Assessment in Occupational Therapy and Physical Therapy, julia ven deusen

CHAPTER 9 Eleotrodiagnosis of the Neuromuscular System Edward J. Hammond, PhD SUMMARY In this chapter, traditional electrodiagnostic studies including nelVe con­ duction velocity studies, the electromyogram, and somatosensory evoked potential are sUlVeyed. Newer techniques, the motor evoked potential, the surface EMG, and dermatomal evoked potentials, are also considered. Detailed technical consider­ ations and interpretations are not discussed, but emphasis is placed on assisting the nonelectrophysiologist in understanding basic prinCiples of, and indications for, commonly used diagnostic tests. Limitations and benefits of each technique are clearly stated, and areas for future improvement and research are discussed. The anatomic system of interest in clinical electrodiagnosis consists of the pe­ ripheral nelVes, the neuromuscular junction, the skeletal muscles, and the soma­ tosensory and motor pathways in the spinal cord and brain. During normal move­ ments, these components interact with each other to bring about the contraction and relaxation of muscle. Various types of electrodiagnostic tests discussed in this chapter can be used to determine physiologic abnormalities occurring in one of these anatomic subdivisions. Historically, specific electrodiagnostic tests were devel­ oped because careful clinical examination is sometimes not enough for accurate diagnosis (and, therefore, treatment). The degree to which electrodiagnostic tests are pertinent to diagnosis and treatment depends on the extent to which we can in­ tegrate this \"subclinical neurology\" with clinical neurology. This chapter discusses basic principles, limitations, and benefits of currently used electrodiagnostic tests. Tests of peripheral nelVes and muscles are discussed first, then central nelVous sys­ tem testing. The chapter necessarily contains many technical and specialized terms, and the reader unfamiliar with electrophysiologic terminology is urged to consult the glossary at the end of the chapter. 1