Diagnosis of a neuromuscular disorder is made on the basis of physical and neurologic examination, laboratory testing, electrophysiology, and biopsy. Electrophysiologic evaluation of nerve and muscle disorders is usually only performed at specialist centers. Muscle and nerve biopsy and additional laboratory tests are discussed in Chapter 2 (for laboratories see p. 334, 1-3). Neurologic examination should provide a clear distinction between neuropathies and myopathies. Hyporeflexia or arreflexia and possible impairment of sensory pain perception are distinguishing features of neuropathies and are not seen with myopathies or junctionopathies. The distinction between myopathy and junctionopathy may be more difficult to make. Myasthenia gravis, in particular, may produce signs that mimic those of a generalized myopathy, although it is a junctionopathy.