Clinical neurophysiology of anterior horn cell disorders

The development of neurophysiological techniques for clinical assessment in the 20th century is closely related to the study of anterior horn cell diseases. The effects of motor axon loss on nerve conduction velocity and compound motor amplitude were elucidated first in amyotrophic lateral sclerosis (ALS), as was the characterization of reinnervation as detected by needle electromyography. The same changes noted in early studies still play a major role in the diagnosis of anterior horn cell diseases. In addition, much of modern neurophysiological assessment of motor axon quantitation, ion channel changes in neurogenic disease, and cortical physiology studies to assess both network and excitability abnormalities have all been applied to ALS. In this chapter, we summarize the clinical attributes of ALS and Spinal Muscular Atrophy, and review how clinical neurophysiology is employed in the clinical and the research setting.