text: Clinical uses EMG testing has a variety of clinical and biomedical applications. Needle EMG is used as a diagnostics tool for identifying neuromuscular diseases, or as a research tool for studying kinesiology, and disorders of motor control. EMG signals are sometimes used to guide botulinum toxin or phenol injections into muscles. Surface EMG is used for functional diagnosis and during instrumental motion analysis. EMG signals are also used as a control signal for prosthetic devices such as prosthetic hands, arms and lower limbs.
  An acceleromyograph may be used for neuromuscular monitoring in general anesthesia with neuromuscular-blocking drugs, in order to avoid postoperative residual curarization (PORC).
  Except in the case of some purely primary myopathic conditions EMG is usually performed with another electrodiagnostic medicine test that measures the conducting function of nerves. This is called nerve conduction study (NCS).   Needle EMG and NCSs are typically indicated when there is pain in the limbs, weakness from spinal nerve compression, or concern about some other neurologic injury or disorder. Spinal nerve injury does not cause neck, mid back pain or low back pain, and for this reason, evidence has not shown EMG or NCS to be helpful in diagnosing causes of axial lumbar pain, thoracic pain, or cervical spine pain.  Needle EMG may aid with the diagnosis of nerve compression or injury (such as carpal tunnel syndrome), nerve root injury (such as sciatica), and with other problems of the muscles or nerves. Less common medical conditions include amyotrophic lateral sclerosis, myasthenia gravis, and muscular dystrophy.
  Technique
  Skin preparation and risks
  The first step before insertion of the needle electrode is skin preparation.  This typically involves simply cleaning the skin with an alcohol pad.