symptoms. Consequently, EDX studies may be helpful in determining whether the imaging is of clinical significance
• EDX studies have a low morbidity

Limiting Factors

• Does not detect all compressive radiculopathies. EDX cannot be used to exclude a radiculopathy.
• When a radiculopathy is suggested, the etiology cannot be determined.
• When a specific root appears to be involved, various anatomic factors may lead to inaccurate localization, so the affected root is not recognized (usually the one adjacent)
• Confounding actors: patient age, diabetes mellitus, generalized polyneuropathy, remote poliomyelitis

More information:

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