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Publisher Summary This chapter discusses a variety of available approaches for testing the autonomic nervous system and their technical and methodological limitations. The discussion is complete but not exhaustive, and the focus is on techniques that have been used in clinical contexts or show particular promise for clinical use. The current understanding of the clinical relevance of autonomic dysfunction followed the development of autonomic testing and its application to clinical populations. It is now apparent that autonomic testing predicts prognosis in patients with diabetes, identifies some patients with asymptomatic myocardial ischemia, and correlates with fatigue and impaired exertional capacity in a variety of medical and neurological disorders. Several simple clinical tests can also be performed in the EMG laboratory. Simply measuring the blood pressure response to sitting and standing is perhaps the most informative clinical test of autonomic function. Skin wrinkling and pressor response to ice water immersion or handgrip are other simple tests that can provide a rapid screening of autonomic function as well.

Over the last two decades significant advances in ultrasound have made it possible for investigators to image and interpret pathologic changes in muscle and nerve. In addition to being able to assess the pathologic changes in these structures themselves, ultrasound also provides the unique ability to identify anatomic lesions responsible for nerve or muscle injury. They can be correlated with changes in neural structures or affected muscles. Like electrodiagnostic studies, ultrasound is portable and inexpensive, but it is even less invasive, and surprisingly sensitive in detecting a variety of unusual and common causes of neuromuscular dysfunction. Given recent developments in the field, ultrasound shows promise as the technique most suitable for clinical neurophysiologists and neuromuscular clinicians in the growing field of imaging. Such involvement is required to best adopt and exploit the potential of imaging for the research and clinical evaluation of neuromuscular disorders.