A 7-year-old girl visited the outpatient clinic because of difficulty walking. She had never managed to run properly, and experienced frequent falls ever since she began walking independently at the age of 18 months. Jumping was not possible, and when stepping up or down, she needed support below her arms. There was no fluctuation of symptoms during the day, but she had suffered from periods that could last several weeks in which using the stairs was completely impossible. She was unable to blow up a balloon and her speech was slow and poorly articulated. There were no complaints about chewing or swallowing. She had a healthy non-identical twin sister and the family history was unremarkable.

Electrodiagnostic studies are often at the centre of diagnostic strategies in neuromuscular disorders. The basic electrophysiological techniques commonly used are focused on documenting sufficient proof of dysfunction emanating from different parts of the peripheral nervous system: peripheral motor neuron, nerve root, plexus and peripheral nerve, neuromuscular junction, and skeletal muscle. In short, dedicated nerve conduction studies and needle myography or a combination of these may be needed to help accurately identify the site and nature of the neuromuscular disorder (Fig. 4.1A–C). Appropriate and standardized instrumentation, including control of temperature and uniform sampling, is essential for meaningful interpretation. The electrodiagnostic techniques aligned with the main anatomical correlates underlying different neuromuscular disorders are discussed in this chapter.