Following completion of this chapter, the student will be able to:
- Define and describe the anatomic and physiologic basis of clinical electrophysiologic testing (neural conduction and electromyographic [EMG] studies).
- Given a patient with a neuromuscular dysfunction, evaluate the appropriateness of requesting clinical electrophysiologic testing (neural conduction and electromyographic studies), and describe the specific additional information that would be provided by this testing, if ordered.
- Describe the basic role of each of the following pieces of equipment in routine electrophysiologic testing: electrodes (needle, reference, and ground), differential amplifiers, oscilloscope, audio speakers, stimulator, electrophysiologic processing unit, and printer.
- Discuss why nerve conduction studies (NCS) assess both sensory and motor fibers within a nerve, the information obtained from these tests, and the reason why sensory studies are typically assessed in microvolts, while motor studies are typically assessed in millivolts.
- Explain the role of latency, shape, amplitude, and nerve conduction velocity (NCV) in a NCS. Within this explanation, compare and contrast the information provided by normal and abnormal findings.
- Describe a “central conduction study” (F-wave) physiologically and the information provided by this portion of the examination.
- An H-wave (Hoffman's reflex) can only be elicited in select sites in the upper and lower extremities. Explain why this testing procedure cannot be applied universally, identify the specific regions where this test is appropriate, and discuss the additional information that it provides to the clinical electrophysiologist.
- Identify the type of nerve conduction evaluation that is particularly useful with conditions affecting the neuromuscular junction, such as myasthenia gravis and Lambert–Eaton syndrome. For each of these conditions, describe the anticipated neurophysiologic results.
- List and describe the four basic components of the electromyographic study (needle evaluation) outlined in this chapter. Within the description, identify the type of information that can be obtained from each component.
- While pathologic states often represent conditions that cause some damage to both myelin and axons, the pattern of damage is often predominantly demyelinating or axonal. Compare and contrast the electrophysiologic findings demonstrated in a primarily demyelinating condition (e.g., entrapment syndrome such as carpal tunnel syndrome) with a primarily axonal condition (e.g., radiculopathy).
- Compare and contrast anterior primary rami (APR) and posterior primary rami (PPR). Include in your discussion the anatomic and functional differences of the APR and PPR. In addition, discuss the importance of performing needle EMG examination of the paravertebral muscles (PVM) in a patient with a suspected radiculopathy.
- Describe the specific electrophysiologic parameters associated with positive sharp waves (PSWs) and fibrillation potentials, and discuss what these abnormal spontaneous electrical potentials represent physiologically.
- Given a patient who is suspected of having a myopathic disease (e.g., dermatomyositis), describe the type of electrophysiologic findings that would be present if this muscle disease was validated.
- The EMG obtained from single motor units provides indirect information regarding the status of structures such as the axon, neuromuscular junction, and innervated muscle fibers. Recognizing that there is variability inherent in the shape of single motor unit EMG, describe what constitutes abnormal findings ...
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