2022 Workshop Handout Bundle-Myopathies: EDX Approach- Kushlaf

Myopathies: EDX Approach- Kushlaf
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The electrodiagnostic (EDX) approach to diagnosing myopathies varies depending on the clinical presentation. Patients are typically referred to the EDX laboratory with symptoms such as muscle weakness, elevated creatine kinase levels, abnormal lab results, muscle stiffness, muscle pain, rhabdomyolysis, muscle twitching, or muscle atrophy. The clinical examination may reveal patterns of weakness, and the EDX study can show abnormalities suggestive of a myopathy. However, a muscle biopsy is still needed to confirm the diagnosis and rule out other potential causes.<br /><br />The EDX study should take into consideration the patient's symptoms and exam findings, with a focus on weak muscles. Specific protocols, such as short or long exercise testing or repetitive nerve stimulation, may be used for certain conditions. Nerve conduction studies are typically performed to confirm the diagnosis, assess the severity of the myopathy, and determine the distribution of affected muscles. Sensory nerve conduction studies are usually normal, while motor nerve conduction studies may show abnormalities in myopathies that affect distal muscles.<br /><br />Needle electromyography (EMG) is another important component of the EDX evaluation. Weak muscles should be examined, and a variety of muscles may be sampled to account for the patchy nature of myopathies. Spontaneous activity and motor unit action potentials (MUAPs) are assessed during needle recordings. Abnormalities such as decreased insertional activity, muscle rippling, contractures, and abnormal MUAP morphology can be indicative of myopathy. Decreased MUAP duration and early recruitment are reliable findings in myopathies.<br /><br />Overall, the EDX approach to diagnosing myopathies involves a combination of clinical evaluation, nerve conduction studies, and needle EMG. It is important to consider the patient's symptoms, select relevant muscles for examination, and interpret the findings in the context of the presenting clinical picture.<br /><br />References:<br />1. "Myopathies: An Electrodiagnostic (EDX) Approach" - Workshop by Dr. Hani Kushlaf at the AANEM Workshop.<br />2. Z'Graggen, W., & Tankisi, H. (2020). Critical Illness Myopathy. J Clin Neurophysiol. doi:10.1097/WNP.0000000000000652.<br />3. Stålberg, E., et al. (2019). Standards for quantification of EMG and neurography. Clin Neurophysiol, 130(9), 1688-1729. doi:10.1016/j.clinph.2019.05.008.<br />4. Lacomis, D. (2012). Electrodiagnostic approach to the patient with suspected myopathy. Neurol Clin, 30(2), 641-660. doi:10.1016/j.ncl.2011.12.007.<br />5. Daube, J. R., & Rubin, D. I. (2009). Needle electromyography. Muscle Nerve, 39(2), 244-270. doi:10.1002/mus.21180.<br />6. Petajan, J. H. (1991). AAEM minimonograph #3: motor unit recruitment. Muscle Nerve, 14(6), 489-502. doi:10.1002/mus.880140602.
Keywords
electrodiagnostic approach
myopathies
muscle weakness
creatine kinase levels
muscle stiffness
rhabdomyolysis
nerve conduction studies
needle electromyography
muscle biopsy
clinical evaluation
ncs